> ## Documentation Index > Fetch the complete documentation index at: https://voltaire.tevm.sh/llms.txt > Use this file to discover all available pages before exploring further. # Abi > Application Binary Interface encoding and decoding for Ethereum smart contracts Run ABI examples in the interactive playground # Abi Complete Application Binary Interface (ABI) encoding and decoding with type safety for Ethereum smart contracts. Start with [ABI Fundamentals](/primitives/abi/fundamentals) to learn about function selectors, encoding rules, and event structure. ## Overview Branded array of ABI items (functions, events, errors, constructors). Zero-overhead design supports both tree-shakeable methods and class instances, following the same pattern as [Address](/primitives/address). ## Quick Start ```typescript theme={null} import * as Abi from 'tevm/Abi'; import * as S from 'effect/Schema'; import * as AbiSchema from 'voltaire-effect/primitives/Abi'; // Define function ABI item const transferAbi = { type: 'function', name: 'transfer', inputs: [ { type: 'address', name: 'to' }, { type: 'uint256', name: 'amount' } ], outputs: [{ type: 'bool' }], stateMutability: 'nonpayable' } as const; // Get function selector (4 bytes) const selector = Abi.Function.getSelector(transferAbi); // 0xa9059cbb // Encode parameters const encoded = Abi.Function.encodeParams(transferAbi, [ '0x742d35Cc6634C0532925a3b844Bc9e7595f51e3e', 1000000000000000000n ]); ``` ```typescript theme={null} import * as Abi from 'tevm/Abi'; // Define event ABI item const transferEvent = { type: 'event', name: 'Transfer', inputs: [ { type: 'address', name: 'from', indexed: true }, { type: 'address', name: 'to', indexed: true }, { type: 'uint256', name: 'value', indexed: false } ] } as const; // Decode log from transaction receipt const decoded = Abi.Event.decodeLog(transferEvent, { topics: [ '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef', '0x000000000000000000000000742d35cc6634c0532925a3b844bc9e7595f51e3e', '0x000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa96045' ], data: '0x0000000000000000000000000000000000000000000000000de0b6b3a7640000' }); // { from: '0x742d...', to: '0xd8dA...', value: 1000000000000000000n } ``` ```typescript theme={null} import * as Abi from 'tevm/Abi'; // ERC-20 ABI (partial) const erc20Abi = S.decodeUnknownSync(AbiSchema.fromArray)([ { type: 'function', name: 'transfer', inputs: [ { type: 'address', name: 'to' }, { type: 'uint256', name: 'amount' } ], outputs: [{ type: 'bool' }], stateMutability: 'nonpayable' }, { type: 'event', name: 'Transfer', inputs: [ { type: 'address', name: 'from', indexed: true }, { type: 'address', name: 'to', indexed: true }, { type: 'uint256', name: 'value' } ] } ]); // Get specific item by name and type const transferFn = Abi.getItem(erc20Abi, 'transfer', 'function'); const transferEvt = Abi.getItem(erc20Abi, 'Transfer', 'event'); ``` ## Types ```typescript theme={null} // Main ABI type: array of ABI items export type Abi = ReadonlyArray< Function | Event | BrandedError | Constructor | Fallback | Receive > // Example ABI const erc20Abi: Abi = [ { type: "function", name: "transfer", stateMutability: "nonpayable", inputs: [ { type: "address", name: "to" }, { type: "uint256", name: "amount" } ], outputs: [{ type: "bool" }] }, { type: "event", name: "Transfer", inputs: [ { type: "address", name: "from", indexed: true }, { type: "address", name: "to", indexed: true }, { type: "uint256", name: "value" } ] } ] ``` Source: [Abi.ts:49-51](https://github.com/evmts/voltaire/blob/main/src/primitives/Abi/Abi.ts#L49-L51) ```typescript theme={null} export type Parameter< TType extends AbiType = AbiType, TName extends string = string, TInternalType extends string = string > = { type: TType name?: TName internalType?: