AI API aggregation platform with an OpenAI-compatible LLM endpoint for NLP tasks such as translation, summarization, multilingual generation, and structured extraction.
A curated list of resources dedicated to Natural Language Processing
This list covers natural language processing — linguistic analysis, multilingual tooling, classical and neural methods, datasets, and evaluation. Large language models are included only where they advance or evaluate a core NLP task or capability (tokenization, multilinguality, MT, summarization, NER, QA, factuality, probing, distillation). General-purpose chatbots, agent frameworks, prompt-template repositories, code-generation tools, and RAG application starter kits live in other lists — see See Also.
The Berkeley NLP Group - Notable contributions include a tool to reconstruct long dead languages, referenced here and by taking corpora from 637 languages currently spoken in Asia and the Pacific and recreating their descendant.
NLP research group, Columbia University - Responsible for creating BOLT ( interactive error handling for speech translation systems) and an un-named project to characterize laughter in dialogue.
Advanced NLP with spaCy - Free online course covering text processing, large-scale data analysis, processing pipelines, and training neural network models for custom NLP tasks.
Kaggle NLP Learning Guide - Beginner-friendly tutorials including getting started guides, deep learning for NLP, and visual explanations of techniques like BERT, GloVe, and TF-IDF.
Deep NLP Course by Yandex Data School, covering important ideas from text embedding to machine translation including sequence modeling, language models and so on.
fast.ai Code-First Intro to Natural Language Processing - This covers a blend of traditional NLP topics (including regex, SVD, naive bayes, tokenization) and recent neural network approaches (including RNNs, seq2seq, GRUs, and the Transformer), as well as addressing urgent ethical issues, such as bias and disinformation. Find the Jupyter Notebooks here
Applied Natural Language Processing- Lecture series from IIT Madras taking from the basics all the way to autoencoders and everything. The github notebooks for this course are also available here
DeepLearning.AI Natural Language Processing Specialization - 4-course program covering sentiment analysis, word embeddings, RNNs, LSTMs, attention mechanisms, and Transformer models like BERT and T5 for tasks including machine translation and summarization.
The Math Behind Artificial Intelligence - bt Tiago MOnteiro | A free FreeCodeCamp book teaching the math behind AI in plain English from an engineering point of view. It covers linear algebra, calculus, probability & statistics, and optimization theory with analogies, real-life applications, and Python code examples.
TextAttack - Adversarial attacks, adversarial training, and data augmentation in NLP
TextBlob - Providing a consistent API for diving into common natural language processing (NLP) tasks. Stands on the giant shoulders of Natural Language Toolkit (NLTK) and Pattern, and plays nicely with both :+1:
spaCy - Industrial strength NLP with Python and Cython :+1:
gensim - Python library to conduct unsupervised semantic modelling from plain text :+1:
scattertext - Python library to produce d3 visualizations of how language differs between corpora
GluonNLP(archived) - A deep learning toolkit for NLP, built on MXNet/Gluon.
AllenNLP(archived) - An NLP research library, built on PyTorch, for developing state-of-the-art deep learning models on a wide variety of linguistic tasks.
PyTorch-NLP - NLP research toolkit designed to support rapid prototyping with better data loaders, word vector loaders, neural network layer representations, common NLP metrics such as BLEU
Rosetta - Text processing tools and wrappers (e.g. Vowpal Wabbit)
PyNLPl - Python Natural Language Processing Library. General purpose NLP library for Python, handles some specific formats like ARPA language models, Moses phrasetables, GIZA++ alignments.
foliapy - Python library for working with FoLiA, an XML format for linguistic annotation.
PySS3 - Python package implementing the SS3 white-box text classifier; ships with interactive visualization tools that explain predictions.
jPTDP - A toolkit for joint part-of-speech (POS) tagging and dependency parsing. jPTDP provides pre-trained models for 40+ languages.
NLP Architect - A library for exploring the state-of-the-art deep learning topologies and techniques for NLP and NLU
Flair - A very simple framework for state-of-the-art multilingual NLP built on PyTorch. Includes BERT, ELMo and Flair embeddings.
Kashgari - Simple, Keras-powered multilingual NLP framework, allows you to build your models in 5 minutes for named entity recognition (NER), part-of-speech tagging (PoS) and text classification tasks. Includes BERT and word2vec embedding.
FARM - Fast & easy transfer learning for NLP. Harvesting language models for the industry. Focus on Question Answering.
Haystack - End-to-end Python framework for building natural language search interfaces to data. Leverages Transformers and the State-of-the-Art of NLP. Supports DPR, Elasticsearch, HuggingFace’s Modelhub, and much more!
Rita DSL - a DSL, loosely based on RUTA on Apache UIMA. Allows to define language patterns (rule-based NLP) which are then translated into spaCy, or if you prefer less features and lightweight - regex patterns.
Transformers - Natural Language Processing for TensorFlow 2.0 and PyTorch.
Tokenizers - Tokenizers optimized for Research and Production.
fairSeq Facebook AI Research implementations of SOTA seq2seq models in Pytorch.
corex_topic - Hierarchical Topic Modeling with Minimal Domain Knowledge
CRF++ - Open source implementation of Conditional Random Fields (CRFs) for segmenting/labeling sequential data & other Natural Language Processing tasks.
