> ## Documentation Index > Fetch the complete documentation index at: https://docs.sqd.dev/llms.txt > Use this file to discover all available pages before exploring further. # Generating utility modules > Generate task-specific utility modules typegen — produce typed clients for EVM ABIs and Substrate metadata. The `squid-evm-typegen(1)` tool generates TypeScript facades for EVM transactions, logs and `eth_call` queries. The generated facades are assumed to be used by squids indexing EVM data. The tool takes a JSON ABIs as an input. Those can be specified in three ways: 1. as a plain JSON file(s): ```bash theme={"system"} npx squid-evm-typegen src/abi abi/erc20.json ``` To include all files in `./abi` and add an interface for the Multicall contract, run ```bash theme={"system"} npx squid-evm-typegen ./src/abi ./abi/*.json --multicall ``` You can get JSON ABIs for explorer (Etherscan, Bscscan etc) verified contract by visiting the contract page, going to the "Contract" tab and scrolling down to the "Contract ABI" section. *Do not use the "Export ABI" function!* Copy the contents to the clipboard and paste them to a new JSON file. 2. **(requires an Etherscan API key)** as a contract address. One can pass multiple addresses at once. ```bash theme={"system"} npx squid-evm-typegen --etherscan-api-key src/abi 0xBB9bc244D798123fDe783fCc1C72d3Bb8C189413 ``` Please check if your contract is a proxy when using this method. If it is, consult [this page](/en/sdk/squid-sdk/resources/evm/proxy-contracts) for guidance. 3. as an arbitrary URL: ```bash theme={"system"} npx squid-evm-typegen src/abi https://example.com/erc721.json ``` In all cases typegen will use `basename` of the ABI as the root name for the generated files. You can change the basename of generated files using the fragment `(#)` suffix. ```bash theme={"system"} squid-evm-typegen src/abi 0xBB9bc244D798123fDe783fCc1C72d3Bb8C189413#my-contract-name ``` **Arguments:** | | | | ------------ | --------------------------------------------------------------------------------------- | | `output-dir` | output directory for generated definitions | | `abi` | A contract address, an URL or a local path to the ABI file. Accepts multiple contracts. | **Options:** | | | | ----------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `--multicall` | generate a facade for the MakerDAO multicall contract. May significantly improve the performance of contract state calls by [batching RPC requests](/en/sdk/squid-sdk/resources/tools/typegen/state-queries#batch-state-queries) | | `--etherscan-api ` | etherscan API to fetch contract ABI by a known address. By default, `https://api.etherscan.io/` | | `--clean` | delete output directory before the run | | `-h, --help` | display help for command | The generated modules depend on `@subsquid/evm-abi`. Please add it to your `package.json` as a peer dependency if it's not there already: `bash npm i @subsquid/evm-abi ` ## Usage The generated utility modules have three intended uses: 1. Constants: EVM log topic0 values and sighashes for transactions. Example: ```ts theme={"system"} // generated by evm-typegen import * as weth from "./abi/weth"; const CONTRACT_ADDRESS = "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2".toLowerCase(); const processor = new EvmBatchProcessor() .setGateway("https://v2.archive.subsquid.io/network/ethereum-mainnet") .addLog({ address: [CONTRACT_ADDRESS], topic0: [weth.events.Deposit.topic, weth.events.Withdrawal.topic], }); ``` 2. [Decoding of EVM logs and transactions](/en/sdk/squid-sdk/resources/tools/typegen/decoding) 3. [Direct chain state queries](/en/sdk/squid-sdk/resources/tools/typegen/state-queries), including [queries to multicall](/en/sdk/squid-sdk/resources/tools/typegen/state-queries#batch-state-queries). The substrate typegen tool is a part of Squid SDK. It generates TypeScript wrappers for interfacing Substrate events and calls. Usage: ```bash theme={"system"} npx squid-substrate-typegen typegen.json ``` If necessary, multiple config files can be supplied: ```bash theme={"system"} npx squid-substrate-typegen typegen0.json typegen1.json ... ``` The structure of the `typegen.json` config file is best illustrated with an example: ```json theme={"system"} { "outDir": "src/types", "specVersions": "https://v2.archive.subsquid.io/metadata/kusama", "pallets": { // add one such section for each pallet "Balances": { "events": [ // list of events to generate wrappers for "Transfer" ], "calls": [ // list of calls to generate wrappers for "transfer_allow_death" ], "storage": ["Account"], "constants": ["ExistentialDeposit"] } } } ``` The `specVersions` field is either * a metadata service endpoint URL, like ``` https://v2.archive.subsquid.io/metadata/{network} ``` or * a path to a [`jsonl`](https://jsonlines.org) file generated by [`substrate-metadata-explorer(1)`](https://github.com/subsquid/squid-sdk/tree/master/substrate/substrate-metadata-explorer). To generate all items defined by a given pallet, set any of the `events`, `calls`, `storage` or `constants` fields to `true`, e.g. ```json theme={"system"} { "outDir": "src/types", "specVersions": "kusamaVersions.jsonl", "pallets": { "Balances": { // generate wrappers for all Balances pallet constants "constants": true } } } ``` In the rare cases when the typegen needs a types bundle, supply it alongside metadata: ```json theme={"system"} { "outDir": "src/types", "specVersions": "westendVersions.jsonl", "typesBundle": "westendTypes.json", ... } ``` ## TypeScript wrappers Wrappers generated by the typegen command can be found in the specified `outDir` (`src/types` by convention). Assuming that this folder is imported as `types` (e.g. with `import * as types from './types'`), you'll be able to find the wrappers at: * for events: `types.events.${palletName}.${eventName}` * for calls: `types.calls.${palletName}.${callName}` * for storage items: `types.storage.${palletName}.${storageItemName}` * for constants: `types.constants.${palletName}.${constantName}` All identifiers (pallet name, call name etc) are lowerCamelCased. E.g. the constant `Balances.ExistentialDeposit` becomes `types.events.balances.existentialDeposit` and the call `Balances.set_balance` becomes `types.calls.setBalance`. ## Usage 1. Item name constants (e.g. `events.balances.transfer.name`). 2. Runtime versioning-aware [decoding](/en/sdk/squid-sdk/resources/tools/typegen/decoding). 3. [Chain storage queries](/en/sdk/squid-sdk/resources/tools/typegen/state-queries) 4. Runtime constants: ```typescript theme={"system"} import {constants} from './types' // ... processor.run(new TypeormDatabase(), async ctx => { for (let block of ctx.blocks) { if (constants.balances.existentialDeposit.v1020.is(block.header)) { let c = new constants.balances.existentialDeposit.v1020.get(block.header) ctx.log.info(`Balances.ExistentialDeposit (runtime version V1020): ${c}`) } } }) ``` Use [`squid-ink-typegen`](https://github.com/subsquid/squid-sdk/tree/master/substrate/ink-typegen) to generate facade classes for decoding ink! smart contract data from JSON ABI metadata. Usage: ```bash theme={"system"} npx squid-ink-typegen --abi abi/erc20.json --output src/abi/erc20.ts ``` The generated source code exposes the [decoding methods](/en/sdk/squid-sdk/resources/tools/typegen/decoding), some useful types and a class for performing [wrapped RPC queries](/en/sdk/squid-sdk/resources/tools/typegen/state-queries), using `@subsquid/ink-abi` under the hood