JSON Validator
Input JSON
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Validation Result 
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JSON Validator Online Free — Check JSON Syntax, Errors & Schema — Free Online Tool

Validate JSON syntax online free. Instant error detection with exact line and column numbers. View key count, depth, type breakdown. Upload .json files. No signup.

Free Forever
No Signup
No Upload
100% Private
Browser-based

Features

Built for real developer workflows. No fluff, just the tools you need.

✓

Instant Validation

Validates as you type using browser-native JSON.parse(). No button needed — errors appear the moment they occur.

📍

Exact Error Position

See the precise line and column of every syntax error. The context panel highlights the problem character with a red indicator.

📊

Deep Structure Analysis

Key count, nesting depth, file size and minified size — plus a complete breakdown of strings, numbers, arrays and objects.

📁

File Upload

Upload .json files directly. Useful for validating exported API responses, config files or database exports without copy-pasting.

💡

Fix Suggestions

Error messages include actionable hints. Trailing comma? We say so. Missing bracket? We highlight the line.

🔒

100% Private

Your JSON is validated using browser JavaScript. No data is ever transmitted to any server.

How to use

Get results in seconds — no account, no file upload required.

1

Paste or upload JSON

Type or paste JSON into the left panel, or upload a .json file.

2

Read the validation result

Valid JSON shows a full structure analysis. Invalid JSON shows the error location with context.

3

Fix and revalidate

Edit the JSON based on the error hint and watch validation update in real time.

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Frequently asked questions

What makes JSON invalid?
▾
The most common causes: trailing comma after the last item, single quotes instead of double quotes, unquoted keys, undefined or NaN values, and mismatched or missing brackets.
Does it validate JSON Schema?
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This tool validates JSON syntax (RFC 8259). JSON Schema validation — checking that data matches a defined structure — requires a schema definition file and is a separate operation.
What is the key count?
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The key count is the total number of keys across all objects at every nesting level, not just the top level. It gives a sense of how much data the JSON contains.
Can it handle large files?
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File uploads are limited to 5MB for performance. Pasted JSON can be larger — validation is only limited by your browser's memory.
What does depth mean?
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Depth is the maximum number of nesting levels. A flat object has depth 1. An object containing an object containing an array has depth 3.
Is it safe to validate sensitive JSON?
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Yes. Validation runs entirely in your browser with no server contact. Safe for API keys, tokens, database exports and confidential config files.