CRFsuite - CRFsuite is an implementation of Conditional Random Fields (CRFs) for labeling sequential data.
BLLIP Parser - BLLIP Natural Language Parser (also known as the Charniak-Johnson parser)
colibri-core - C++ library, command line tools, and Python binding for extracting and working with basic linguistic constructions such as n-grams and skipgrams in a quick and memory-efficient way.
ucto - Unicode-aware regular-expression based tokenizer for various languages. Tool and C++ library. Supports FoLiA format.
OpenRegex An efficient and flexible token-based regular expression language and engine.
CogcompNLP - Core libraries developed in the U of Illinois' Cognitive Computation Group.
MALLET - MAchine Learning for LanguagE Toolkit - package for statistical natural language processing, document classification, clustering, topic modeling, information extraction, and other machine learning applications to text.
RDRPOSTagger - A robust POS tagging toolkit available (in both Java & Python) together with pre-trained models for 40+ languages.
tm - Implementation of topic modeling based on regularized multilingual PLSA.
word2vec-scala - Scala interface to word2vec model; includes operations on vectors like word-distance and word-analogy.
Epic - Epic is a high performance statistical parser written in Scala, along with a framework for building complex structured prediction models.
Spark NLP - Spark NLP is a natural language processing library built on top of Apache Spark ML that provides simple, performant & accurate NLP annotations for machine learning pipelines that scale easily in a distributed environment.
Amazon Comprehend - NLP and ML suite covers most common tasks like NER, tagging, and sentiment analysis
Google Cloud Natural Language API - Syntax Analysis, NER, Sentiment Analysis, and Content tagging in atleast 9 languages include English and Chinese (Simplified and Traditional).
ParallelDots - High level Text Analysis API Service ranging from Sentiment Analysis to Intent Analysis
Textalytic - Natural Language Processing in the Browser with sentiment analysis, named entity extraction, POS tagging, word frequencies, topic modeling, word clouds, and more
NLP Cloud - SpaCy NLP models (custom and pre-trained ones) served through a RESTful API for named entity recognition (NER), POS tagging, and more.
Cloudmersive - Unified and free NLP APIs that perform actions such as speech tagging, text rephrasing, language translation/detection, and sentence parsing
Annotation Tools
GATE - General Architecture and Text Engineering is 15+ years old, free and open source
Anafora is free and open source, web-based raw text annotation tool
brat - brat rapid annotation tool is an online environment for collaborative text annotation
doccano - doccano is free, open-source, and provides annotation features for text classification, sequence labeling and sequence to sequence
INCEpTION - A semantic annotation platform offering intelligent assistance and knowledge management
prodigy is an annotation tool powered by active learning, costs $
LightTag - Hosted and managed text annotation tool for teams, costs $
rstWeb - open source local or online tool for discourse tree annotations
GitDox - open source server annotation tool with GitHub version control and validation for XML data and collaborative spreadsheet grids
Datasaur support various NLP tasks for individual or teams, freemium based
Konfuzio - team-first hosted and on-prem text, image and PDF annotation tool powered by active learning, freemium based, costs $
UBIAI - Easy-to-use text annotation tool for teams with most comprehensive auto-annotation features. Supports NER, relations and document classification as well as OCR annotation for invoice labeling, costs $
Shoonya - Shoonya is free and open source data annotation platform with wide varities of organization and workspace level management system. Shoonya is data agnostic, can be used by teams to annotate data with various level of verification stages at scale.
Annotation Lab - Free End-to-End No-Code platform for text annotation and DL model training/tuning. Out-of-the-box support for Named Entity Recognition, Classification, Relation extraction and Assertion Status Spark NLP models. Unlimited support for users, teams, projects, documents. Not FOSS.
FLAT - FLAT is a web-based linguistic annotation environment based around the FoLiA format, a rich XML-based format for linguistic annotation. Free and open source.
Argilla - open-source platform for collecting human feedback, building NLP and LLM datasets, and curating preference data.
Label Studio - open-core multi-modal labeling platform; widely used for NLP labeling.
NLP tasks organized by linguistic problem. Each subsection lists foundational/classical work first, then neural approaches, then LLM-based methods where relevant. For modern LM-specific research (pretraining, evaluation, retrieval, reasoning, etc.) see Language Models for NLP.
Byte Latent Transformer (BLT) (Meta, 2024) - dynamic byte-level patching that matches BPE-tokenized models at scale; revives the tokenizer-free direction.
SuperBPE (2025) - superword tokenization that improves on BPE for downstream tasks.
Over-Tokenized Transformer (ICML 2025) - decouples input and output vocabularies; shows a log-linear relationship between input vocabulary size and training loss, scaling vocabulary independently of model size.
Foundations of Tokenization (ICLR 2025) - first formal unified framework for tokenizer models using stochastic-map category theory; establishes conditions for statistical consistency.
The Token Tax: Systematic Bias in Multilingual Tokenization (2025) - quantifies how tokenization fertility predicts model accuracy across languages, exposing structural cost penalties for morphologically complex and low-resource languages.
LLMs for Semantic Role Labeling (2025) - generative LLMs with RAG and self-correction surpass encoder-decoder BERT-style models on SRL in English and Chinese.
