JSON Linter - Free Online Tool

Validate JSON Syntax, Detect Errors, and Check Code Quality

Professional JSON linter to validate syntax, detect errors, warnings, and code quality issues. Our free online JSON linter provides comprehensive error detection, best practice suggestions, and detailed reports to help you write better JSON. Perfect for developers who need to ensure JSON quality, catch common mistakes, and follow best practices.

Key Features:

What the Linter Checks:

No registration required. Start linting your JSON immediately. Our tool provides instant feedback with color-coded severity levels - red for errors, orange for warnings, and blue for informational suggestions. Perfect for ensuring JSON quality before deployment or API integration.

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How to Use JSON Linter - Step by Step Guide

Step 1

Input Your JSON Data

Start by providing your JSON data for linting. Whether you're working with JSON, checking API responses, or ensuring proper syntax, you have three convenient options:

Paste JSON: Copy and paste your JSON data directly into the editor
Upload file: Click upload to select a .json or .txt file from your computer
Use sample: Click "Sample" to load example data and explore linting features
Step 2

Review Instant Lint Results

The linter automatically analyzes your JSON and provides instant feedback with three severity levels. This goes beyond basic JSON validation to check code quality:

Errors (Red): Critical syntax issues that make JSON invalid
Warnings (Orange): Code quality issues like duplicate keys or empty values
Info (Blue): Best practice suggestions and performance tips
Step 3

Understand Issue Details

Each issue includes detailed information to help you fix problems quickly. The linter provides structured error messages similar to professional development tools:

Clear message: Plain English explanation of the issue
Location info: Path or line number where issue occurs
Issue code: Unique identifier for each type of problem

Step 4: Fix Issues and Re-lint

Fix the reported issues in your JSON editor. The linter will automatically re-check as you type. For RFC-compliant JSON, you can also use our JSON Fixer to auto-fix common syntax errors, or format your JSON for better readability.

Auto re-check: Linter updates results as you edit
Issue count: See total issues decrease as you fix them
Perfect status: Get green checkmark when all issues are resolved

Step 5: Export Lint Report

Save or share your lint results for documentation or team review:

Download report: Get a detailed text report with all issues and recommendations
Copy to clipboard: Quickly copy the report for documentation or issue tracking
Share with team: Use reports in code reviews or quality audits

Frequently Asked Questions

What does a JSON linter do?

A JSON linter validates syntax, detects errors, and checks code quality. It goes beyond basic validation to find issues like duplicate keys, empty values, deep nesting, and provides best practice suggestions. It's like a spell checker and style guide combined for your JSON.

What's the difference between errors, warnings, and info?

Errors (red) are critical syntax issues that make JSON invalid and must be fixed.Warnings (orange) are code quality issues that won't break JSON but may cause problems.Info (blue) are suggestions for best practices and performance improvements.

Why does the linter flag duplicate keys?

Duplicate keys in JSON objects are problematic because only the last value is kept - earlier values are silently ignored. This usually indicates a mistake or data modeling issue. The linter helps you catch these before they cause bugs in production.

Can the linter auto-fix issues?

The linter identifies and reports issues but doesn't auto-fix them, as fixing requires understanding your intent. For automatic syntax error repair, use our JSON Fixer tool. The linter is best for code review and quality assurance.

Is the linter free to use?

Yes, completely free with no limitations on file size, usage frequency, or features. No registration required. Lint unlimited JSON files with full error detection, warnings, and best practice suggestions at no cost.