Validates as you type and highlights errors with the exact line and position of the syntax problem.
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Detailed Error Report
Shows the exact error message, line number and character position to pinpoint invalid JSON quickly.
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Structure Analysis
Reports key count, nesting depth, array count and byte size for valid JSON.
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100% Private
All validation runs in your browser using JSON.parse(). Your data is never sent anywhere.
⭐ User Reviews
4.9
⭐⭐⭐⭐⭐
Based on ratings from verified users · 99% recommend
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Dan M.
Yesterday
⭐⭐⭐⭐⭐
The error line/position reporting is excellent. I pasted a 500-line API response and it pinpointed the exact character where the syntax broke. Saved me 10 minutes of debugging.
JSON Validator
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Yuki T.
3 days ago
⭐⭐⭐⭐⭐
The structure analysis (key count, depth, arrays) is a great bonus on top of basic validation. I use it to quickly understand an unfamiliar JSON payload before writing parsing code.
JSON Validator
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Priya K.
1 week ago
⭐⭐⭐⭐⭐
Validate & Format in one click is my daily workflow for checking API responses. The status bar colour change from blue to green/red is a great visual cue. Fast and reliable.
JSON Validator
B
Ben S.
2 weeks ago
⭐⭐⭐⭐⭐
Best free JSON validator I have tried. No ads, instant result, clear error messages. The byte size stat is helpful for checking payload limits before submitting to our API.
JSON Validator
📖 How to Use
1
Paste JSON
Paste your JSON in the input field — validation starts automatically as you type.
2
Check the Status Bar
Green = valid JSON. Red = invalid with error message and position.
3
Read the Report
The right panel shows key count, depth, array count and byte size for valid JSON.
4
Fix Errors
The error detail box shows the exact line/column and surrounding context for invalid JSON.
JSON validation checks whether a string conforms to the JSON specification (RFC 8259). It verifies correct syntax: properly quoted keys, no trailing commas, correct use of brackets/braces, valid escape sequences and no JavaScript-specific syntax like undefined or functions.
What are common JSON syntax errors?+
The most common errors are: trailing commas after the last item in an array or object, single-quoted strings (JSON requires double quotes), unquoted keys, missing commas between items, invalid escape sequences, and comments (not allowed in JSON).
What is the difference between JSON and JavaScript object literals?+
JSON is a strict subset of JavaScript object syntax. JSON requires all keys to be double-quoted strings, does not allow trailing commas, does not support undefined, Date objects, functions or NaN/Infinity. JSON.parse() enforces all of these rules.
Can I validate JSON with comments?+
Standard JSON (ECMA-404) does not allow comments. Files with .jsonc extension or embedded in VS Code settings may have comments, but these require a JSONC parser — strip comments before using a standard validator.
What is the maximum JSON size I can validate?+
There is no hard limit — the constraint is your browser tab memory. In practice, files up to several MB validate instantly. For very large files (50MB+) consider a server-side tool.
💡 Why Use This Tool?
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100% Private
All processing runs in your browser — your code and data never leave your machine.
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Instant
Results appear as you type or with a single click — no waiting.
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Copy & Download
Copy the output to clipboard or download as a file with one click.
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Free & No Login
Completely free, no account required, unlimited use.