Adapting LLMs for Minimal-edit GEC (2025) - decoder-only LLMs with a novel error-rate adaptation schedule set new SOTA on BEA-test grammatical error correction.
Gemini Embedding (2025) - Gemini-derived dense embeddings; SOTA on MMTEB across 250+ languages and on cross-lingual retrieval (XOR-Retrieve, XTREME-UP).
Qwen3-Embedding (2025) - decoder-based embedding series (0.6B-8B) built on Qwen3; #1 on MTEB Multilingual and MTEB Code, surpassing prior proprietary models.
Rank1 (2025) - first reranking model trained with test-time compute via DeepSeek-R1 reasoning-trace distillation; SOTA on instruction-following and OOD retrieval.
ReasonEmbed (2025) - embedding model for reasoning-intensive retrieval with ReMixer data synthesis and Redapter adaptive training; record nDCG@10 of 38.1 on BRIGHT.
ColBERT-Att (2026) - extends late-interaction retrieval by integrating query and document attention weights into ColBERT scoring; improves recall on MS-MARCO, BEIR, and LoTTE.
Embedding and retrieval benchmarks:
MMTEB (2025) - community expansion of MTEB to 500+ tasks across 250+ languages.
UDPipe is a trainable pipeline for tokenizing, tagging, lemmatizing and parsing Universal Treebanks and other CoNLL-U files. Primarily written in C++, offers a fast and reliable solution for multilingual NLP processing.
NLP-Cube : Natural Language Processing Pipeline - Sentence Splitting, Tokenization, Lemmatization, Part-of-speech Tagging and Dependency Parsing. New platform, written in Python with Dynet 2.0. Offers standalone (CLI/Python bindings) and server functionality (REST API).
UralicNLP is an NLP library mostly for many endangered Uralic languages such as Sami languages, Mordvin languages, Mari languages, Komi languages and so on. Also some non-endangered languages are supported such as Finnish together with non-Uralic languages such as Swedish and Arabic. UralicNLP can do morphological analysis, generation, lemmatization and disambiguation.
Pretrained language models and the research around them, scoped to NLP tasks and linguistic phenomena. For general-purpose LLM tooling, agents, or RAG application kits, see See Also.
Pretraining and Adaptation
Encoders (still the workhorse for classical NLP tasks):
BERT - bidirectional transformer pretraining; foundation for most encoder-based NLP work since 2018. Read online with section navigation and the ACL source attached.
RoBERTa - robustly optimized BERT pretraining; common encoder baseline.
ModernBERT (2024) - modernized encoder with rotary embeddings, FlashAttention, 8K context; current go-to encoder for classification, NER, retrieval.
NeoBERT (2025) - 250M-parameter encoder integrating modern architecture improvements (RoPE, 4K context, optimized depth-to-width); state of the art on MTEB, surpasses ModernBERT and RoBERTa-large under identical fine-tuning.
Encoder-decoder and seq2seq:
T5 and FLAN-T5 - text-to-text framing for NLP tasks; strong instruction-tuned encoder-decoder baselines.
BART - denoising seq2seq pretraining; widely used for summarization and generation.
Open decoder-only LMs (used as substrate for NLP tasks):
Llama 3 / 3.1 / 3.3 (Meta, 2024-2025) - widely adopted open-weight family; default base for fine-tuning across NLP tasks.
Qwen 2.5 / Qwen 3 (Alibaba, 2024-2025) - strong multilingual coverage, especially Chinese; often top open model on multilingual benchmarks.
DeepSeek-V3 (2024) - efficient MoE pretraining; competitive open base model.
SEA-LION / SeaLLM (2024-2025) - LMs targeting Southeast Asian languages.
Babel (2025) - open multilingual LLMs (9B and 83B) covering the top 25 languages by speaker population (~90% of global speakers); surpasses comparably-sized open multilingual models on XCOPA, XNLI, MGSM, FLORES-200.
Lugha-Llama (Princeton/Mila, 2025) - Llama-3.1-8B adapted for low-resource African languages via the curated WURA corpus; SOTA open-source results on IrokoBench and AfriQA.
AfriqueLLM (McGill, 2026) - suite of open LLMs (4B-14B) continued-pretrained on 26B tokens across 20 African languages with a comprehensive empirical study of data mixing.
TranslateGemma (Google, 2026) - open translation-specialized models built on Gemma 3, covering 55 language pairs via SFT and RL with quality-reward models.
MiLMMT-46 (Xiaomi, 2026) - open multilingual MT scaled across 46 languages, matching commercial systems like Google Translate and Gemini 3 Pro.
MMLU-ProX (2025) - multilingual extension of MMLU-Pro to 29 typologically diverse languages; reveals up to 24.3% performance gap between high- and low-resource languages.
MultiChallenge (2025) - multi-turn conversational benchmark exposing simultaneous instruction-following and in-context-reasoning failures; all tested frontier models score below 50%.
Kimi k1.5 (2025) - long-context RL with policy optimization (no MCTS, no PRM) reaching o1-level performance; introduces long-CoT distillation into short-CoT models.
rStar-Math (2025) - small policy model paired with a process preference model trained via MCTS rollouts; enables small LMs to bootstrap reasoning without distilling from larger models.
