> ## Documentation Index > Fetch the complete documentation index at: https://docs.lasso.sh/llms.txt > Use this file to discover all available pages before exploring further. # HTTP Endpoints > Complete reference for Lasso RPC HTTP JSON-RPC endpoints ## Overview All HTTP RPC endpoints accept `POST` requests with `Content-Type: application/json` and follow the JSON-RPC 2.0 specification. ## Base Endpoint Routes requests using the default strategy (configurable, defaults to `load_balanced`). ``` POST /rpc/:chain ``` ### Parameters * `:chain` - Chain identifier (name or numeric ID) * **Chain name**: `ethereum`, `base`, `arbitrum` * **Chain ID**: `1`, `8453`, `42161` ### Example ```bash theme={null} curl -X POST http://localhost:4000/rpc/ethereum \ -H 'Content-Type: application/json' \ -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}' ``` **Response:** ```json theme={null} { "jsonrpc": "2.0", "id": 1, "result": "0x8471c9a" } ``` ## Strategy Endpoints Explicitly specify the routing strategy for provider selection. ### Fastest ``` POST /rpc/fastest/:chain ``` Routes all requests to the single fastest provider based on measured latency. ```bash theme={null} curl -X POST http://localhost:4000/rpc/fastest/ethereum \ -H 'Content-Type: application/json' \ -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}' ``` ### Load Balanced ``` POST /rpc/load-balanced/:chain POST /rpc/round-robin/:chain ``` Randomly distributes requests across healthy providers. ```bash theme={null} curl -X POST http://localhost:4000/rpc/load-balanced/ethereum \ -H 'Content-Type: application/json' \ -d '{"jsonrpc":"2.0","method":"eth_getBalance","params":["0x123...","latest"],"id":1}' ``` ### Latency Weighted ``` POST /rpc/latency-weighted/:chain ``` Probabilistically routes requests with bias toward lower-latency providers. ```bash theme={null} curl -X POST http://localhost:4000/rpc/latency-weighted/ethereum \ -H 'Content-Type: application/json' \ -d '{"jsonrpc":"2.0","method":"eth_call","params":[{"to":"0x...","data":"0x..."},"latest"],"id":1}' ``` ## Provider Override Endpoints Route directly to a specific provider, bypassing strategy selection. ``` POST /rpc/provider/:provider_id/:chain POST /rpc/:chain/:provider_id ``` ### Parameters * `:provider_id` - Provider identifier (e.g., `alchemy`, `infura`, `quicknode`) * `:chain` - Chain identifier ### Example ```bash theme={null} curl -X POST http://localhost:4000/rpc/provider/alchemy/ethereum \ -H 'Content-Type: application/json' \ -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}' ``` Alternative syntax: ```bash theme={null} curl -X POST http://localhost:4000/rpc/ethereum/alchemy \ -H 'Content-Type: application/json' \ -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}' ``` ## Profile-Scoped Endpoints All routes above are available under a profile namespace for multi-tenancy. ``` POST /rpc/profile/:profile/:chain POST /rpc/profile/:profile/fastest/:chain POST /rpc/profile/:profile/load-balanced/:chain POST /rpc/profile/:profile/latency-weighted/:chain POST /rpc/profile/:profile/provider/:provider_id/:chain ``` ### Parameters * `:profile` - Profile slug (e.g., `default`, `testnet`, `production`) ### Example ```bash theme={null} curl -X POST http://localhost:4000/rpc/profile/testnet/fastest/base \ -H 'Content-Type: application/json' \ -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}' ``` Without an explicit profile in the URL, requests automatically use the `"default"` profile. Ensure `config/profiles/default.yml` exists at startup. ## Supported Methods Lasso supports read-only Ethereum JSON-RPC methods: ### Block Methods * `eth_blockNumber` - Latest block number * `eth_getBlockByNumber` - Block data by number * `eth_getBlockByHash` - Block data by hash ### Account Methods * `eth_getBalance` - Account balance * `eth_getTransactionCount` - Account nonce * `eth_getCode` - Contract bytecode ### Transaction Methods * `eth_getTransactionByHash` - Transaction details * `eth_getTransactionReceipt` - Transaction receipt ### Call Methods * `eth_call` - Read-only contract call * `eth_estimateGas` - Gas estimation ### State Methods * `eth_getLogs` - Historical log queries * `eth_getStorageAt` - Storage slot value ### Gas & Fee Methods * `eth_gasPrice` - Current gas price * `eth_maxPriorityFeePerGas` - EIP-1559 priority fee * `eth_feeHistory` - Historical fee data ### Metadata Methods * `eth_chainId` - Chain ID (served locally, no upstream call) ## Unsupported Methods ### Subscription Methods Subscription methods (`eth_subscribe`, `eth_unsubscribe`) are rejected over HTTP with a WebSocket URL hint: ```json theme={null} { "jsonrpc": "2.0", "id": 1, "error": { "code": -32601, "message": "Method not supported over HTTP. Use WebSocket connection for subscriptions.", "data": {"websocket_url": "/ws/rpc/ethereum"} } } ``` ### Write Methods Write methods (`eth_sendRawTransaction`, `eth_sendTransaction`) are not currently supported. ## Request Headers ### Required Headers | Header | Value | Description | | -------------- | ------------------ | ----------------- | | `Content-Type` | `application/json` | JSON request body | ### Optional Headers | Header | Example | Description | | ---------------------- | --------------------- | ------------------------------ | | `X-Lasso-Api-Key` | `lasso_abc123` | API key authentication | | `Authorization` | `Bearer lasso_abc123` | Bearer token authentication | | `X-Lasso-Provider` | `alchemy` | Override provider selection | | `X-Lasso-Transport` | `http` or `ws` | Force transport selection | | `X-Lasso-Include-Meta` | `headers` or `body` | Request observability metadata | ### Provider Override Header You can specify a provider via header instead of URL path: ```bash theme={null} curl -X POST http://localhost:4000/rpc/ethereum \ -H 'Content-Type: application/json' \ -H 'X-Lasso-Provider: alchemy' \ -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}' ``` ## Query Parameters | Parameter | Values | Description | | -------------- | ---------------------------------------------- | --------------------------- | | `key` | `lasso_...` | API key for authentication | | `include_meta` | `headers`, `body` | Return routing metadata | | `transport` | `http`, `ws` | Force transport selection | | `provider` | provider ID | Override provider selection | | `strategy` | `fastest`, `load_balanced`, `latency_weighted` | Override routing strategy | ### Strategy Query Parameter ```bash theme={null} curl -X POST 'http://localhost:4000/rpc/ethereum?strategy=fastest' \ -H 'Content-Type: application/json' \ -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}' ``` ## Response Format ### Success Response ```json theme={null} { "jsonrpc": "2.0", "id": 1, "result": "0x8471c9a" } ``` ### Error Response ```json theme={null} { "jsonrpc": "2.0", "id": 1, "error": { "code": -32602, "message": "Invalid params: unsupported chain" } } ``` ### Error Codes \| Code | Meaning | \|------|---------|| \| `-32700` | Parse error (malformed JSON) | \| `-32600` | Invalid Request (missing fields, batch too large) | \| `-32601` | Method not found or not supported on this transport | \| `-32602` | Invalid params (unsupported chain, missing chain\_id) | \| `-32603` | Internal error | \| `-32000` | Server error (rate limit, strategy access denied, quota exceeded) | ## Response Headers ### Standard Headers | Header | Description | | -------------- | ------------------ | | `Content-Type` | `application/json` | | `X-Request-Id` | Phoenix request ID | ### Observability Headers With `include_meta=headers`: | Header | Description | | -------------------- | ---------------------------------- | | `X-Lasso-Request-ID` | Lasso request tracking ID | | `X-Lasso-Meta` | Base64url-encoded routing metadata | ## CORS All origins are allowed (`*`). Allowed headers: * `Content-Type` * `Authorization` * `X-Requested-With` * `X-Lasso-Provider` * `X-Lasso-Transport` * `X-Lasso-Api-Key` Preflight responses are cached for 24 hours.