JSON Formatter & Validator

What is JSON?

JSON — JavaScript Object Notation — is the standard way apps, websites and APIs share data. When you open a weather app, check a bank balance or load a YouTube page, the server usually sends the data as JSON: a plain-text format of keys and values inside curly braces { } for objects and square brackets [ ] for lists. A value can be a string in double quotes, a number, true or false, null, another object or an array. For example, {"name":"Anees","city":"Abbottabad","followers":1200,"verified":true} is a JSON object with four keys. Because JSON is just text, it works in every programming language — Python, JavaScript, PHP, Java and more — which is why developers use it everywhere, from mobile apps to cloud servers.

How to use the JSON Formatter

Formatting JSON takes four steps. Step 1: paste your JSON into the input box — an API response, a config file, a settings file or a data export — or click "Load sample JSON" to try an example. Step 2: choose the indent: 2 spaces is the most common style, 4 spaces is easier to read for deeply nested data, and Tab matches many code editors. Step 3: click "Format JSON". If your JSON is valid, the beautified result appears below with a green "Valid JSON" message and counts of lines, characters and keys. Step 4: copy the result with "Copy output" or save it with "Download .json". The "Minify" button squeezes the same JSON into a single line, and "Validate" checks it without changing it.

Common JSON errors and how to fix them

Most JSON errors come from four small mistakes. 1. Trailing comma: {"name":"Anees",} has a comma after the last item — remove it; JSON never allows a comma before a closing brace. 2. Unquoted keys: {name:"Anees"} is invalid — every key must be in double quotes: {"name":"Anees"}. 3. Single quotes: {'name':'Anees'} is invalid in JSON — strings and keys must use double quotes, even though JavaScript allows single quotes. 4. Missing comma: {"name":"Anees" "city":"Abbottabad"} needs a comma between the two items. This tool shows the exact line and column of the error, and the offending line itself, so you can fix it in seconds instead of searching a 500-line file by hand.

Example: before and after

An API returns one long line: {"name":"Anees","city":"Abbottabad","skills":["web","design"],"followers":1200,"verified":true}. It is valid, but unreadable. After formatting with 2-space indent it becomes a clear list: name, city, skills (an array of two items), followers and verified — 5 keys, easy to read, easy to edit. Minify does the reverse: it turns a long, spaced-out file into one compact line, which is what you send to a server.

Tips and common mistakes

• Always validate an API response before using it in code. One missing bracket in a response can break a whole app — paste it here first and fix the error before you code against it.
• Minify before sending over slow mobile data. Removing spaces and line breaks can shrink a large JSON file by 20–30%, which makes uploads and API calls faster.
• Check the brackets match. Every opening { needs a closing }, and every [ needs a ]. Most "Unexpected token" errors are a bracket that was never closed.
• Numbers have no quotes. 1200 is a number; "1200" is a string. Mixing them up breaks sorting and maths in code.
• Never paste passwords or secret API keys into any online formatter. This tool never uploads your JSON — everything runs in your browser — but the rule still stands for every other site.