DAPO (2025) - open GRPO-based RL training system with four key improvements (decoupled clipping, dynamic sampling, token-level loss, entropy bonus); reproduces and surpasses DeepSeek-R1-Zero-level reasoning.
VAPO (2025) - value-model-based RL with length-adaptive GAE and token-level clipping; surpasses value-free GRPO methods on AIME 2024 with stable training.
ThinkPRM (2025) - generative process reward models that produce chain-of-thought verification per step, matching discriminative PRMs with 1% of the supervision labels.
OpenThoughts (2025) - 1000+ controlled experiments on data recipes for open reasoning models; SOTA on AIME 2025 matching closed distillation baselines.
Long Context and Alternative Architectures
Mamba and Mamba-2 - selective state-space models, linear-time long-context alternative to attention.
RWKV - RNN-transformer hybrid scaling to large parameter counts.
Titans: Learning to Memorize at Test Time (2025) - neural long-term memory module that learns to memorize historical context at test time; scales beyond 2M tokens, outperforms transformers and modern linear-recurrent models on language modeling and reasoning.
MiniMax-01 (2025) - 456B-parameter hybrid combining lightning (linear) attention with sparse softmax attention; matches GPT-4o-level NLP performance at up to 4M-token inference contexts.
Native Sparse Attention (NSA) (2025) - trainable sparse attention combining coarse-grained compression with fine-grained selection; large speedups at 64K with no NLP-benchmark degradation.
LongRoPE2 (2025) - identifies undertraining of high-frequency RoPE dimensions and applies evolutionary-search rescaling; extends LLaMA3-8B to 128K with 80x fewer training tokens than Meta's recipe.
Characterizing SSM and Hybrid LM Long-Context Performance (2025) - first comprehensive memory and speed analysis of transformer, SSM, and hybrid models up to 220K tokens; SSMs are up to 4x faster, hybrids balance recall and efficiency.
HalluLens (2025) - hallucination benchmark with extrinsic/intrinsic taxonomy and dynamic test-set regeneration to resist data leakage.
Atomic Calibration (2025) - claim-level calibration analysis for long-form generation; models are substantially worse-calibrated on extended outputs than on single claims.
FRANQ (2025) - faithfulness-aware uncertainty quantification for RAG fact-checking; formally separates faithfulness from factuality.
MUCH (2025) - multilingual claim-hallucination benchmark across English, French, Spanish, German with token-level logits released for principled UQ evaluation.
HalluHard (2026) - hard multi-turn hallucination benchmark for citation-required responses; ~30% hallucination rates persist even with web search.
CURE: Think Through Uncertainty (2026) - trains models to reason about claim-level uncertainty before generating; large gains on biography factuality and FactBench AUROC.
Circuit Tracing: Revealing Computational Graphs in Language Models (Anthropic, 2025) - introduces cross-layer transcoders and attribution graphs to construct an interpretable replacement model; enables prompt-level circuit tracing of feature-to-feature causal interactions.
On the Biology of a Large Language Model (Anthropic, 2025) - applies attribution graphs to Claude 3.5 Haiku across multi-hop reasoning, rhyme planning, and jailbreak case studies.
Tülu 3 (AI2, 2024) - fully open post-training recipe with state-of-the-art results among open models.
LIMA - "less is more for alignment"; small high-quality SFT data goes a long way.
TRL - reference library for SFT, DPO, GRPO, and RLHF.
Magpie (2024-2025) - synthesizes high-quality instruction-response pairs by prompting aligned LMs with nothing; SFT on the filtered subset matches official Llama-3-Instruct.
Bias, Fairness, Safety in NLP
StereoSet - measuring stereotypical bias in pretrained LMs.
CrowS-Pairs - social bias measurement in masked LMs.
WildGuard (2024) - open safety moderation model and benchmark.
Emergent Misalignment (2025) - finetuning on a narrow task (insecure code) unexpectedly produces broad alignment failures across unrelated domains.
SafeDialBench (2025) - multilingual (Chinese/English) safety benchmark of 4000+ multi-turn dialogues across 22 scenarios and 7 jailbreak strategies.
TeleAI-Safety (2025) - modular jailbreak evaluation framework integrating 19 attacks, 29 defenses, and 19 evaluation methods across 14 models and 12 risk categories.
IndicSafe (2026) - multilingual safety benchmark across 12 Indic languages; reveals 12.8% cross-language agreement, with over-refusal in low-resource scripts.
VLAF: Value-Conflict Alignment Faking (2026) - alignment faking occurs in models as small as 7B in 37% of cases when policy conflicts with internalized values; steering-vector mitigation reduces it 94%.
EVB Corpus - 20M words across 15 bilingual books, 100 parallel English-Vietnamese texts, 250 parallel law texts, 5K news articles, and 2K film subtitles.
Other Languages
Russian: pymorphy2 - a good pos-tagger for Russian
Asian Languages: Thai, Lao, Chinese, Japanese, and Korean ICU Tokenizer implementation in ElasticSearch
Ancient Languages: CLTK: The Classical Language Toolkit is a Python library and collection of texts for doing NLP in ancient languages
Hebrew: NLPH_Resources - A collection of papers, corpora and linguistic resources for NLP in Hebrew
AI API aggregation platform with an OpenAI-compatible LLM endpoint for NLP tasks such as translation, summarization, multilingual generation, and structured extraction.
