JSON formatter / validator
Paste a blob of JSON and the tool validates it (with the exact position of any error), indents it cleanly, or minifies it to one line. A missing comma or a trailing one is the usual culprit when a payload refuses to parse. The payload never leaves your browser, which matters when it holds secrets or personal data.
- 100% local
- Free · no account
- Instant result
This tool runs entirely in your browser — nothing is sent to a server.
JSON is the most widespread data exchange format, but minified or badly indented JSON is unreadable, and a single stray comma makes it invalid. This tool validates your JSON, locates the error (line and column) and reformats it with clean indentation — or minifies it to reduce its size.
Everything happens in your browser: you can paste sensitive data (configurations, API payloads) without it being transmitted anywhere.
How it works
Type the figures or drop the file you want to process — the tool checks them as you go.
Everything is computed directly in your browser. Nothing is sent to a server.
The result appears instantly, with the detailed breakdown ready to copy, download or keep.
Why use this tool
No account, no download, no limit: the result appears as soon as you enter your data.
Every rule, algorithm and check reflects what we use ourselves every day at Flexina.
The calculations follow the official standards, and the step-by-step detail lets you double-check the outcome.
What does running it locally bring you?
Files, figures and documents never leave your device: nothing is stored, nothing is sent.
Once the page is loaded, you can cut the network: the tool keeps working.
No upload, no account, no third-party server in between: results stay fast and fully private.
Frequently asked questions
Why is my JSON invalid?
Classic causes: a comma after the last element, single quotes instead of double quotes, unquoted keys, comments (forbidden in JSON). The error message gives the exact position of the problem.
Format or minify, when to choose which?
Format to read and debug; minify to transmit or store (removes spaces and line breaks, without changing the data).
Is my data sent anywhere?
No, validation uses your browser’s JSON parser, locally. Nothing leaves your machine.