Skip to content

Free developer tool · runs in your browser

JSON formatter, validator & minifier.

Beautify messy JSON, catch syntax errors with exact positions, or minify to reduce file size. Everything runs locally in your browser. Your data is never uploaded, so it is safe for API keys, configs and production payloads.

Mode
Indent
Indent
Input JSONempty
OutputWaiting for input
Input size
0 chars · 0 B
Output size
0 chars · 0 B
Saved
–
Structure
–

Privacy: this tool is fully client-side. Your JSON never leaves your browser: no uploads, no logging, no size limits beyond your device memory.

What this tool does

Format, validate and minify, in the browser.

  • 01

    Format & beautify JSON

    Turn single-line or messy JSON into a readable, indented structure with 2 spaces, 4 spaces or tabs. Useful for reviewing API responses, config files and logs.

  • 02

    Validate with exact errors

    Invalid JSON? The validator pinpoints the error with line and column numbers: trailing commas, missing quotes, unescaped characters, so you can fix it in seconds.

  • 03

    Minify & reduce file size

    Strip whitespace to compress JSON for production payloads and configs. The size badge shows exactly how many bytes and what percentage you saved.

FAQs · JSON formatter

JSON formatting · frequently asked questions

Privacy, size limits, common syntax errors and what minifying actually changes.

No. The tool is entirely client-side: parsing, formatting and minifying all happen in your browser. Nothing is sent to a server, logged or stored, so it is safe for API keys, configs and production payloads.
There is no artificial limit. The only constraint is your device memory. Multi-megabyte payloads work fine on a normal laptop.
The usual culprits are a trailing comma, single quotes instead of double, an unescaped newline inside a string, or a stray BOM at the start. The error message gives the exact position so you can jump straight to it.
No. Minifying only removes insignificant whitespace between tokens. Keys, values, ordering and types are identical. The parsed result is byte-for-byte equivalent.
Not directly. This validates strict JSON as specified in RFC 8259, so comments, trailing commas and unquoted keys are rejected by design.
Paste your JSON into the input, choose Minify / compress, and the output appears at once with every space, tab and line break between tokens removed. Copy output or Download .json takes the result. It all runs in your browser, so nothing is uploaded.
It depends on how the file was indented: deeply nested JSON formatted with 4 spaces or tabs shrinks the most, and JSON that is already on one line barely changes. The Saved figure under the output shows the exact bytes and percentage for your file.
Minifying removes whitespace only. For larger savings, serve JSON with gzip or Brotli compression, drop fields the client never reads, leave out null or default values, and paginate large lists instead of sending them in one response.

Next step

Working with APIs all day?

QalbIT designs and builds production-grade REST APIs, backends and integrations for web and mobile products, the systems behind the JSON.

Backend & API development

Keep exploring

More free tools

More free tools

Each one opens on a worked example and shows its answer without a signup.

All free tools

Further reading