Subxt is a library for interacting with chains in the Polkadot network. It can:

• Submit Extrinsics (this is where the name comes from).
• Access information at any block (eg storage values, constants, Runtime APIs, View Functions).
• Subscribe to new blocks (and then do the above at them).
• Do all of the above via a safe, statically typed interface or via a flexible dynamic interface.
• Do most of the above via a built-in light client to interact with chains trustlessly.
• Compile to WASM and run entirely in the browser, or be called via FFI in many other languages.
• Be used entirely offline to provide a subset of the available functionality.

Usage

Take a look at the single-file examples folder or the project based examples folder for various smaller or larger subxt usage examples, or read the docs to learn more.

Example

The "hello world" example of Subxt is submitting a transaction. This is what it looks like:

use subxt::{Error, OnlineClient, PolkadotConfig};
use subxt_signer::sr25519::dev;

// Generate an interface that we can use from the node's metadata.
#[subxt::subxt(runtime_metadata_path = "/path/to/polkadot_rc_metadata.scale")]
mod polkadot {}

#[tokio::main]
async fn main() -> Result<(), Error> {
    // Create a new API client, configured to talk to Polkadot nodes.
    let api = OnlineClient::<PolkadotConfig>::new().await?;

    // Almost all actions are performed at an explicit block. Here we use
    // the current block at the time of running this.
    let at_block = api.at_current_block().await?;

    // Build a balance transfer extrinsic.
    let dest = dev::bob().public_key().into();
    let balance_transfer_tx = polkadot::transactions()
        .balances()
        .transfer_allow_death(dest, 10_000);

    // Submit the balance transfer extrinsic from Alice, and wait for it 
    // to be successful and in a finalized block. We get back the extrinsic 
    // events if all is well.
    let from = dev::alice();
    let events = at_block
        .transactions()
        .sign_and_submit_then_watch_default(&balance_transfer_tx, &from)
        .await?
        .wait_for_finalized_success()
        .await?;

    // (Optional) we can look for a specific event to learn more about 
    // the submission.
    if let Some(event) = events.find_first::<polkadot::balances::events::Transfer>() {
        println!("Balance transfer success: {event:?}");
    }

    Ok(())
}

Real world usage

Please add your project to this list via a PR.

• cargo-contract CLI for interacting with Wasm smart contracts.
• xcm-cli CLI for submitting XCM messages.
• phala-pherry The relayer between Phala blockchain and the off-chain Secure workers.
• crunch CLI to claim staking rewards in batch every Era or X hours for substrate-based chains.
• interbtc-clients Client implementations for the interBTC parachain; notably the Vault / Relayer and Oracle.
• tidext Tidechain client with Stronghold signer.
• staking-miner-v2 Submit NPos election solutions and get rewards.
• polkadot-introspector Tools for monitoring Polkadot nodes.
• ink! Smart contract language that uses subxt for allowing developers to conduct End-to-End testing of their contracts.
• Chainflip A decentralised exchange for native cross-chain swaps.
• Hyperbridge A hyperscalable coprocessor for verifiable cross-chain interoperability.
• pop CLI The all-in-one tool for Polkadot development.

Alternatives

If you're working in TypeScript / JavaScript, polkadot-api is an excellent and actively developed alternative.

License

The entire code within this repository is dual licensed under the GPL-3.0 or Apache-2.0 licenses. See the LICENSE file for more details.

Please contact us if you have questions about the licensing of our products.