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

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

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

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

{
  "$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 | | 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

To disable all formatters globally, set formatter to false:

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

To disable a specific formatter, set disabled to true:

{
  "$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:

{
  "$schema": "https://opencode.ai/config.json",
  "formatter": {
    "prettier": {
      "command": ["npx", "prettier", "--write", "$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.