JSON Formatter
Format, validate and minify JSON data online
What is JSON Formatter & Validator?
JSON (JavaScript Object Notation) is the most widely used data interchange format in modern web development. APIs return JSON; configuration files use JSON; databases store JSON; mobile apps exchange JSON. When working with raw JSON — from API responses, logs, or configuration files — the data is often minified (compressed into a single line without whitespace) to save bandwidth, making it extremely difficult to read and debug.
A JSON formatter (also called a JSON beautifier or JSON pretty-printer) takes minified or poorly formatted JSON and adds proper indentation, line breaks, and spacing to make the structure immediately readable. A JSON validator checks that the syntax is correct — verifying that all brackets are closed, keys are quoted, values are valid data types, and there are no trailing commas or other common errors.
Altairys's JSON Formatter and Validator does both — it formats your JSON with configurable indentation (2 or 4 spaces, or tabs), validates syntax and highlights errors with the line and character position, allows you to toggle between formatted and minified views, and provides a tree view for exploring nested structures. This tool is indispensable for backend developers debugging API responses, frontend developers working with configuration files, and DevOps engineers reading log output.
How to Use JSON Formatter & Validator
- Paste your JSON
Paste raw, minified, or malformed JSON into the input editor.
- Validate and format
Click Format — the tool validates syntax and adds proper indentation and line breaks.
- Browse the structure
Use the tree view to explore nested objects and arrays interactively.
- Copy or minify
Copy the formatted JSON or switch to minified view to compress it back for production use.
Key Benefits
Syntax errors are highlighted immediately with exact line and column information.
Navigate complex nested JSON structures with a collapsible tree view.
Switch between human-readable and minified JSON with one click.
JSON is processed locally — safe for API keys, tokens, and private data.
Frequently Asked Questions
Common causes: trailing commas after the last element (invalid in JSON), single quotes instead of double quotes, unquoted keys, undefined or NaN values (not valid JSON), or unclosed brackets.
JSON is a text format and a subset of JavaScript. All JSON is valid JavaScript, but not all JavaScript objects are valid JSON — JavaScript allows single quotes, comments, and trailing commas; JSON does not.
Yes. Since processing is in-browser, the practical limit is your device's RAM. Most devices handle JSON files up to several MB without issues.
After pasting and formatting your JSON, click the Minify button to remove all whitespace and compress it to a single line — ready for API responses or config files.
No. All formatting and validation is performed in your browser using JavaScript. Your data — including any API keys or credentials in the JSON — never leaves your device.