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JSON Formatter & Validator
Paste any JSON to instantly format it with readable indentation or minify it to one line. Syntax errors show the exact line and column. 100% in-browser — nothing leaves your device.
All formatting runs in your browser using
JSON.parse() + JSON.stringify(). Your data is never uploaded or stored.
About JSON Formatter & Validator
JSON Formatter & Validator reads any JSON string — raw, minified, hand-written, or copied from a terminal — and outputs properly indented, human-readable text. Paste the input, click Format, and every key-value pair appears at the correct indent level, with nested objects and arrays indented one step deeper than their parents.
Three modes are available from the same interface. Format adds 2-space indentation and writes every bracket and brace on its own line. Minify reverses that: it strips all whitespace, newlines, and indentation to produce the smallest valid JSON string. Validate runs during both operations — if the input has a syntax error, the exact line and column of the first violation appear before anything else runs.
Validation is exact because it uses the real parser. Both formatting and validation run in your browser using the JavaScript runtime's native JSON.parse() — the same parser running in Chrome, Firefox, Safari, and Node.js. When JSON.parse() fails, it returns the exact offset of the first error. There is no secondary parser approximating the position. If your JSON fails in this tool, it will fail identically in every JavaScript environment.
No JSON leaves your browser. Nothing is sent to any server. This matters when the input contains credentials, API keys, session tokens, database records, or any data subject to privacy requirements. Pasting into this formatter carries the same risk profile as opening the file in a text editor. The output stays in the tab; closing the tab removes every trace.
The formatter handles all six standard JSON data types: objects ({}), arrays ([]), strings (including Unicode and emoji), numbers (integers and floats), booleans, and null. It does not handle JSON5 (which allows comments and trailing commas), JSONC (JSON with comments used in some VS Code configuration files), or NDJSON (newline-delimited JSON where each line is a separate JSON object). Those formats require a different parser; pasting them here produces a syntax error at the first comment or trailing comma.
For large inputs — API exports, database snapshots, structured log files — the formatter works in-browser up to available tab memory. Inputs in the tens of megabytes process without issue. No per-file limit is enforced.
Common use cases
- API response debugging — A backend developer gets a 401 back from a payment gateway with a response body that is 800 characters of minified JSON. Paste it here: the error code, message, and trace fields are readable in the first scroll instead of a hunt through raw text.
- Pre-deployment JSON validation — A DevOps engineer has a Terraform variable file (terraform.tfvars.json) that fails terraform validate with no clear reason. Paste it here: the exact line and column of the comma error appear immediately, without running Terraform locally.
- Config file cleanup — A frontend developer inherits a project's tsconfig.json that has been edited by multiple people with inconsistent indentation. Paste, format, copy back. The output is canonical 2-space-indented JSON that reads clearly and diffs cleanly in code review.
- Webhook payload inspection — A QA engineer receives a Stripe webhook event from a staging environment and needs to confirm that the metadata object contains the expected fields before marking an integration test as passing. Formatting the payload makes the check a scan rather than a line-by-line parse.
- Building JSON for API requests — A data analyst is constructing a complex POST body for a Salesforce bulk API call. They draft it in the formatter — where structural errors show on every keystroke — confirm the output is valid, then minify before pasting into Postman.
Frequently asked questions
What is a JSON formatter?
A JSON formatter takes compact or inconsistently indented JSON and outputs it with consistent 2-space indentation, one key-value pair per line, brackets at the correct nesting level. This makes the data structure readable at a glance and easier to scan for unexpected fields or missing values.
Why should I validate JSON before using it?
JSON syntax is strict — a single trailing comma after the last item in an array or object causes every JSON parser to fail, in every language. Validating before use catches these errors before they reach production code, a CI pipeline, or an API endpoint.
What is the difference between JSON and JSONC?
Standard JSON (RFC 8259) allows no comments. JSONC adds // and /* */ comments, which VS Code uses internally for files like settings.json and keybindings.json. JSONC is not valid JSON — JSON.parse() fails at the first comment character. If you paste a VS Code config file and see a parse error on the // line, that is why.
Can I format JSON that has trailing commas?
No. Trailing commas after the last item in an object or array are valid in JavaScript and JSON5, but not in standard JSON. The validator reports an error at the trailing comma. Remove trailing commas first, then format.
Is my JSON data sent to a server?
No. Formatting and validation run entirely in your browser using the native JavaScript JSON.parse() and JSON.stringify() functions. Nothing is uploaded, transmitted, or stored anywhere.
Does the formatter handle Unicode and emoji?
Yes. JSON strings are Unicode by specification (RFC 8259 section 8.1). Emoji, non-ASCII characters, and 4-byte code points all round-trip correctly through JSON.parse() and JSON.stringify() without modification.
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