JSON Formatter & Beautifier
Paste compact or hard-to-read JSON and format it with consistent indentation before sharing it, reviewing an API response, or committing a fixture.
- Choose two spaces, four spaces, or tabs to match your project.
- Invalid JSON is reported instead of silently changed.
- Copy or download the formatted result when you are finished.
This tool runs entirely in your browser. Your JSON is not uploaded, stored, or logged.
When to format JSON
Minified JSON is fine for machines and terrible for humans. Format a payload when you need to review nesting, spot missing fields, prepare a code review fixture, or compare two responses by eye before running a diff.
Formatting does not change the data model. It only changes whitespace so objects, arrays, and nested keys are readable. If the input is invalid, fix the syntax first with the validator — a formatter cannot invent missing quotes or remove trailing commas for you.
A practical debugging workflow
Validate first, format second, then decide what to do next. Once the document is valid and readable, you can minify it for a compact env value, convert a sample into TypeScript types, or run a JSONPath query against a nested response.
- Paste the raw API body or config file into the editor.
- Confirm the document is valid JSON (the tool will say so if it is not).
- Pick the indentation your project already uses.
- Copy or download the result into your PR, ticket, or local fixture.
Privacy: why local formatting matters
API payloads often include emails, internal IDs, auth tokens, or customer fields. Uploading that to a random online formatter is an unnecessary risk. This tool runs entirely in your browser — the JSON never leaves your device.
Two things formatting quietly drops
Because a formatter parses the document into an object and prints it back, it can only preserve what JSON itself can represent. Two lossless-looking values do not survive that round trip.
Duplicate keys are the first. JSON allows the same key twice — {"a": 1, "a": 2} — and JSON.parse, like most parsers, keeps the last one (the spec leaves this implementation-defined, and a few parsers reject duplicates outright). So this formatter silently reduces a duplicated key to one value, and a validator will not flag it because the syntax is legal. If duplicates matter, deduplicate before trusting the output.
Large integers are the second. JavaScript numbers are IEEE-754 doubles, exact only up to 2^53-1 (Number.MAX_SAFE_INTEGER, 9007199254740991). A tweet ID, a Snowflake ID, or a 64-bit database key in a pasted response can be rounded on the way through, and the formatted output is confidently wrong. When the source uses IDs beyond that range, treat them as strings — JSON has no integer type of its own.
Key order and readable diffs
JSON object keys are unordered by definition, but the order they appear in a file is real and it is what a reviewer reads. When two services serialize the same object, the field order can differ, and a line-based diff then marks the whole object as changed even though nothing did.
Formatting preserves the order of ordinary string keys, but not every key: JavaScript emits integer-like keys in ascending numeric order, so an object that listed "10" before "2" is reprinted as "2" then "10". Read that as a reordering, not a value change. For string keys, formatting keeps the existing order and makes it visible, which is the first step — if a noisy diff keeps coming back, sort keys at the serializer, not in the pasted document.
Frequently asked questions
Does formatting change my JSON data?
Mostly no. Formatting only adjusts whitespace and indentation — but two things do not survive the parse-and-reserialize. A duplicate key collapses to its last value, and an integer past 2^53-1 is rounded. If the input is invalid JSON, the tool reports an error instead of guessing a repair.
What indentation should I use?
Match the project. Many JavaScript and TypeScript codebases use two spaces; some configs and Go-adjacent tooling prefer tabs. Consistency matters more than the specific choice.
Is my JSON uploaded when I format it here?
No. Parsing and pretty-printing run in your browser with client-side JavaScript. Nothing is sent to a server for formatting.
Why did a long number change when I formatted it?
It exceeded JavaScript's safe integer range (2^53-1), so the parser rounded it. IDs from Twitter/X, Snowflake, and 64-bit database keys are the usual culprits — keep them as strings if they must survive round-tripping.
Can I format very large JSON files?
Up to what your browser's memory allows. A formatter parses the whole document at once; multi-hundred-megabyte files are better handled with a streaming parser or jq on the command line.