Strict JSON, not JavaScript
JSON requires double-quoted strings and keys. Comments, undefined, functions, single quotes, and trailing commas are not part of standard JSON.
Private developer tool
JSON Validator Online
Check whether JSON is syntactically valid before you send, store, or deploy it. The validator is the primary action here and reports a useful error position when the browser provides one.
Your JSON stays in your browser.
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Paste JSON or upload a .json file to begin.
Shortcut: Ctrl/Cmd + Enter validates the input. Files and JSON content stay in this browser.
Syntax checking
What does the JSON validator check?
The validator parses input according to JSON syntax. It catches common problems such as missing braces or brackets, trailing commas, single-quoted strings, unquoted property names, invalid escape sequences, and separators in the wrong place.
When the JavaScript parser includes a character position, ToolsWeave maps it to a line and column and shows nearby source with a pointer. A valid result confirms syntax only; it does not prove that fields match an external API schema or that values are correct for your application.
How to validate JSON online
- 1
Add the JSON
Paste text into the input editor or open a local .json file.
- 2
Select Validate JSON
The browser parses the complete document without sending it to a server.
- 3
Inspect any error
Use the message, line, column, excerpt, and pointer when those details are available.
- 4
Format valid data
Beautify valid JSON for review, or minify it when you need a compact copy.
Useful error location
The checker derives line and column details from the parser's character position and displays a nearby excerpt where supported.
Validation versus schema checking
Syntax validation confirms that the text is JSON. It does not enforce required properties, data types, or business rules from JSON Schema.
Format after validation
Once syntax is valid, use the same working engine to create readable indented output, copy it, or download a formatted file.
Frequently asked questions
How do I check whether JSON is valid?
Paste or upload the JSON and select Validate JSON. A success message confirms valid syntax; invalid input receives an error and location details when supported.
Does the validator show the error line?
Yes, when the browser parser reports a source position. ToolsWeave converts that position to a line and column and shows nearby text.
Will the tool repair invalid JSON automatically?
No. Automatic repair can change meaning. The validator identifies the issue so you can make an intentional correction.
Does this validate against JSON Schema?
No. This page checks JSON syntax only; it does not evaluate a separate schema or API contract.
Can I format JSON after validating it?
Yes. The same tool includes Format JSON and Minify actions, so valid content does not need to be moved to another page.
Is sensitive JSON uploaded?
No. The current checker uses a worker in your browser, and analytics does not receive JSON content or filenames.
Related developer tools
Use the dedicated JSON Formatter, then move valid object-based data into a table with the JSON to CSV converter. You can also convert CSV back to JSON or browse the Developer Tools collection.