How to use the JSON Formatter & Validator
Step 1: Paste your JSON into the input box, or press Load example.
Step 2: Choose an indentation: 2 spaces, 4 spaces or a tab. Tick Sort keys A to Z if you want keys in alphabetical order.
Step 3: Press Format JSON. Or press Minify instead for the smallest single-line version.
Step 4: If the JSON is invalid, read the line and column in the message and fix that spot.
Step 5: Press Copy output, or Download to save a .json file.
Features and benefits
Exact error locations
A strict checker reports the line and column of the first problem, with a plain explanation.
Format or minify
Readable indentation for people, or the smallest form for machines.
Sort keys
Put object keys in alphabetical order at every level, handy for comparing files.
Catches common mistakes
Trailing commas, single quotes, unquoted keys and missing brackets are named explicitly.
Private
Parsing happens in your browser. Your data is not uploaded or stored.
What counts as valid JSON
JSON is stricter than JavaScript object syntax. Keys and strings must use double quotes, there can be no comments, and no comma may follow the last item of an object or array. Values can be strings, numbers, objects, arrays, true, false or null, and nothing else. This tool checks against those rules and tells you the first thing that breaks them.
Limits to know about
Formatting parses the JSON and writes it back out, so formatting differences such as the original spacing are not kept. If an object has the same key twice, only the last one survives, as in any JSON parser. JavaScript stores numbers as 64-bit floating point, so integers beyond about 15 digits may be rounded; the tool warns you when it sees one. Inputs up to two million characters are accepted.
Example use cases
Reading API responses
Make a compressed one-line response easy to read.
Fixing config files
Find the missing comma or bracket in a settings or package file.
Comparing data
Sort keys and format two files so differences are easy to see.
Shrinking payloads
Minify JSON before storing or sending it.
Frequently asked questions
Is my JSON sent to a server?
No. It is parsed and formatted in your browser and is never uploaded.
Why does it say my JSON is invalid?
Usually a trailing comma, single quotes, an unquoted key or a missing bracket. The message gives the line and column of the first problem.
Does it support comments in JSON?
No. Standard JSON has no comments. Remove them before formatting.
Why did a long number change?
JavaScript cannot store integers above about 15 digits exactly. Keep large IDs as strings in your data.
What does sorting keys do?
It puts the keys of every object in alphabetical order. Arrays keep their order.
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Last updated 10 November 2026.