JSON Formatter and Validator

Formats, validates and minifies JSON. Indentation and error detection. For developers. Free.

Free · No sign-up · Runs in your browser · Last reviewed November 2026

Quick demo: how to use this tool

Paste the JSON into the editor.
Press format or validate to check syntax.
Fix bugs noted before using JSON in production.

About JSON Formatter and Validator

Formats, validates and minifies JSON. Indentation and error detection. For developers. Free. JSON Formatter and Validator is a free tool from the Programming and Development category of RoviDev. Speed up your development workflow without leaving the browser. Since everything is processed locally, you can use it with sensitive data with complete peace of mind.

How to use JSON Formatter and Validator

Open JSON Formatter and Validator in RoviDev (you don't need to install anything or register).
Enter the required data in the tool form.
Press the button and see the result instantly on the screen.

JSON formatter and validator: fixing common syntax errors with examples

Paste a JSON string from an API response, config file or log, then format it to read it or validate it to find syntax problems. Minify it when you need the smallest payload. Parsing happens in your browser, so it does not leave your device.

Example of a broken input and its fix:

{'name': 'Ava', "age": 31, "tags": ["a","b",],}

This fails for three reasons: single quotes, a trailing comma inside the array, and a trailing comma before the closing brace. Valid JSON is:

{"name": "Ava", "age": 31, "tags": ["a", "b"]}

Typical US developer uses

Reading a minified REST or webhook payload from Stripe, Shopify or a similar service.
Checking package.json or a VS Code settings file after a manual edit.
Compressing a JSON body before pasting it into a curl command or an environment variable.

Mistakes to avoid

Using single quotes. JSON requires double quotes for keys and strings.
Leaving trailing commas, which JavaScript tolerates but JSON does not.
Putting comments in JSON. The format has none; JSONC and JSON5 do, but strict parsers reject them.
Writing undefined, NaN or unquoted keys. Use null or a string.

Frequently asked questions

Does it format and validate JSON?

Yes. It embellishes (indents) the JSON to read it better and alerts you if there are syntax errors indicating where the problem is.

Can I minify JSON for production?

Yes. In addition to formatting, you can compact it by removing spaces and line breaks to reduce its size.

Is my JSON data uploaded anywhere?

No. All processing is local in your browser; ideal for JSON with sensitive information.

Why does my JSON fail when it works in JavaScript code?

A JavaScript object literal allows single quotes, unquoted keys and trailing commas. JSON is stricter: double quotes only and no trailing commas.

Does formatting change the data?

No. Formatting only adds or removes whitespace and line breaks. Keys, values and their order stay the same.