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timgioh/PromptLab-Local-First-LLM-Prompt-Testing-in-Your-Browser

A lightweight, local-first Chrome sidepanel extension to test and evaluate LLM prompt fixtures across OpenAI, Anthropic, and OpenRouter. Features direct browser-to-API requests, real-time token tracking, zero telemetry, and pure BYOK (Bring Your Own Key) privacy. Built with React, TypeScript, and Vite.

2

stars

1

commits

TypeScript

primary language

Sep 1, 2026

updated

README

PromptLab

Chrome extension (Manifest V3) for managing local prompt fixtures. Nothing leaves the machine: no analytics, no remote APIs, no cloud storage.

Stack

  • React + TypeScript + Vite
  • Tailwind CSS
  • @crxjs/vite-plugin for the extension build
  • chrome.storage.local in the extension, localStorage in the browser preview

Quick demo (browser)

npm install
npm run dev

Opens a local dashboard at http://localhost:5173. Add, edit, and delete up to 20 prompt fixtures. Run Eval is a stub for tomorrow’s LLM wiring.

Load as an unpacked extension

npm run build

Then in Chrome:

  1. Open chrome://extensions
  2. Enable Developer mode
  3. Click Load unpacked
  4. Select the dist folder

Click the extension icon to open the side panel.

For live reload while developing the extension:

npm run dev:extension

Load the generated dist folder as unpacked. Keep the Vite process running.

Privacy

  • Fixtures persist only in chrome.storage.local (or localStorage in the web preview)
  • No telemetry, fonts-from-CDN, or outbound requests in this app
  • Permissions: storage, activeTab, and sidePanel (needed to host the dashboard)

Contributors

timgioh

1 commits

See what people are saying

Hacker News (1)

Show HN: PromptLab – Local-first Chrome sidepanel for LLM prompt testing

1 points · Sep 1, 2026

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timgioh/PromptLab-Local-First-LLM-Prompt-Testing-in-Your-Browser

A lightweight, local-first Chrome sidepanel extension to test and evaluate LLM prompt fixtures across OpenAI, Anthropic, and OpenRouter. Features direct browser-to-API requests, real-time token tracking, zero telemetry, and pure BYOK (Bring Your Own Key) privacy. Built with React, TypeScript, and Vite.

2

stars

1

commits

TypeScript

primary language

Sep 1, 2026

updated

README

PromptLab

Chrome extension (Manifest V3) for managing local prompt fixtures. Nothing leaves the machine: no analytics, no remote APIs, no cloud storage.

Stack

  • React + TypeScript + Vite
  • Tailwind CSS
  • @crxjs/vite-plugin for the extension build
  • chrome.storage.local in the extension, localStorage in the browser preview

Quick demo (browser)

npm install
npm run dev

Opens a local dashboard at http://localhost:5173. Add, edit, and delete up to 20 prompt fixtures. Run Eval is a stub for tomorrow’s LLM wiring.

Load as an unpacked extension

npm run build

Then in Chrome:

  1. Open chrome://extensions
  2. Enable Developer mode
  3. Click Load unpacked
  4. Select the dist folder

Click the extension icon to open the side panel.

For live reload while developing the extension:

npm run dev:extension

Load the generated dist folder as unpacked. Keep the Vite process running.

Privacy

  • Fixtures persist only in chrome.storage.local (or localStorage in the web preview)
  • No telemetry, fonts-from-CDN, or outbound requests in this app
  • Permissions: storage, activeTab, and sidePanel (needed to host the dashboard)

See what people are saying

Hacker News (1)

Show HN: PromptLab – Local-first Chrome sidepanel for LLM prompt testing

1 points · Sep 1, 2026

Similar repos

n4ze3m/page-assist

Use your locally running AI models to assist you in your web browsing

8,205

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Contributors

timgioh

1 commits

Languages

TypeScript

98.6%