A curated list of resources dedicated to Natural Language Processing
This list covers natural language processing — linguistic analysis, multilingual tooling, classical and neural methods, datasets, and evaluation. Large language models are included only where they advance or evaluate a core NLP task or capability (tokenization, multilinguality, MT, summarization, NER, QA, factuality, probing, distillation). General-purpose chatbots, agent frameworks, prompt-template repositories, code-generation tools, and RAG application starter kits live in other lists — see See Also.
The Berkeley NLP Group - Notable contributions include a tool to reconstruct long dead languages, referenced here and by taking corpora from 637 languages currently spoken in Asia and the Pacific and recreating their descendant.
NLP research group, Columbia University - Responsible for creating BOLT ( interactive error handling for speech translation systems) and an un-named project to characterize laughter in dialogue.
Advanced NLP with spaCy - Free online course covering text processing, large-scale data analysis, processing pipelines, and training neural network models for custom NLP tasks.
Kaggle NLP Learning Guide - Beginner-friendly tutorials including getting started guides, deep learning for NLP, and visual explanations of techniques like BERT, GloVe, and TF-IDF.
Deep NLP Course by Yandex Data School, covering important ideas from text embedding to machine translation including sequence modeling, language models and so on.
fast.ai Code-First Intro to Natural Language Processing - This covers a blend of traditional NLP topics (including regex, SVD, naive bayes, tokenization) and recent neural network approaches (including RNNs, seq2seq, GRUs, and the Transformer), as well as addressing urgent ethical issues, such as bias and disinformation. Find the Jupyter Notebooks here
Applied Natural Language Processing- Lecture series from IIT Madras taking from the basics all the way to autoencoders and everything. The github notebooks for this course are also available here
DeepLearning.AI Natural Language Processing Specialization - 4-course program covering sentiment analysis, word embeddings, RNNs, LSTMs, attention mechanisms, and Transformer models like BERT and T5 for tasks including machine translation and summarization.
The Math Behind Artificial Intelligence - bt Tiago MOnteiro | A free FreeCodeCamp book teaching the math behind AI in plain English from an engineering point of view. It covers linear algebra, calculus, probability & statistics, and optimization theory with analogies, real-life applications, and Python code examples.
TextAttack - Adversarial attacks, adversarial training, and data augmentation in NLP
TextBlob - Providing a consistent API for diving into common natural language processing (NLP) tasks. Stands on the giant shoulders of Natural Language Toolkit (NLTK) and Pattern, and plays nicely with both :+1:
spaCy - Industrial strength NLP with Python and Cython :+1:
gensim - Python library to conduct unsupervised semantic modelling from plain text :+1:
scattertext - Python library to produce d3 visualizations of how language differs between corpora
GluonNLP(archived) - A deep learning toolkit for NLP, built on MXNet/Gluon.
AllenNLP(archived) - An NLP research library, built on PyTorch, for developing state-of-the-art deep learning models on a wide variety of linguistic tasks.
PyTorch-NLP - NLP research toolkit designed to support rapid prototyping with better data loaders, word vector loaders, neural network layer representations, common NLP metrics such as BLEU
Rosetta - Text processing tools and wrappers (e.g. Vowpal Wabbit)
PyNLPl - Python Natural Language Processing Library. General purpose NLP library for Python, handles some specific formats like ARPA language models, Moses phrasetables, GIZA++ alignments.
foliapy - Python library for working with FoLiA, an XML format for linguistic annotation.
PySS3 - Python package implementing the SS3 white-box text classifier; ships with interactive visualization tools that explain predictions.
jPTDP - A toolkit for joint part-of-speech (POS) tagging and dependency parsing. jPTDP provides pre-trained models for 40+ languages.
NLP Architect - A library for exploring the state-of-the-art deep learning topologies and techniques for NLP and NLU
Flair - A very simple framework for state-of-the-art multilingual NLP built on PyTorch. Includes BERT, ELMo and Flair embeddings.
Kashgari - Simple, Keras-powered multilingual NLP framework, allows you to build your models in 5 minutes for named entity recognition (NER), part-of-speech tagging (PoS) and text classification tasks. Includes BERT and word2vec embedding.
FARM - Fast & easy transfer learning for NLP. Harvesting language models for the industry. Focus on Question Answering.
Haystack - End-to-end Python framework for building natural language search interfaces to data. Leverages Transformers and the State-of-the-Art of NLP. Supports DPR, Elasticsearch, HuggingFace’s Modelhub, and much more!
Rita DSL - a DSL, loosely based on RUTA on Apache UIMA. Allows to define language patterns (rule-based NLP) which are then translated into spaCy, or if you prefer less features and lightweight - regex patterns.
Transformers - Natural Language Processing for TensorFlow 2.0 and PyTorch.
Tokenizers - Tokenizers optimized for Research and Production.
fairSeq Facebook AI Research implementations of SOTA seq2seq models in Pytorch.
corex_topic - Hierarchical Topic Modeling with Minimal Domain Knowledge
CRF++ - Open source implementation of Conditional Random Fields (CRFs) for segmenting/labeling sequential data & other Natural Language Processing tasks.
