Validate JavaScript Syntax

Spot syntax errors in your JS before you ship.

Processed locally — nothing is uploaded

Input

Output

About Code Formatter

Useful for making a minified payload readable again, for checking that a config parses before you ship it, or for stripping a file down for production. Switching language keeps whatever you have already pasted.

Check a snippet of JavaScript for syntax errors before you ship it — the linter flags the exact line where parsing fails. All checking is done locally in your browser.

Paste messy or minified code and instantly beautify, minify or validate JSON, HTML, CSS, SQL, XML and YAML. Beautifying re-indents your source with consistent spacing so it is easy to read and review; minifying strips whitespace and comments to ship smaller files; validating surfaces syntax errors with the exact location so you can fix them fast.

It also doubles as a converter between common data formats — JSON to CSV, CSV to JSON, YAML to JSON and back — which is handy when wiring up APIs, configs or spreadsheets. Converting is where structure mismatches surface: CSV has no nesting, so a nested JSON object has to be flattened or dropped.

Learn how this works

A Practical Guide to Everyday Developer Encoding & FormattingHow and when to use Base64, JSON formatting, hashing, JWTs, regex and cron — with free in-browser tools for each task.11 min read

Frequently asked questions

Does this find bugs in my code?

No — it finds syntax errors, which is a narrower thing. It tells you the code cannot be parsed and where parsing stopped. Logic errors, type mistakes and runtime failures all parse perfectly well and need a linter, a type checker or tests.

Why is the reported line different from where the real problem is?

A parser only fails once it reaches something that cannot follow what came before, so an unclosed brace or a missing bracket is typically reported some distance below its actual cause. Read upward from the reported line to the last construct you opened.

Is my code sent anywhere to be checked?

No. Parsing happens in your browser and the code is never executed or uploaded, so it is safe to check a snippet containing internal logic or configuration.

Pro Tips

→Paste unformatted JSON, HTML, CSS, or SQL code and apply consistent indentation (2, 4, or tab spaces) in one click.
→Use minification toggle to reduce code size by 30-50% for production deployment or email constraints.
→Export formatted code directly to clipboard to paste into documentation, emails, or config files instantly.
→Compare formatted vs minified side-by-side to verify code compression doesn't break syntax.

Common Use Cases

•Checking a snippet before pasting it into a production console or template
•Finding the unbalanced brace in a file your editor has stopped highlighting correctly
•Verifying generated or concatenated JavaScript actually parses

How It Compares

While Prettier and VS Code extensions require installation and configuration, our web-based formatter works instantly on any device without setup, offering broader language support (HTML, CSS, SQL) in a single tool compared to language-specific formatters like Beautifier.io.

More Code Formatter tools

Code Formatter JSON to CSV Converter CSV to JSON Converter CSS Minifier JavaScript Unminifier SQL Prettifier XML Beautifier YAML to JSON Converter JSON to YAML Converter Validate JSON Online