# Migrate from Prettier to bun fmt `bun fmt` reads your `.prettierrc` and prints what Prettier 3 prints. In most projects you only change the command. Start with `--doctor`. It shows what Bun will do with your config, and it doesn't format or write anything. ```sh terminal icon="terminal" bun fmt --doctor ``` ```txt Using .prettierrc (Prettier config) 4 files are formatted natively Built-in plugins: @ianvs/prettier-plugin-sort-imports You can remove: @ianvs/prettier-plugin-sort-imports Still needed: prettier (the "format" script runs it) Not checked: other tools' configs, CI files, Git hooks ``` --- Change the scripts. ```json package.json icon="file-json" { "scripts": { "format": "prettier --write .", // [!code --] "format:check": "prettier --check .", // [!code --] "format": "bun fmt", // [!code ++] "format:check": "bun fmt --check" // [!code ++] } } ``` `bun fmt` writes by default and formats the current directory, so `--write .` goes away. Other flags and arguments stay the same. Change CI and Git hooks too. If your script is called `fmt`, don't skip this: `bun fmt` runs a `fmt` script when `package.json` has one, so you'd still get Prettier. Watch out for two differences in hooks and shell scripts: - **No arguments means the current directory.** Prettier prints an error there. So if the file list can be empty, as in `git diff --cached --name-only | xargs bun fmt` or `bun fmt $(git ls-files '*.foo')`, Bun formats everything. Use `bun fmt --staged` in a pre-commit hook, or `xargs -r`. - **`bun fmt file.ts` writes the file and prints its name.** `prettier file.ts` prints the formatted code. To print it, pipe the code in: `bun fmt --stdin-filepath file.ts < file.ts`. Piping into `--parser` works like in Prettier: `generate | bun fmt --parser typescript > out.ts`. --- Check that nothing changes. With a Prettier config, `--check` prints what Prettier prints. ```sh terminal icon="terminal" bun fmt --check ``` ```txt $ bun fmt --check Checking formatting... All matched files use Prettier code style! ``` --- Run `--doctor` again. No script runs Prettier anymore, so it can go too. ```txt You can remove: @ianvs/prettier-plugin-sort-imports, prettier Not checked: other tools' configs, CI files, Git hooks ``` ```sh terminal icon="terminal" bun remove prettier @ianvs/prettier-plugin-sort-imports ``` Leave `.prettierrc` as it is, including `plugins`. Keep `prettier` if your editor's Prettier extension uses it. --- Bun reads everything Prettier reads: - `.prettierrc` in JSON, YAML, TOML, JavaScript, or TypeScript, `prettier.config.*`, and `"prettier"` in `package.json`, with `overrides` - `.editorconfig`, and the `.prettierignore` and `.gitignore` in the current directory - `// prettier-ignore` comments and the `@format` and `@noformat` pragmas - Every flag of Prettier 3 except `--file-info` and `--support-info` --- Bun doesn't load Prettier plugins. These are built in, with all their options, so leave them in `plugins`: - `prettier-plugin-tailwindcss` - `@trivago/prettier-plugin-sort-imports` - `@ianvs/prettier-plugin-sort-imports` - `prettier-plugin-organize-imports` - `@prettier/plugin-oxc` - `prettier-plugin-svelte` - `prettier-plugin-packagejson` Svelte files are formatted the way `prettier-plugin-svelte` 4.1.1 formats them, whichever version you have installed. Other versions print a few components differently, so expect a small diff the first time if you were on one. The plugin's options are those of 4.1.1: `svelteSortOrder`, `svelteAllowShorthand`, and `svelteIndentScriptAndStyle`. 4.1.1 has no `svelteStrictMode`, so Bun ignores it with a warning, like any unknown option. With `rangeStart` or `rangeEnd`, a Svelte file is left unchanged, like an HTML or CSS file, because Prettier can't format part of one. To leave Svelte files alone, set [`svelte = false` in `bunfig.toml`](/runtime/bunfig#format-svelte). `package.json` keys are sorted the way `prettier-plugin-packagejson` 3.0.2 sorts them with `sort-package-json` 3.7.1, and `packageSortOrder` is supported. Bun puts the keys where the plugin puts them and leaves every value as you wrote it. The plugin parses the file and writes it back, which turns `1.0` into `1`, `12345678901234567890` into `12345678901234567000`, and `"\u00e9"` into `"é"`. It also drops all but the last of two members with the same key, and moves keys like `"10"` to the front of their object. Bun does none of that. It also sorts a file with a trailing comma, where the plugin throws. --- Astro and other languages that come from a plugin go to your installed Prettier. Keep `prettier` and every plugin in `plugins` installed. `--doctor` shows which files those are. ```txt Using .prettierrc (Prettier config) 3 files are formatted natively 1 file goes to your installed Prettier: 1 *.astro Built-in plugins: @ianvs/prettier-plugin-sort-imports Plugins that use your installed Prettier: prettier-plugin-astro Still needed: @ianvs/prettier-plugin-sort-imports, prettier, prettier-plugin-astro (some files go to them) ``` --- With any other plugin, Bun skips the files that config covers and exits with code `2`. A plugin could print them differently, and Bun won't guess. Pass `--allow-unsupported` to format them without the plugin. ```txt error: 3 files were not formatted because the Prettier config uses plugins that bun fmt does not include: prettier-plugin-brace-style Use --allow-unsupported to format them without the plugins. ``` --- You don't have to keep `.prettierrc`. Move the options to [`bunfig.toml`](/format#options), under the same names, and delete the file. `overrides` become [`[[fmt.overrides]]`](/runtime/bunfig#format-overrides). ```toml bunfig.toml icon="settings" [fmt] semi = false singleQuote = true ``` Without a Prettier config, `bun fmt` also formats TOML files, formats Svelte files without the plugin in a config, and `--check` prints a shorter report. --- ## Differences from Prettier If `bun fmt` and Prettier 3 print different code, that's a bug. [Open an issue](https://github.com/oven-sh/bun/issues). These differences are intentional: - **It writes by default.** `--write` is accepted and does nothing. - **No arguments means the current directory.** - **Only changed files are listed**, followed by a summary on stderr. - **An unknown flag is an error.** Prettier warns and continues. - **`--cache` does nothing.** Every run formats every file. - **Exit code `2` means something went wrong**, like a syntax error or a skipped file. Prettier uses `1` for some of these. - **Bytes that aren't valid UTF-8 are kept.** Prettier replaces them. - **Where Prettier's output changes what a file means, Bun's differs.** That's rare. In a Handlebars template Prettier drops ``, and it joins the lines of a `