solc-js

0.8.1 verified Fri May 01 auth: no javascript

JavaScript bindings for the Solidity compiler, enabling Solidity smart contract compilation directly in Node.js or the browser via Emscripten. This version 0.8.1 is a fixed release of the official npm package by the Ethereum Foundation. It provides both a high-level API (uniform `compile` method using Standard JSON I/O) and a low-level API exposing compiler internals. Key differentiators: it wraps the native Solidity compiler, supports imports via callbacks, and the command-line interface (`solcjs`) is not compatible with the native `solc` binary. Major breaking changes include the removal of the old callback-based API since v0.6.0. Regular releases track Solidity compiler versions.

Common errors

error Error: Requires at least one source file. ↓

cause solcjs called without specifying a .sol file.

fix

Provide the contract file: solcjs --bin MyContract.sol

error Error: solc: TypeError: Cannot read property 'compile' of undefined ↓

cause Incorrect import: using default import instead of named import in ESM.

fix

Use import { compile } from 'solc'; or const { compile } = require('solc');

error Error: Source file requires different compiler version (current compiler is 0.8.1) ↓

cause Contract pragma does not match installed solc version.

fix

Install the correct solc version matching the pragma, e.g., npm install solc@0.8.1 or pragma solidity ^0.8.0.

Warnings

breaking The callback-based API (passing a function as second argument to compile) is removed. Use the object-based interface with `import` callback instead. ↓

fix Pass an object with `import` and `smtSolver` keys, not a direct function.

gotcha solcjs command-line tool is incompatible with the native solc binary and cannot be used with eth.compile.solidity(). ↓

fix Use the native Solidity compiler for RPC-based compilation or switch to solc-js high-level API.

gotcha The `import` callback must be synchronous. Asynchronous filesystem access will cause issues. ↓

fix Resolve dependencies synchronously or pre-collect them.

deprecated The `smtSolver` callback may not be supported in future versions. ↓

fix Avoid relying on SMT solver integration; use external tools.

Install

npm install solc-0.8.1-fixed

yarn add solc-0.8.1-fixed

pnpm add solc-0.8.1-fixed

Imports

compile
wrong
```
import solc from 'solc';
```
correct
```
import { compile } from 'solc';
```
Default export is not available; use named import. In CommonJS, use const { compile } = require('solc').
solc
wrong
```
import solc from 'solc';
```
correct
```
import * as solc from 'solc';
```
For low-level API access (e.g., solc.compile, solc.semver()), use namespace import. Default import is not supported.
require('solc')
wrong
```
const { compile } = require('solc');
```
correct
```
const solc = require('solc');
```
CommonJS require returns the module with compile, semver, etc. Object destructuring works in Node >= 8.

Quickstart

Compiles a minimal Solidity contract using the high-level API and prints the bytecode.

const solc = require('solc');
const input = {
  language: 'Solidity',
  sources: {
    'test.sol': { content: 'contract C { function f() public { } }' }
  },
  settings: { outputSelection: { '*': { '*': ['*'] } } }
};
const output = JSON.parse(solc.compile(JSON.stringify(input)));
for (const contractName in output.contracts['test.sol']) {
  console.log(`${contractName}: ${output.contracts['test.sol'][contractName].evm.bytecode.object}`);
}