Code Block Formatter
Wrap raw code in a properly-fenced markdown code block — pick your language, add a filename, enable line numbers, and highlight specific lines
About this ToolHow it works, benefits & use casesTap to collapse
Wrapping a snippet in a proper Markdown code block is more than adding three backticks — you want the right language tag, sometimes a filename label, and occasionally line numbers or highlighted lines. This formatter does all of it. Paste your code, pick a language from fifteen options (JavaScript, TypeScript, Python, Java, Go, Rust, PHP, Ruby, CSS, HTML, JSON, YAML, Bash, SQL, Markdown), and it emits a fenced ``` block tagged with that language. Choose the indented (4-space) style instead if you prefer. An optional filename is added as an HTML comment above the block, line numbers can be prepended in a padded "N | code" gutter, and you can mark specific lines (entered comma-separated, e.g. 1, 3, 5) with a `// [!code highlight]` annotation that VitePress and similar renderers understand. The output is copy-ready Markdown, shareable via URL, and can pipe into another tool.
How to Use
- 1Choose the Language for your snippet from the dropdown (defaults to JavaScript).
- 2Optionally set a Filename (added as a comment) and a comma-separated list of Highlight lines.
- 3Pick the Code block style — Fenced (```) or Indented (4 spaces).
- 4Toggle Show line numbers if you want a numbered gutter.
- 5Paste your code into the input panel, or click Load example.
- 6Click Format Code Block, then copy, download, or share the resulting Markdown.
Key Benefits
- Fifteen language tags for correct syntax highlighting in renderers
- Fenced (```) or 4-space indented output styles
- Optional filename label added as an HTML comment above the block
- Line numbers in a padded "N | code" gutter when you want them
- Highlight specific lines with the // [!code highlight] annotation
- Settings persist locally; output is copyable, downloadable, and shareable by URL
- Pipe the formatted block straight into another markdown tool
Common Use Cases
- Pasting a snippet into a README or blog post with the correct language fence
- Adding a filename label so readers know which file a code block belongs to
- Marking the key lines of an example with VitePress-style highlight annotations
- Converting an indented code block to a fenced one (or vice versa) for a docs site
- Producing a numbered code listing for a tutorial or step-by-step guide
Formatting options
0 characters
Run to see the formatted code block.
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Fenced style wraps your code in triple-backtick fences with the language tag (```js), which enables syntax highlighting in most renderers. Indented style instead prefixes every line with four spaces — the older Markdown convention that has no language tag. Pick fenced unless a target environment specifically needs indented blocks.
Enter the line numbers to emphasize as a comma-separated list (for example 1, 3, 5). Those lines get a trailing `// [!code highlight]` comment, the convention VitePress and some other docs frameworks read to visually highlight a line. Renderers that do not understand it simply show the comment as text.