CRFsuite - CRFsuite is an implementation of Conditional Random Fields (CRFs) for labeling sequential data.
BLLIP Parser - BLLIP Natural Language Parser (also known as the Charniak-Johnson parser)
colibri-core - C++ library, command line tools, and Python binding for extracting and working with basic linguistic constructions such as n-grams and skipgrams in a quick and memory-efficient way.
ucto - Unicode-aware regular-expression based tokenizer for various languages. Tool and C++ library. Supports FoLiA format.
OpenRegex An efficient and flexible token-based regular expression language and engine.
CogcompNLP - Core libraries developed in the U of Illinois' Cognitive Computation Group.
MALLET - MAchine Learning for LanguagE Toolkit - package for statistical natural language processing, document classification, clustering, topic modeling, information extraction, and other machine learning applications to text.
RDRPOSTagger - A robust POS tagging toolkit available (in both Java & Python) together with pre-trained models for 40+ languages.
tm - Implementation of topic modeling based on regularized multilingual PLSA.
word2vec-scala - Scala interface to word2vec model; includes operations on vectors like word-distance and word-analogy.
Epic - Epic is a high performance statistical parser written in Scala, along with a framework for building complex structured prediction models.
Spark NLP - Spark NLP is a natural language processing library built on top of Apache Spark ML that provides simple, performant & accurate NLP annotations for machine learning pipelines that scale easily in a distributed environment.
Amazon Comprehend - NLP and ML suite covers most common tasks like NER, tagging, and sentiment analysis
Google Cloud Natural Language API - Syntax Analysis, NER, Sentiment Analysis, and Content tagging in atleast 9 languages include English and Chinese (Simplified and Traditional).
ParallelDots - High level Text Analysis API Service ranging from Sentiment Analysis to Intent Analysis
Textalytic - Natural Language Processing in the Browser with sentiment analysis, named entity extraction, POS tagging, word frequencies, topic modeling, word clouds, and more
NLP Cloud - SpaCy NLP models (custom and pre-trained ones) served through a RESTful API for named entity recognition (NER), POS tagging, and more.
Cloudmersive - Unified and free NLP APIs that perform actions such as speech tagging, text rephrasing, language translation/detection, and sentence parsing
Annotation Tools
GATE - General Architecture and Text Engineering is 15+ years old, free and open source
Anafora is free and open source, web-based raw text annotation tool
brat - brat rapid annotation tool is an online environment for collaborative text annotation
doccano - doccano is free, open-source, and provides annotation features for text classification, sequence labeling and sequence to sequence
INCEpTION - A semantic annotation platform offering intelligent assistance and knowledge management
prodigy is an annotation tool powered by active learning, costs $
LightTag - Hosted and managed text annotation tool for teams, costs $
rstWeb - open source local or online tool for discourse tree annotations
GitDox - open source server annotation tool with GitHub version control and validation for XML data and collaborative spreadsheet grids
Datasaur support various NLP tasks for individual or teams, freemium based
Konfuzio - team-first hosted and on-prem text, image and PDF annotation tool powered by active learning, freemium based, costs $
UBIAI - Easy-to-use text annotation tool for teams with most comprehensive auto-annotation features. Supports NER, relations and document classification as well as OCR annotation for invoice labeling, costs $
Shoonya - Shoonya is free and open source data annotation platform with wide varities of organization and workspace level management system. Shoonya is data agnostic, can be used by teams to annotate data with various level of verification stages at scale.
Annotation Lab - Free End-to-End No-Code platform for text annotation and DL model training/tuning. Out-of-the-box support for Named Entity Recognition, Classification, Relation extraction and Assertion Status Spark NLP models. Unlimited support for users, teams, projects, documents. Not FOSS.
FLAT - FLAT is a web-based linguistic annotation environment based around the FoLiA format, a rich XML-based format for linguistic annotation. Free and open source.
Argilla - open-source platform for collecting human feedback, building NLP and LLM datasets, and curating preference data.
Label Studio - open-core multi-modal labeling platform; widely used for NLP labeling.
NLP tasks organized by linguistic problem. Each subsection lists foundational/classical work first, then neural approaches, then LLM-based methods where relevant. For modern LM-specific research (pretraining, evaluation, retrieval, reasoning, etc.) see Language Models for NLP.
Byte Latent Transformer (BLT) (Meta, 2024) - dynamic byte-level patching that matches BPE-tokenized models at scale; revives the tokenizer-free direction.
SuperBPE (2025) - superword tokenization that improves on BPE for downstream tasks.
Over-Tokenized Transformer (ICML 2025) - decouples input and output vocabularies; shows a log-linear relationship between input vocabulary size and training loss, scaling vocabulary independently of model size.
Foundations of Tokenization (ICLR 2025) - first formal unified framework for tokenizer models using stochastic-map category theory; establishes conditions for statistical consistency.
The Token Tax: Systematic Bias in Multilingual Tokenization (2025) - quantifies how tokenization fertility predicts model accuracy across languages, exposing structural cost penalties for morphologically complex and low-resource languages.
LLMs for Semantic Role Labeling (2025) - generative LLMs with RAG and self-correction surpass encoder-decoder BERT-style models on SRL in English and Chinese.
