How to Format JSON Online
JSON (JavaScript Object Notation) is the standard data format used by web APIs, configuration files and databases. Because it is usually produced by machines, JSON often arrives as a single dense line that is painful to read, debug or edit by hand. Formatting, also called "pretty-printing", re-indents that data and breaks it across multiple lines, giving you the clear, human-friendly structure you are used to seeing in browser developer tools and modern code editors.
The most common problems when working with JSON are unreadable minified output and syntax errors caused by a misplaced comma, quote or bracket. A dedicated formatter solves both at once: it beautifies the structure instantly and validates the document in the same pass, pointing you to the exact line and column of any mistake. That turns a frustrating search through a wall of text into a one-second fix.
Unlike desktop tools that require installation, or online services that ask you to upload sensitive data to their servers, this formatter runs entirely in your browser. You paste, you read, you fix — and your data never leaves your device. It works equally well for API responses, config files, test fixtures and any JSON snippet you copy from your editor or terminal.
Once the document is valid and readable, the next question is usually what changed between two versions. JSON Compare & Diff reports every added, removed and changed value with its full path, and it uses the same parser as this formatter, so a document that validates here will compare cleanly there. If a payload contains a token, JWT Decoder shows its header and claims without sending it anywhere, and Base64 Encoder & Decoder handles the encoded blobs that tend to sit beside them.
How to Use This Tool
- Paste your JSON into the input area on the left. The tool starts validating the moment you type.
- Choose a mode — click "Format" for a pretty, indented layout and pick 2 or 4 space indentation, or click "Minify" to compress the output to a single line.
- Read the result on the right. If your JSON has a problem, a clear error message tells you the exact line and column to check.
- Copy the output with one click and drop it back into your code, request body or config file.
Benefits
- Real-time validation — errors are reported instantly with their exact location.
- Instant formatting — switch between pretty and minified output without reloading the page.
- 100% private — everything runs locally in your browser; nothing is uploaded.
- Copy-ready — grab the formatted or minified result with a single click.
- Free forever — no signup, no limits and no watermarks.
Validation happens in the same place: if your JSON will not parse, a clear error message tells you the exact line and column to check, so you can fix it and beautify the result without leaving this page.