How to Validate JSON in Your Browser
Paste your JSON into the input box
Drop in a raw API response, a config file, or any JSON snippet. The text is read straight from the input field, so nothing is uploaded. Validation runs as you type, so you do not have to wait to see whether the syntax holds.
Read the validity badge and structure summary
A green Valid JSON badge appears when the native browser parser accepts your text, followed by a short summary of the top level: the number of object keys (with the first five named) or the number of array items. Strings are previewed up to 40 characters so you can confirm you pasted the right payload.
Fix errors or clear and retry
If the parser rejects the text, a red Invalid JSON badge shows the exact error message from the browser, including the character position where parsing stopped. Correct that spot, or press Clear to empty the field and start fresh.
What Counts as Valid JSON
This validator uses the browser native JSON parser, which follows the strict JSON specification. Many things that look fine in JavaScript or YAML are rejected. The table below shows common patterns and whether the parser accepts them.
| Pattern | Example | Result |
|---|---|---|
| Double-quoted keys and strings | {"name": "value"} | Valid |
| Single quotes | {'name': 'value'} | Invalid |
| Trailing comma | {"a": 1} | Invalid |
| Comments | {"a": 1} // note | Invalid |
| Unquoted keys | {name: "value"} | Invalid |
| Top-level value | "just a string" or 42 | Valid |
When to Use This Validator
Checking an API response
Paste the body returned by an external service to confirm it is well-formed JSON before your code tries to parse it. The structure summary tells you at a glance whether you received an object, an array, or a bare value.
Reviewing a config file
A single stray comma or missing quote can break a JSON configuration silently. Validate the file here first so the error position points you to the exact character to fix.
Inspecting unknown payloads
When you are not sure what a snippet contains, the summary lists the top-level key names and counts, giving you a quick map of the data without scrolling through the whole document.
Sensitive or local data
Validation happens entirely in your browser with the native parser, so the text you paste is not sent anywhere. This makes it a practical choice for checking internal payloads on your own device.
Common Problems and Fixes
Unexpected token error
This usually means a single quote, an unquoted key, or a trailing comma. JSON requires double quotes around every key and string and forbids a comma after the last element. Jump to the position named in the error message and correct that character.
The summary only shows part of my data
By design the summary previews the top level: it lists up to the first five object keys, truncates string previews at 40 characters, and does not expand nesting beyond two levels deep. The full document is still valid even though only a sample is shown.
Comments make my JSON invalid
Standard JSON does not allow comments, so lines with // or /* */ will fail. Remove the comments before validating, or store notes in a dedicated key such as a "_comment" string field.
Nothing happens after pasting
The result panel stays hidden when the field is empty or contains only whitespace. Make sure your text is actually in the box, then trigger validation by typing a character or pressing Validate JSON.