How the JSON formatter works
This tool parses your input with the browser's built-in JSON.parse, then re-serializes it with JSON.stringify using the indentation level you choose. If parsing succeeds you get clean, consistently indented output; if it fails you see the exact character position where the syntax broke down.
Because the operation is parse-then-serialize, the formatter also implicitly validates your JSON. Trailing commas, single-quoted strings, and unquoted keys will all surface as parse errors with a line and column reference.
Choosing an indentation level
Two-space indent is the most common convention in JavaScript and TypeScript projects, and produces compact output that still scans well. Four spaces is favoured in Python ecosystems and configuration files where deep nesting is rare. Eight spaces is unusual but can help when you need extreme visual separation between levels during debugging.
The choice has no effect on the data itself. JSON parsers ignore whitespace between tokens, so a 2-space file and a 4-space file are semantically identical. Pick whichever matches your project's .editorconfig or team style guide.
Privacy and security
The entire formatting operation runs in your browser tab using JavaScript's native JSON methods. Your input is never transmitted to any server, stored in any database, or logged anywhere. This makes the tool safe for production payloads, API responses containing tokens, and internal configuration files.
If you close or refresh the tab, the data is gone. There is no backend, no analytics on input content, and no cookie tracking what you paste.
Common pitfalls and tips
Trailing commas after the last element in an array or object are valid in JavaScript but not in JSON. If you copy an object literal from source code, strip any trailing commas before formatting. Similarly, single quotes and comments (// or /* */) are not part of the JSON specification and will cause a parse error.
If you are working with very large files (tens of megabytes), performance depends on your browser's JS engine. Chrome and Edge handle files up to roughly 50 MB without issues; beyond that, consider a streaming CLI tool like jq.
Frequently asked questions
Is my JSON uploaded anywhere?
No. Parsing and formatting happen entirely in your browser using JSON.parse and JSON.stringify. Nothing is sent over the network.
Does the formatter handle comments in JSON?
No. Comments are not part of the JSON specification. If your input contains // or /* */ comments, the parser will report a syntax error. Strip comments first or use a JSONC-aware tool.
What happens if my JSON has trailing commas?
The formatter will report a parse error at the position of the trailing comma. Trailing commas are valid in JavaScript object literals but are not allowed in strict JSON.
What is the maximum file size I can format?
There is no hard limit imposed by the tool. Practical limits depend on your browser and available RAM. Most modern browsers handle files up to 50 MB comfortably.
Does formatting change the meaning of my JSON?
No. Formatting only adds or adjusts whitespace between tokens. The parsed data structure is identical before and after formatting.