Install Lasso in your app

Lasso is standard EVM JSON-RPC, so installing it means changing one URL. Your client library, contract calls and secret store stay as they are. This page shows the URL in each common client and how to move traffic over safely.

# .env
LASSO_RPC_URL=https://lasso.sh/rpc/k/lasso_…/profile/premium
LASSO_WS_URL=wss://lasso.sh/ws/rpc/k/lasso_…/profile/premium

Get these values from the quickstart. Every URL below is built from them as <base>[/profile/<profile>][/<strategy>]/<chain>; see keys, URLs and profiles.

viem

import { createPublicClient, http, webSocket } from "viem";
import { base } from "viem/chains";

const client = createPublicClient({
  chain: base,
  transport: http(`${process.env.LASSO_RPC_URL}/balanced-fast/base`),
});

const subscriber = createPublicClient({
  chain: base,
  transport: webSocket(`${process.env.LASSO_WS_URL}/base`),
});

ethers v6

import { JsonRpcProvider, WebSocketProvider } from "ethers";

const provider = new JsonRpcProvider(
  `${process.env.LASSO_RPC_URL}/balanced-fast/base`,
  8453,
  { staticNetwork: true, polling: true },
);

const subscriber = new WebSocketProvider(`${process.env.LASSO_WS_URL}/base`, 8453);

polling: true makes provider.on(...) poll with eth_getLogs instead of HTTP filters, which Lasso doesn’t serve. For push delivery, use the WebSocket provider.

Foundry, Hardhat and indexers

cast block-number --rpc-url "$LASSO_RPC_URL/base"
forge script Deploy --rpc-url "$LASSO_RPC_URL/fastest/base" --broadcast

// hardhat.config.ts
networks: {
  base: { url: `${process.env.LASSO_RPC_URL}/fastest/base` },
},

Indexers take the same URL wherever they take an RPC endpoint. Use load-balanced for backfills; see indexer backfills.

Choose the URL per call site

Call site	URL
User-facing reads	`$LASSO_RPC_URL/balanced-fast/<chain>`
Trading, quoting, liquidations	`$LASSO_RPC_URL/fastest/<chain>`
Backfills and batch jobs	`$LASSO_RPC_URL/load-balanced/<chain>`
Development, tests and work that doesn’t need premium	`https://lasso.sh/rpc/k/<key>/profile/public/<chain>`
Your own providers	`https://lasso.sh/rpc/k/<key>/profile/<slug>/<strategy>/<chain>`
Subscriptions	`$LASSO_WS_URL/<chain>`

Roll out one path at a time

Pick one stateless read path your app already measures, such as a balance or eth_blockNumber poller.
Point it at Lasso with an explicit strategy, and keep the previous URL as a rollback.
Compare correctness, error rate, latency and head freshness against the old endpoint, and check routing evidence to see which provider served each request.
Move historical reads, transaction sending and subscriptions as separate steps; each has its own behavior in RPC method behavior.
Expand traffic once your own evidence supports it.

Limits

Lasso rejects HTTP filter methods (eth_newFilter and friends). Use eth_getLogs or WebSocket subscriptions.
JSON-RPC batches are routed per item, so one batch can span providers and blocks. For reads at one block, use read at one block.

Keys, URLs and profiles: the URL grammar and scoped keys.
Routing: what each strategy does, and how to trial it against your current endpoint.

Get started

Concepts

Guides

Reference

Updates

Install Lasso in your app

Install Lasso in your app

viem

ethers v6

Foundry, Hardhat and indexers

Choose the URL per call site

Roll out one path at a time

Limits

Next

​Install Lasso in your app

​viem

​ethers v6

​Foundry, Hardhat and indexers

​Choose the URL per call site

​Roll out one path at a time

​Limits

​Next

Install Lasso in your app

viem

ethers v6

Foundry, Hardhat and indexers

Choose the URL per call site

Roll out one path at a time

Limits

Next