Formatters

OpenCode uses language specific formatters

OpenCode automatically formats files after they are written or edited using language-specific formatters. This ensures that the code that is generated follows the code styles of your project.

Built-in Formatters

OpenCode comes with several built-in formatters for popular languages and frameworks. Below is a list of the formatters, supported file extensions, and commands or config options it needs.

Formatter	Extensions	Requirements
air	.R	air command available
biome	.js, .jsx, .ts, .tsx, .html, .css, .md, .json, .yaml, and more	biome.json(c) config file
cargofmt	.rs	cargo fmt command available
clang-format	.c, .cpp, .h, .hpp, .ino, and more	.clang-format config file
cljfmt	.clj, .cljs, .cljc, .edn	cljfmt command available
dart	.dart	dart command available
dfmt	.d	dfmt command available
gleam	.gleam	gleam command available
gofmt	.go	gofmt command available
htmlbeautifier	.erb, .html.erb	htmlbeautifier command available
ktlint	.kt, .kts	ktlint command available
mix	.ex, .exs, .eex, .heex, .leex, .neex, .sface	mix command available
nixfmt	.nix	nixfmt command available
ocamlformat	.ml, .mli	ocamlformat command available and .ocamlformat config file
ormolu	.hs	ormolu command available
oxfmt (Experimental)	.js, .jsx, .ts, .tsx	oxfmt dependency in package.json and an experimental env variable flag
pint	.php	laravel/pint dependency in composer.json
prettier	.js, .jsx, .ts, .tsx, .html, .css, .md, .json, .yaml, and more	prettier dependency in package.json
rubocop	.rb, .rake, .gemspec, .ru	rubocop command available
ruff	.py, .pyi	ruff command available with config
rustfmt	.rs	rustfmt command available
shfmt	.sh, .bash	shfmt command available
standardrb	.rb, .rake, .gemspec, .ru	standardrb command available
terraform	.tf, .tfvars	terraform command available
uv	.py, .pyi	uv command available
zig	.zig, .zon	zig command available

So if your project has prettier in your package.json, OpenCode will automatically use it.

How It Works

When OpenCode writes or edits a file, it:

1. Checks the file extension against all enabled formatters.
2. Runs the appropriate formatter command on the file.
3. Applies the formatting changes automatically.

This process happens in the background, ensuring your code styles are maintained without any manual steps.

Configure Formatters

You can customize formatters through the formatter section in your OpenCode config.

opencode.json

{
  "$schema": "https://opencode.ai/config.json",
  "formatter": {}
}

Each formatter configuration supports the following:

formatter.{name}.disabled · boolean

Set this to true to disable the formatter.

formatter.{name}.command · string[]

The command to run for formatting. Use $FILE as a placeholder for the file path.

formatter.{name}.environment · object

Environment variables to set when running the formatter.

formatter.{name}.extensions · string[]

File extensions this formatter should handle.

Disabling Formatters

To disable all formatters globally, set formatter to false:

opencode.json

{
  "$schema": "https://opencode.ai/config.json",
  "formatter": false
}

To disable a specific formatter, set disabled to true:

opencode.json

{
  "$schema": "https://opencode.ai/config.json",
  "formatter": {
    "prettier": {
      "disabled": true
    }
  }
}

Custom Formatters

You can override the built-in formatters or add new ones by specifying the command, environment variables, and file extensions:

opencode.json

{
  "$schema": "https://opencode.ai/config.json",
  "formatter": {
    "prettier": {
      "command": ["npx", "prettier", "--write", "$FILE"],
      "environment": {
        "NODE_ENV": "development"
      },
      "extensions": [".js", ".ts", ".jsx", ".tsx"]
    },
    "custom-markdown-formatter": {
      "command": ["deno", "fmt", "$FILE"],
      "extensions": [".md"]
    }
  }
}

The $FILE placeholder in the command will be replaced with the path to the file being formatted.

Examples

Override Prettier Configuration

opencode.json

{
  "$schema": "https://opencode.ai/config.json",
  "formatter": {
    "prettier": {
      "command": ["npx", "prettier", "--write", "--single-quote", "$FILE"],
      "environment": {
        "NODE_ENV": "production"
      }
    }
  }
}

Add Custom Python Formatter

opencode.json

{
  "$schema": "https://opencode.ai/config.json",
  "formatter": {
    "black": {
      "command": ["black", "$FILE"],
      "extensions": [".py"]
    }
  }
}

Configure Multiple Formatters

opencode.json

{
  "$schema": "https://opencode.ai/config.json",
  "formatter": {
    "prettier": {
      "command": ["npx", "prettier", "--write", "$FILE"],
      "extensions": [".js", ".ts", ".jsx", ".tsx"]
    },
    "gofmt": {
      "command": ["gofmt", "-w", "$FILE"],
      "extensions": [".go"]
    },
    "rustfmt": {
      "command": ["rustfmt", "$FILE"],
      "extensions": [".rs"]
    }
  }
}