TInternalType indexed?: boolean // For event parameters components?: readonly Parameter[] // For tuples } // Type conversion utilities export type ParametersToPrimitiveTypes export type ParametersToObject ``` Source: [Parameter.ts:9-41](https://github.com/evmts/voltaire/blob/main/src/primitives/Abi/Parameter.ts#L9-L41) ```typescript theme={null} // All supported Solidity types export type AbiType = // Unsigned integers | "uint" | "uint8" | "uint16" | "uint24" | "uint32" | "uint40" | "uint48" | "uint56" | "uint64" | "uint72" | "uint80" | "uint88" | "uint96" | "uint104" | "uint112" | "uint120" | "uint128" | "uint136" | "uint144" | "uint152" | "uint160" | "uint168" | "uint176" | "uint184" | "uint192" | "uint200" | "uint208" | "uint216" | "uint224" | "uint232" | "uint240" | "uint248" | "uint256" // Signed integers | "int" | "int8" | "int16" | "int24" | "int32" | "int40" | "int48" | "int56" | "int64" | "int72" | "int80" | "int88" | "int96" | "int104" | "int112" | "int120" | "int128" | "int136" | "int144" | "int152" | "int160" | "int168" | "int176" | "int184" | "int192" | "int200" | "int208" | "int216" | "int224" | "int232" | "int240" | "int248" | "int256" // Other types | "address" | "bool" | "string" | "bytes" // Fixed-size bytes | "bytes1" | "bytes2" | "bytes3" | "bytes4" | "bytes5" | "bytes6" | "bytes7" | "bytes8" | "bytes9" | "bytes10" | "bytes11" | "bytes12" | "bytes13" | "bytes14" | "bytes15" | "bytes16" | "bytes17" | "bytes18" | "bytes19" | "bytes20" | "bytes21" | "bytes22" | "bytes23" | "bytes24" | "bytes25" | "bytes26" | "bytes27" | "bytes28" | "bytes29" | "bytes30" | "bytes31" | "bytes32" // Tuple and arrays | "tuple" | `${string}[]` // Dynamic arrays | `${string}[${number}]` // Fixed arrays ``` Source: [Type.ts:1-107](https://github.com/evmts/voltaire/blob/main/src/primitives/Abi/Type.ts#L1-L107) ```typescript theme={null} // Function item export type Function< TName extends string = string, TStateMutability extends StateMutability = StateMutability, TInputs extends readonly Parameter[] = readonly Parameter[], TOutputs extends readonly Parameter[] = readonly Parameter[] > = { type: "function" name: TName stateMutability: TStateMutability inputs: TInputs outputs: TOutputs } // Event item export type Event< TName extends string = string, TInputs extends readonly Parameter[] = readonly Parameter[] > = { type: "event" name: TName inputs: TInputs anonymous?: boolean } // Error item export type BrandedError< TName extends string = string, TInputs extends readonly Parameter[] = readonly Parameter[] > = { type: "error" name: TName inputs: TInputs } // Constructor item export type BrandedConstructor< TStateMutability extends StateMutability = StateMutability, TInputs extends readonly Parameter[] = readonly Parameter[] > = { type: "constructor" stateMutability: TStateMutability inputs: TInputs } // Fallback and Receive export type Fallback< TStateMutability extends StateMutability = StateMutability > = { type: "fallback" stateMutability: TStateMutability } export type Receive = { type: "receive" stateMutability: "payable" } // State mutability export type StateMutability = "pure" | "view" | "nonpayable" | "payable" ``` ## API Documentation ### Core Concepts Learn ABI encoding structure, selectors, and data layout Function, Event, Error, Constructor type definitions ABI encoding and decoding mechanics Function selectors and event topic hashes Common patterns: contract calls, log parsing ### Top-Level Methods Format ABI item to human-readable signature Format with concrete argument values Find ABI item by name and type Generic ABI encoding for any item type Generic ABI decoding for any item type Decode without selector prefix Parse multiple event logs using full ABI ### Function Methods Get function selector (4 bytes) Get human-readable