Adapting LLMs for Minimal-edit GEC (2025) - decoder-only LLMs with a novel error-rate adaptation schedule set new SOTA on BEA-test grammatical error correction.
Gemini Embedding (2025) - Gemini-derived dense embeddings; SOTA on MMTEB across 250+ languages and on cross-lingual retrieval (XOR-Retrieve, XTREME-UP).
Qwen3-Embedding (2025) - decoder-based embedding series (0.6B-8B) built on Qwen3; #1 on MTEB Multilingual and MTEB Code, surpassing prior proprietary models.
Rank1 (2025) - first reranking model trained with test-time compute via DeepSeek-R1 reasoning-trace distillation; SOTA on instruction-following and OOD retrieval.
ReasonEmbed (2025) - embedding model for reasoning-intensive retrieval with ReMixer data synthesis and Redapter adaptive training; record nDCG@10 of 38.1 on BRIGHT.
ColBERT-Att (2026) - extends late-interaction retrieval by integrating query and document attention weights into ColBERT scoring; improves recall on MS-MARCO, BEIR, and LoTTE.
Embedding and retrieval benchmarks:
MMTEB (2025) - community expansion of MTEB to 500+ tasks across 250+ languages.
UDPipe is a trainable pipeline for tokenizing, tagging, lemmatizing and parsing Universal Treebanks and other CoNLL-U files. Primarily written in C++, offers a fast and reliable solution for multilingual NLP processing.
NLP-Cube : Natural Language Processing Pipeline - Sentence Splitting, Tokenization, Lemmatization, Part-of-speech Tagging and Dependency Parsing. New platform, written in Python with Dynet 2.0. Offers standalone (CLI/Python bindings) and server functionality (REST API).
UralicNLP is an NLP library mostly for many endangered Uralic languages such as Sami languages, Mordvin languages, Mari languages, Komi languages and so on. Also some non-endangered languages are supported such as Finnish together with non-Uralic languages such as Swedish and Arabic. UralicNLP can do morphological analysis, generation, lemmatization and disambiguation.
Pretrained language models and the research around them, scoped to NLP tasks and linguistic phenomena. For general-purpose LLM tooling, agents, or RAG application kits, see See Also.
Pretraining and Adaptation
Encoders (still the workhorse for classical NLP tasks):
BERT - bidirectional transformer pretraining; foundation for most encoder-based NLP work since 2018. Read online with section navigation and the ACL source attached.
RoBERTa - robustly optimized BERT pretraining; common encoder baseline.
ModernBERT (2024) - modernized encoder with rotary embeddings, FlashAttention, 8K context; current go-to encoder for classification, NER, retrieval.
NeoBERT (2025) - 250M-parameter encoder integrating modern architecture improvements (RoPE, 4K context, optimized depth-to-width); state of the art on MTEB, surpasses ModernBERT and RoBERTa-large under identical fine-tuning.
Encoder-decoder and seq2seq:
T5 and FLAN-T5 - text-to-text framing for NLP tasks; strong instruction-tuned encoder-decoder baselines.
BART - denoising seq2seq pretraining; widely used for summarization and generation.
Open decoder-only LMs (used as substrate for NLP tasks):
Llama 3 / 3.1 / 3.3 (Meta, 2024-2025) - widely adopted open-weight family; default base for fine-tuning across NLP tasks.
Qwen 2.5 / Qwen 3 (Alibaba, 2024-2025) - strong multilingual coverage, especially Chinese; often top open model on multilingual benchmarks.
DeepSeek-V3 (2024) - efficient MoE pretraining; competitive open base model.
SEA-LION / SeaLLM (2024-2025) - LMs targeting Southeast Asian languages.
Babel (2025) - open multilingual LLMs (9B and 83B) covering the top 25 languages by speaker population (~90% of global speakers); surpasses comparably-sized open multilingual models on XCOPA, XNLI, MGSM, FLORES-200.
Lugha-Llama (Princeton/Mila, 2025) - Llama-3.1-8B adapted for low-resource African languages via the curated WURA corpus; SOTA open-source results on IrokoBench and AfriQA.
AfriqueLLM (McGill, 2026) - suite of open LLMs (4B-14B) continued-pretrained on 26B tokens across 20 African languages with a comprehensive empirical study of data mixing.
TranslateGemma (Google, 2026) - open translation-specialized models built on Gemma 3, covering 55 language pairs via SFT and RL with quality-reward models.
MiLMMT-46 (Xiaomi, 2026) - open multilingual MT scaled across 46 languages, matching commercial systems like Google Translate and Gemini 3 Pro.
MMLU-ProX (2025) - multilingual extension of MMLU-Pro to 29 typologically diverse languages; reveals up to 24.3% performance gap between high- and low-resource languages.
MultiChallenge (2025) - multi-turn conversational benchmark exposing simultaneous instruction-following and in-context-reasoning failures; all tested frontier models score below 50%.
Kimi k1.5 (2025) - long-context RL with policy optimization (no MCTS, no PRM) reaching o1-level performance; introduces long-CoT distillation into short-CoT models.
rStar-Math (2025) - small policy model paired with a process preference model trained via MCTS rollouts; enables small LMs to bootstrap reasoning without distilling from larger models.
