# web3-provider-engine > A JavaScript library for composing Ethereum provider objects using middleware modules Latest version **17.0.1** (published 2024-04-22) · MIT license · 0 weekly downloads ## Install ```sh npm install web3-provider-engine pnpm add web3-provider-engine yarn add web3-provider-engine bun add web3-provider-engine ``` ## Health **Score 23/100 (F)** — status: abandoned. Positive: has types package; no vulnerabilities; high quality score. Warnings: low downloads; no esm support. Negative: abandoned; low maintenance score. ## Facts | | | |---|---| | Version | 17.0.1 | | Published | 2024-04-22 | | First published | 2015-12-19 | | Weekly downloads | 0 | | License | MIT | | TypeScript types | separate (@types/web3-provider-engine) | | Module format | CommonJS | | Node | ^16.20 \|\| ^18.16 \|\| >=20 | | Dependencies | 22 | | Unpacked size | 4 MB | | Known vulnerabilities | 0 | | Install scripts | no | | GitHub stars | 601 | | Maintainers | mcmire, nicholasellul, lgbot, naugtur, ritave, danfinlay, kumavis, rekmarks, metamaskbot, gudahtt, brad.decker, sethkfman | ## Links - npm: https://www.npmjs.com/package/web3-provider-engine - Repository: https://github.com/MetaMask/web3-provider-engine - Homepage: https://github.com/MetaMask/web3-provider-engine#readme - Issues: https://github.com/MetaMask/web3-provider-engine/issues - npm.io page: https://npm.io/package/web3-provider-engine ## Dependencies (22) - [ws](https://npm.io/package/ws.md) ^7.5.9 - [xhr](https://npm.io/package/xhr.md) ^2.6.0 - [async](https://npm.io/package/async.md) ^2.6.4 - [clone](https://npm.io/package/clone.md) ^2.1.2 - [xtend](https://npm.io/package/xtend.md) ^4.0.2 - [backoff](https://npm.io/package/backoff.md) ^2.5.0 - [semaphore](https://npm.io/package/semaphore.md) ^1.1.0 - [@ethereumjs/tx](https://npm.io/package/@ethereumjs/tx.md) ^4.2.0 - [@ethereumjs/vm](https://npm.io/package/@ethereumjs/vm.md) ^6.5.0 - [readable-stream](https://npm.io/package/readable-stream.md) ^3.6.2 - [@cypress/request](https://npm.io/package/@cypress/request.md) ^3.0.1 - [@ethereumjs/util](https://npm.io/package/@ethereumjs/util.md) ^8.1.0 - [@ethereumjs/block](https://npm.io/package/@ethereumjs/block.md) ^4.3.0 - [eth-block-tracker](https://npm.io/package/eth-block-tracker.md) ^8.1.0 - [promise-to-callback](https://npm.io/package/promise-to-callback.md) ^1.0.0 - [@metamask/rpc-errors](https://npm.io/package/@metamask/rpc-errors.md) ^6.2.1 - [json-stable-stringify](https://npm.io/package/json-stable-stringify.md) ^1.1.1 - [@metamask/eth-sig-util](https://npm.io/package/@metamask/eth-sig-util.md) ^7.0.1 - [@ethereumjs/statemanager](https://npm.io/package/@ethereumjs/statemanager.md) ^1.1.0 - [@metamask/eth-json-rpc-infura](https://npm.io/package/@metamask/eth-json-rpc-infura.md) ^9.1.0 - [@metamask/eth-json-rpc-filters](https://npm.io/package/@metamask/eth-json-rpc-filters.md) ^7.0.0 - [@metamask/eth-json-rpc-middleware](https://npm.io/package/@metamask/eth-json-rpc-middleware.md) ^12.1.0 ## Recent versions - 17.0.1 (latest) — 2024-04-22 - 16.0.8 — 2024-04-22 - 17.0.0 — 2024-04-18 - 16.0.7 — 2023-10-23 - 16.0.6 — 2023-10-13 - 16.0.5 — 2023-01-04 - 16.0.4 — 2022-04-29 - 16.0.3 — 2021-07-15 - 16.0.2 — 2021-07-15 - 16.0.1 — 2020-09-23 - 16.0.0 — 2020-09-23 - 15.0.12 — 2020-05-28 - 15.0.11 — 2020-05-28 - 15.0.10 — 2020-05-28 - 15.0.9 — 2020-05-26 - … 177 more at https://npm.io/package/web3-provider-engine/versions ## README # Web3 ProviderEngine Web3 ProviderEngine is a tool for composing your own [web3 providers](https://github.com/ethereum/wiki/wiki/JavaScript-API#web3). > [!CAUTION] > This package has been deprecated. > > This package was originally created for MetaMask, but has been replaced by `@metamask/json-rpc-engine`, `@metamask/eth-json-rpc-middleware`, `@metamask/eth-json-rpc-provider`, and various other packages. > > Here is an example of how to create a provider using those packages: > > ```javascript > import { providerFromMiddleware } from '@metamask/eth-json-rpc-provider'; > import { createFetchMiddleware } from '@metamask/eth-json-rpc-middleware'; > import { valueToBytes, bytesToBase64 } from '@metamask/utils'; > import fetch from 'cross-fetch'; > > const rpcUrl = '[insert RPC URL here]'; > > const fetchMiddleware = createFetchMiddleware({ > btoa: (stringToEncode) => bytesToBase64(valueToBytes(stringToEncode)), > fetch, > rpcUrl, > }); > const provider = providerFromMiddleware(fetchMiddleware); > > provider.sendAsync( > { id: 1, jsonrpc: '2.0', method: 'eth_chainId' }, > (error, response) => { > if (error) { > console.error(error); > } else { > console.log(response.result); > } > } > ); > ``` > > This example was written with v12.1.0 of `@metamask/eth-json-rpc-middleware`, v3.0.1 of `@metamask/eth-json-rpc-provider`, and v8.4.0 of `@metamask/utils`. > ### Composable Built to be modular - works via a stack of 'sub-providers' which are like normal web3 providers but only handle a subset of rpc methods. The subproviders can emit new rpc requests in order to handle their own; e.g. `eth_call` may trigger `eth_getAccountBalance`, `eth_getCode`, and others. The provider engine also handles caching of rpc request results. ```js const ProviderEngine = require('web3-provider-engine') const CacheSubprovider = require('web3-provider-engine/subproviders/cache.js') const FixtureSubprovider = require('web3-provider-engine/subproviders/fixture.js') const FilterSubprovider = require('web3-provider-engine/subproviders/filters.js') const VmSubprovider = require('web3-provider-engine/subproviders/vm.js') const HookedWalletSubprovider = require('web3-provider-engine/subproviders/hooked-wallet.js') const NonceSubprovider = require('web3-provider-engine/subproviders/nonce-tracker.js') const RpcSubprovider = require('web3-provider-engine/subproviders/rpc.js') var engine = new ProviderEngine() var web3 = new Web3(engine) // static results engine.addProvider(new FixtureSubprovider({ web3_clientVersion: 'ProviderEngine/v0.0.0/javascript', net_listening: true, eth_hashrate: '0x00', eth_mining: false, eth_syncing: true, })) // cache layer engine.addProvider(new CacheSubprovider()) // filters engine.addProvider(new FilterSubprovider()) // pending nonce engine.addProvider(new NonceSubprovider()) // vm engine.addProvider(new VmSubprovider()) // id mgmt engine.addProvider(new HookedWalletSubprovider({ getAccounts: function(cb){ ... }, approveTransaction: function(cb){ ... }, signTransaction: function(cb){ ... }, })) // data source engine.addProvider(new RpcSubprovider({ rpcUrl: 'https://testrpc.metamask.io/', })) // log new blocks engine.on('block', function(block){ console.log('================================') console.log('BLOCK CHANGED:', '#'+block.number.toString('hex'), '0x'+block.hash.toString('hex')) console.log('================================') }) // network connectivity error engine.on('error', function(err){ // report connectivity errors console.error(err.stack) }) // start polling for blocks engine.start() ``` When importing in webpack: ```js import * as Web3ProviderEngine from 'web3-provider-engine'; import * as RpcSource from 'web3-provider-engine/subproviders/rpc'; import * as HookedWalletSubprovider from 'web3-provider-engine/subproviders/hooked-wallet'; ``` ### Built For Zero-Clients The [Ethereum JSON RPC](https://github.com/ethereum/wiki/wiki/JSON-RPC) was not designed to have one node service many clients. However a smaller, lighter subset of the JSON RPC can be used to provide the blockchain data that an Ethereum 'zero-client' node would need to function. We handle as many types of requests locally as possible, and just let data lookups fallback to some data source ( hosted rpc, blockchain api, etc ). Categorically, we don’t want / can’t have the following types of RPC calls go to the network: * id mgmt + tx signing (requires private data) * filters (requires a stateful data api) * vm (expensive, hard to scale) ## Running tests ```bash yarn test ``` --- _Source: https://npm.io/package/web3-provider-engine · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._