About the JSON Viewer
A JSON viewer for reading, validating and comparing JSON documents directly in the browser. Paste an API response or log payload to pretty-print it, walk the structure in a collapsible tree, or open two documents side by side to see exactly what changed. Parsing happens locally, so production payloads and access tokens never leave your machine.
How to use the JSON Viewer
-
Paste or open your JSON
Drop raw JSON into the editor. Invalid syntax is flagged immediately with the position of the offending character, so malformed API responses are easy to pinpoint.
-
Format, minify or explore the tree
Pretty-print with consistent indentation, minify to strip whitespace before sending, or switch to the tree view to collapse and expand nested objects and arrays.
-
Compare two documents
Open a second tab and switch to diff mode to see added, removed and changed keys highlighted side by side — useful for spotting what an API changed between two calls.
When to use it
Debugging API responses
Turn a single-line response body into readable, indented JSON and find the field that is missing or the wrong type.
Reviewing config changes
Diff two versions of a configuration file to confirm exactly which keys a deployment altered.
Validating before submitting
Confirm a request body parses cleanly and minify it before pasting into a client or test fixture.
Frequently asked questions
Is my JSON uploaded to a server?
No. Parsing, formatting and diffing all run in your browser using the native JSON parser. Nothing is transmitted, which makes it safe for payloads that contain tokens or customer data.
What is the maximum file size?
There is no hard limit imposed by the tool — the practical ceiling is your browser memory. Documents in the low megabytes format instantly; very large files may take a moment to render in tree view.
Can I compare two JSON files?
Yes. The diff mode compares two documents structurally rather than as plain text, so key reordering does not produce false differences.
Does it support JSON with comments or trailing commas?
No. The tool validates against the strict JSON specification, so JSONC and JSON5 extensions are reported as syntax errors. This is intentional — it catches files that would be rejected by a strict parser downstream.
Why does my JSON show an error when it looks correct?
The most common causes are single quotes instead of double quotes, a trailing comma after the last element, or unescaped control characters pasted from a terminal. The error message reports the character position to help locate it.
Related tools
Browse all free online tools on Tooly — every one runs in your browser, with no account required.