What is HTML / CSS / JavaScript Formatter?
HTML, CSS, and JavaScript Formatter uses the matching Prettier parser to reprint compact, uneven, or inconsistent code in a stable layout. It supports two- or four-space indentation and a JavaScript semicolon option. Input is parsed and printed as source text only; it is never rendered as a page or executed as script. Common workflows include the following. Clean frontend snippets copied from logs, APIs, or build output. Standardize HTML, CSS, and JavaScript layout before review. Use explicit parser errors to locate malformed brackets, tags, or declarations. The page also documents input boundaries, output behavior, and practical cautions so you can review the result before putting it into an application, configuration, test, or production workflow.
When to use it
- Clean frontend snippets copied from logs, APIs, or build output.
- Standardize HTML, CSS, and JavaScript layout before review.
- Use explicit parser errors to locate malformed brackets, tags, or declarations.
How to use it
- Choose HTML, CSS, or JavaScript.
- Paste code and set indentation and semicolon preferences.
- Format, review parser errors, and copy the result.
- Load one of the realistic examples first to verify the selected options and processing direction before replacing it with your own data.
- Review the output, status message, and documented limits; copy, download, or continue only after the result matches your expectation.
Runnable examples
The “Example 1” and “Example 2” buttons load the matching inputs. They cover different structures, directions, or boundaries and can be run directly in the workspace.
Example 1
const release={site:'JSONLane',tools:[21,22,23],checks:{unit:true,e2e:true}};console.log(release)Example 2
<main><section class="tools"><h1>JSONLane</h1><p>Local tools</p></section></main>Input rules
- Select the parser that matches the HTML, CSS, or JavaScript input.
- Input must parse in that language; template dialects and vendor extensions may fail.
- The character limit is checked before formatting and source code is never executed.
- Text input is counted before processing and is limited to 500,000 characters on this page; file modes apply the separate file limit shown in the workspace.
- Input must parse in the selected language.
Output rules
- Prettier prints from a syntax tree rather than simply inserting spaces.
- Indent width and JavaScript semicolons follow the selected options; other choices use parser defaults.
- Comments generally remain but may move, and successful formatting does not prove correctness or safety.
- Output reflects only the current input, direction, and options; rerun after changing a mode or value instead of treating an earlier result as current.
- Comments generally remain but can move.
Limitations and cautions
- Input must parse in the selected language.
- Comments generally remain but can move.
- Formatting does not prove that code is correct or safe.
How your data is handled
Source text and the bundled Prettier parser run in the current browser. Nothing is uploaded, executed, resolved from dependencies, or written to project files.