Formatters

OpenCode can format files after they are written or edited using language-specific formatters. Formatters are disabled by default; enable them in your config before OpenCode will run them.

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Built-in

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

When formatters are enabled, OpenCode will use prettier for matching files if your project has prettier in package.json.

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How it works

When OpenCode writes or edits a file and formatters are enabled, it:

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

This process happens in the background for enabled formatters.

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Configure

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

To enable all built-in formatters, set formatter to true.

opencode.json

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

Use an object to keep built-ins enabled while configuring overrides or custom formatters.

opencode.json

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

Each formatter configuration supports the following:

Property	Type	Description
disabled	boolean	Set this to true to disable the formatter
command	string[]	The command to run for formatting. Required for custom formatters; optional for built-ins.
environment	object	Environment variables to set when running the formatter
extensions	string[]	File extensions this formatter should handle

Let’s look at some examples.

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Disabling formatters

If formatter is omitted, all formatters are disabled. To disable all formatters after another config enabled them, 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 configure built-in formatters with options like environment or extensions. To add a custom formatter, specify a command and 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.