What is JSON Viewer?
A JSON viewer is a tool that takes raw JSON text and renders it in a readable form — indented, syntax-highlighted, and navigable. This one validates as you type, reports the exact line and column of a syntax error, and lets you switch between formatted code, a collapsible tree, and a table view of arrays.
It runs entirely in your browser. The JSON you paste is parsed by your own device and is never uploaded to a server, which means you can safely inspect API responses that contain tokens, customer records, or anything else you would not paste into a hosted service.
JSON is a text format that facilitates structured data interchange between all programming languages.
Features
- Real-time validation
- Every keystroke is parsed. When JSON is invalid you get the parser's message along with the position, so you can jump straight to the missing comma or unquoted key instead of hunting for it.
- Three ways to read the same data
- Code view for formatted JSON, tree view for structure you can fold and unfold, and table view that turns an array of objects into rows and columns with pagination.
- Format and minify
- Pretty-print JSON with consistent indentation for reading, or strip every unnecessary byte for a config file, a query string, or an HTTP body.
- Built for large payloads
- Tree view renders the first 100 items of a collection and expands on demand, and the table view paginates, so a multi-megabyte API response does not freeze the page.
- File upload and clipboard
- Open a .json file up to 10 MB from disk, or copy the formatted result back to your clipboard in one click.
How to use
- 1
Paste your JSON
Paste or type JSON into the editor on the left, or upload a .json file from your computer.
- 2
Check that it is valid
The status bar reports whether the JSON parses. If it does not, it shows the error message and the position where parsing stopped.
- 3
Format or minify
Use Format to pretty-print with indentation, or Minify to collapse the document to a single line.
- 4
Explore the structure
Switch the right panel to tree view to fold and unfold nested objects, or to table view to read an array of objects as rows.
- 5
Copy the result
Copy the formatted JSON back to your clipboard when you are done.
Large integers lose precision, silently
JSON.parse turns every number into a JavaScript double, which holds integers exactly only up to 2^53 − 1 (9,007,199,254,740,991). A Twitter-style 64-bit ID such as 9007199254740993 parses to 9007199254740992 — off by one, with no error and no warning. The same happens to Snowflake IDs, Kafka offsets, and any bigint column serialised as a JSON number.
The viewer shows what the parser produced, so a value that changed on the way in will differ from the raw text you pasted. If you see that, the fix is on the producing side: serialise large identifiers as JSON strings. RFC 8259 §6 explicitly warns that interoperability is only assured within the double-precision range, which is why every API that survived this problem now sends IDs as strings.
Frequently asked questions
Is my JSON uploaded anywhere?
No. The tool is a static page with no backend that receives your content. Parsing, formatting, and validation all happen in JavaScript on your own device, so the JSON you paste never leaves your browser.
Is this JSON viewer free?
Yes, it is free to use with no account and no usage limit. The site is supported by ads.
What is the largest file I can open?
File upload accepts .json files up to 10 MB. Pasting is limited only by your browser's memory — the tree and table views page through large collections so the page stays responsive.
Why does my JSON say it is invalid when it looks fine?
The most common causes are trailing commas after the last element, single quotes instead of double quotes, unquoted object keys, and comments — none of which JSON allows, even though JavaScript object literals and JSON5 do. The error message shows the position where parsing stopped.
What is the difference between formatting and minifying JSON?
Formatting (also called pretty-printing or beautifying) adds line breaks and indentation so a human can read the structure. Minifying removes every space and line break that the parser does not need, producing the smallest valid document — useful for config values, query parameters, and request bodies.
Can I view a JSON array as a table?
Yes. When the document is an array of objects, the table view derives the columns from the object keys and shows one row per element, with pagination at 100 rows per page. A single object is shown as a key-value table instead.
Does it work offline?
Once the page has loaded, formatting and validation keep working without a network connection, because all the work is done by JavaScript already running in your browser.
If you hit this
- Why does my JSON parser fail on a file full of valid JSON?JSON, JSONL, and NDJSON are not the same file
- Should an ID be a JSON number or a JSON string?Why an ID should be a string in JSON
- How do I know whether a Unix timestamp is in seconds or milliseconds?Telling seconds from milliseconds in a timestamp
- Is it safe to paste a production token into an online tool?What a browser-only tool does and does not protect
Specifications this follows
- RFC 8259 — The JavaScript Object Notation (JSON) Data Interchange Format — The current JSON standard. Defines why trailing commas, comments, and single quotes are rejected.
- ECMA-404 — The JSON Data Interchange Syntax — The syntax half of the same specification, maintained in parallel with RFC 8259.
- MDN — JSON.parse() — The parser this tool uses, including the exact error positions it reports.
Related tools
- CSV Viewer & ConverterOpen delimited data as a table, guess the delimiter, and convert it to JSON.
- JWT DecoderSplit a JSON Web Token into header, claims, and signature — with expiry read as a real time.
- YAML ↔ JSON ConverterConvert YAML to JSON and back, with the parser's own error position when it will not parse.