Formatters - Opencode

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.

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.

How it works

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

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

This process happens in the background for enabled formatters.

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.

json

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

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

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.

Disabling formatters

If formatter is omitted, all formatters are disabled. To disable all formatters after another config enabled them, set formatter to false:

json

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

To disable a specific formatter, set disabled to true:

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:

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.