solc-js

0.8.35 verified Fri May 01 auth: no javascript

JavaScript bindings for the Solidity compiler (solc), providing a high-level and low-level API to compile Solidity smart contracts to EVM bytecode. The current stable version is 0.8.35, following the Solidity compiler releases closely. It uses Emscripten-compiled Solidity binaries from solc-bin, supporting all compiler features via the Standard JSON interface. Key differentiators: it's the official JavaScript wrapper for Solidity, enabling dynamic compilation in Node.js and browser environments without a native binary. The package ships TypeScript types and supports both CommonJS and ESM modules (ESM requires Node >=12).

Common errors

error Error: No input specified ↓

cause compile() called without arguments or with invalid input.

fix

Ensure input is a non-empty JSON string with 'language', 'sources', and 'settings' fields.

error TypeError: solc.compile is not a function ↓

cause Import style mismatch (e.g., using default import when only named export exists).

fix

Use import { compile } from 'solc' instead of import solc from 'solc'.

error Module not found: Can't resolve 'solc' ↓

cause Package not installed or ESM resolution issue (package not in node_modules).

fix

Run 'npm install solc' and ensure Node.js version >=12 for ESM or use CommonJS require.

error solc.compile is not a function (when using require) ↓

cause Older solc versions (pre-0.8.11) had different export shape.

fix

Use solc.compile() directly (it always was a function) or upgrade to >=0.8.11 and use named export.

Warnings

breaking Breaking change in v0.8.11: compile() now returns JSON string instead of object. Wrap with JSON.parse. ↓

fix Wrap compile() call with JSON.parse() to get the output object.

deprecated Legacy callback-based API removed in v0.8.0. Use compile(input, { import: ... }) object syntax. ↓

fix Update to use the object-based callback parameter: compile(input, { import: myImportFn }).

gotcha The import callback must be synchronous. Async callbacks will cause undefined behavior. ↓

fix Pre-fetch all dependencies synchronously or use a synchronous file reader.

breaking Version 0.6.0 dropped support for Node <6. Node 12+ required for ESM support. ↓

fix Upgrade Node.js to >=10 (preferably >=12 for ESM).

deprecated solcjs CLI is not compatible with native solc CLI. It lacks some features. ↓

fix Use native solc binary for full feature set or rely on solc-js CLI for simple compilation.

Install

npm install solc

yarn add solc

pnpm add solc

Imports

compile
wrong
```
const solc = require('solc'); solc.compile(...)
```
correct
```
import { compile } from 'solc'
```
ESM named import available since v0.8.11; CJS still works but TypeScript prefers named import for type safety.
default
wrong
```
import * as solc from 'solc'
```
correct
```
import solc from 'solc'
```
Default export is the main module but TypeScript may need allowSyntheticDefaultImports or esModuleInterop. Prefer named imports.
compileCallback
```
import { compileCallback } from 'solc'
```
Only available via named import; used for low-level API with callback imports.
version
wrong
```
const solc = require('solc'); console.log(solc.version)
```
correct
```
import { version } from 'solc'
```
Exported as a function that returns the compiler version string; CJS require() also works.

Quickstart

Compiles a simple Solidity contract using the high-level API with Standard JSON input.

import { compile } from 'solc';

const input = {
  language: 'Solidity',
  sources: {
    'test.sol': {
      content: 'contract C { function f() public { } }'
    }
  },
  settings: {
    outputSelection: {
      '*': {
        '*': ['evm.bytecode.object']
      }
    }
  }
};

const output = JSON.parse(compile(JSON.stringify(input)));
console.log(output.contracts['test.sol'].C.evm.bytecode.object);