DAPO (2025) - open GRPO-based RL training system with four key improvements (decoupled clipping, dynamic sampling, token-level loss, entropy bonus); reproduces and surpasses DeepSeek-R1-Zero-level reasoning.
VAPO (2025) - value-model-based RL with length-adaptive GAE and token-level clipping; surpasses value-free GRPO methods on AIME 2024 with stable training.
ThinkPRM (2025) - generative process reward models that produce chain-of-thought verification per step, matching discriminative PRMs with 1% of the supervision labels.
OpenThoughts (2025) - 1000+ controlled experiments on data recipes for open reasoning models; SOTA on AIME 2025 matching closed distillation baselines.
Long Context and Alternative Architectures
Mamba and Mamba-2 - selective state-space models, linear-time long-context alternative to attention.
RWKV - RNN-transformer hybrid scaling to large parameter counts.
Titans: Learning to Memorize at Test Time (2025) - neural long-term memory module that learns to memorize historical context at test time; scales beyond 2M tokens, outperforms transformers and modern linear-recurrent models on language modeling and reasoning.
MiniMax-01 (2025) - 456B-parameter hybrid combining lightning (linear) attention with sparse softmax attention; matches GPT-4o-level NLP performance at up to 4M-token inference contexts.
Native Sparse Attention (NSA) (2025) - trainable sparse attention combining coarse-grained compression with fine-grained selection; large speedups at 64K with no NLP-benchmark degradation.
LongRoPE2 (2025) - identifies undertraining of high-frequency RoPE dimensions and applies evolutionary-search rescaling; extends LLaMA3-8B to 128K with 80x fewer training tokens than Meta's recipe.
Characterizing SSM and Hybrid LM Long-Context Performance (2025) - first comprehensive memory and speed analysis of transformer, SSM, and hybrid models up to 220K tokens; SSMs are up to 4x faster, hybrids balance recall and efficiency.
HalluLens (2025) - hallucination benchmark with extrinsic/intrinsic taxonomy and dynamic test-set regeneration to resist data leakage.
Atomic Calibration (2025) - claim-level calibration analysis for long-form generation; models are substantially worse-calibrated on extended outputs than on single claims.
FRANQ (2025) - faithfulness-aware uncertainty quantification for RAG fact-checking; formally separates faithfulness from factuality.
MUCH (2025) - multilingual claim-hallucination benchmark across English, French, Spanish, German with token-level logits released for principled UQ evaluation.
HalluHard (2026) - hard multi-turn hallucination benchmark for citation-required responses; ~30% hallucination rates persist even with web search.
CURE: Think Through Uncertainty (2026) - trains models to reason about claim-level uncertainty before generating; large gains on biography factuality and FactBench AUROC.
Circuit Tracing: Revealing Computational Graphs in Language Models (Anthropic, 2025) - introduces cross-layer transcoders and attribution graphs to construct an interpretable replacement model; enables prompt-level circuit tracing of feature-to-feature causal interactions.
On the Biology of a Large Language Model (Anthropic, 2025) - applies attribution graphs to Claude 3.5 Haiku across multi-hop reasoning, rhyme planning, and jailbreak case studies.
Tülu 3 (AI2, 2024) - fully open post-training recipe with state-of-the-art results among open models.
LIMA - "less is more for alignment"; small high-quality SFT data goes a long way.
TRL - reference library for SFT, DPO, GRPO, and RLHF.
Magpie (2024-2025) - synthesizes high-quality instruction-response pairs by prompting aligned LMs with nothing; SFT on the filtered subset matches official Llama-3-Instruct.
Bias, Fairness, Safety in NLP
StereoSet - measuring stereotypical bias in pretrained LMs.
CrowS-Pairs - social bias measurement in masked LMs.
WildGuard (2024) - open safety moderation model and benchmark.
Emergent Misalignment (2025) - finetuning on a narrow task (insecure code) unexpectedly produces broad alignment failures across unrelated domains.
SafeDialBench (2025) - multilingual (Chinese/English) safety benchmark of 4000+ multi-turn dialogues across 22 scenarios and 7 jailbreak strategies.
TeleAI-Safety (2025) - modular jailbreak evaluation framework integrating 19 attacks, 29 defenses, and 19 evaluation methods across 14 models and 12 risk categories.
IndicSafe (2026) - multilingual safety benchmark across 12 Indic languages; reveals 12.8% cross-language agreement, with over-refusal in low-resource scripts.
VLAF: Value-Conflict Alignment Faking (2026) - alignment faking occurs in models as small as 7B in 37% of cases when policy conflicts with internalized values; steering-vector mitigation reduces it 94%.
EVB Corpus - 20M words across 15 bilingual books, 100 parallel English-Vietnamese texts, 250 parallel law texts, 5K news articles, and 2K film subtitles.
Other Languages
Russian: pymorphy2 - a good pos-tagger for Russian
Asian Languages: Thai, Lao, Chinese, Japanese, and Korean ICU Tokenizer implementation in ElasticSearch
Ancient Languages: CLTK: The Classical Language Toolkit is a Python library and collection of texts for doing NLP in ancient languages
Hebrew: NLPH_Resources - A collection of papers, corpora and linguistic resources for NLP in Hebrew