JSON Validator
Validate JSON syntax instantly with parsed structure preview, clear error reporting, and browser-based processing. Perfect for API payloads, config files, fixtures, and debugging malformed JSON.
What is JSON Validator?
The JSON Validator checks whether a string is valid JSON. It parses the input using the browser's built-in JSON parser and reports the exact line and column of any syntax error, along with a description of the problem. It also detects common mistakes like trailing commas, single quotes, and unquoted keys. All processing happens in the browser.
How does JSON Validator work?
This tool passes your text to JSON.parse and catches any thrown errors. When an error occurs, it extracts the position from the error message and highlights the approximate location in the input. For valid JSON, it confirms the parse succeeded and shows the top-level type (object, array, string, etc.).
Key Features
- Validates JSON syntax with exact error positions
- Detects trailing commas, single quotes, and unquoted keys
- Shows line and column of errors
- Confirms valid JSON with type information
- Handles nested structures to any depth
- Real-time validation as you type
- Copy validation report
- Reports parse errors with line and column positions for fast fixes
Common Use Cases
Debugging API request payloads
Validate a JSON body before sending it to an API to catch syntax errors early.
Checking configuration files
Verify that a JSON config file is syntactically valid before deploying it.
Finding errors in large JSON files
Locate the exact position of a syntax error in a large JSON document that is hard to scan visually.
Verifying generated JSON
Validate JSON output from a script or tool to confirm it produced well-formed data.
How to Use This Tool
Paste JSON
Enter JSON text in the input area.
Validate
Click Validate or wait for real-time validation. The tool checks the syntax.
Review the result
If valid, the tool confirms it and shows the data type. If invalid, it shows the error location and description.
Pro Tips
- 1
Trailing commas after the last item in an array or object are the most common JSON error.
- 2
JSON requires double quotes for keys and string values. Single quotes are not valid.
- 3
The tool shows the exact line and column to help you find errors quickly.
- 4
For very large JSON, paste the section around the error for faster validation.
Frequently Asked Questions
What common errors does it detect?
JSON validator detects syntax errors including trailing commas, single quotes instead of double quotes, unquoted keys, missing brackets, invalid escape sequences, and unexpected tokens.
Does it show where the error is?
Yes. The error message includes the line number and column position where the parser encountered the problem.
Is my JSON uploaded to a server?
No. All validation happens in your browser using JavaScript. The data never leaves your device.
Can I validate large JSON files?
Yes. The tool handles JSON of any size that fits in browser memory. The browser's JSON.parse is highly optimized.
Does it fix errors automatically?
No. The tool only reports errors. Use a JSON formatter or editor to fix the issues it identifies.