Validate JSON Online

Catch syntax errors and lint your JSON instantly — nothing is uploaded.

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.

Paste JSON to instantly check it for syntax errors — the validator pinpoints the first problem, such as a trailing comma, an unquoted key or an unbalanced bracket, so you can fix it fast. Nothing is uploaded; validation runs 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

What does the validator actually check?

Syntax — that the document parses as JSON. It reports the first position where parsing fails, which is where the classic culprits show up: a trailing comma, a single-quoted string, an unquoted key or an unbalanced bracket. It does not check your data against a JSON Schema.

My JSON looks fine but still fails. What should I look for?

Usually an invisible character. A smart quote pasted from a document, a non-breaking space, or a byte-order mark at the start of a file will all break parsing while looking perfectly normal. Retyping the reported line by hand often fixes it instantly.

Is trailing-comma JSON valid?

Not in standard JSON — `{"a": 1,}` is invalid, even though JavaScript object literals allow it and some parsers accept it as an extension. If a trailing comma is what broke your file, that mismatch is usually the reason.

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

•Finding the exact character that made a config file fail to load at startup
•Checking a hand-edited fixture or seed file before committing it
•Confirming a webhook payload is well-formed before blaming the sender

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 JavaScript Syntax