function signature Encode function input parameters Decode function input parameters Encode function return values Decode function return values Factory for custom keccak256 ### Event Methods Get event selector (32 bytes, topic0) Get human-readable event signature Encode indexed parameters to topics Decode event log data and topics Factory for custom keccak256 Factory for custom keccak256 ### Error Methods Get error selector (4 bytes) Get human-readable error signature Encode error parameters Decode error parameters Factory for custom keccak256 ### Constructor Methods Encode constructor parameters for deployment Decode constructor parameters from bytecode ### Item Utilities Type guard: check if item is function Type guard: check if item is event Type guard: check if item is error Type guard: check if item is constructor Type guard: check if item is fallback Type guard: check if item is receive Format ABI item to signature string Format with concrete argument values Get specific item from ABI by name/type ## ABI JSON Format Contract ABIs are typically JSON arrays describing the contract interface: ```typescript theme={null} const abi = [ { "type": "function", "name": "transfer", "stateMutability": "nonpayable", "inputs": [ { "type": "address", "name": "to" }, { "type": "uint256", "name": "amount" } ], "outputs": [{ "type": "bool" }] }, { "type": "event", "name": "Transfer", "inputs": [ { "type": "address", "name": "from", "indexed": true }, { "type": "address", "name": "to", "indexed": true }, { "type": "uint256", "name": "value", "indexed": false } ] }, { "type": "error", "name": "InsufficientBalance", "inputs": [ { "type": "uint256", "name": "balance" }, { "type": "uint256", "name": "required" } ] } ] ``` ## Error Types ```typescript theme={null} import { AbiEncodingError, AbiDecodingError, AbiParameterMismatchError, AbiItemNotFoundError, AbiInvalidSelectorError } from '@tevm/primitives/Abi' try { const encoded = encodeParameters(params, values) } catch (error) { if (error instanceof AbiEncodingError) { // Invalid encoding (out of range, wrong type, etc.) } else if (error instanceof AbiParameterMismatchError) { // Parameter count mismatch } } ``` Source: [Errors.ts:1-35](https://github.com/evmts/voltaire/blob/main/src/primitives/Abi/Errors.ts#L1-L35) ## Tree-Shaking Import only what you need for optimal bundle size: ```typescript theme={null} // Import specific namespace import { Function } from '@tevm/primitives/Abi' // Or import individual functions import { encodeParameters, decodeParameters } from '@tevm/primitives/Abi' ``` ## Sub-Namespaces The Abi module is organized into specialized sub-namespaces: * **Function** - Function encoding/decoding and selectors * **Event** - Event log encoding/decoding and topics * **Error** - Custom error encoding/decoding * **Constructor** - Constructor parameter encoding * **Wasm** - WASM-accelerated implementations Each namespace provides focused functionality with tree-shakeable exports. ## Related Types * [Abi (Effect)](https://voltaire-effect.tevm.sh/primitives/abi) - Effect.ts integration with Schema validation * [Keccak256](/crypto/keccak256) - Keccak256 hashing used for selectors and signatures * [Address](/primitives/address) - 20-byte Ethereum addresses used in ABI encoding * [Uint](/primitives/uint) - Unsigned integer types used in ABI encoding * [Bytes](/primitives/bytes) - Fixed and dynamic byte arrays in ABI encoding ## Specification References * [Solidity ABI Specification](https://docs.soliditylang.org/en/latest/abi-spec.html) - Official ABI encoding specification * [Contract ABI Specification](https://docs.soliditylang.org/en/latest/abi-spec.html#json) - JSON ABI format * [EIP-712](https://eips.ethereum.org/EIPS/eip-712) - Typed structured data hashing and signing