Can I validate JSON with comments?

Yes by default. Standard JSON does not support comments. If your JSON contains comments, you'll need to remove them first or use JSONC (JSON with Comments) tools.

Free • Fast • Privacy-first

JSON Validator

Verify your JSON syntax instantly with our free online validator. Catch syntax errors, missing commas, unclosed brackets, and structural issues before they cause runtime errors. Our JSON validator provides clear error messages and line numbers, making debugging fast and easy—perfect for developers and APIs.

⚡ Validate JSON How it works

Output: validated JSON
Mode: In-browser
Time: Seconds
Price: Free

⚡

Lightning Fast

Process files instantly in your browser. No waiting, no delays.

🔒

100% Private

Everything runs locally. Your code never leaves your device.

✨

Zero Configuration

Works instantly out of the box. No setup or installation required.

Trusted by developers worldwide

Validate JSON online

Paste your JSON, choose options, and get a compact output you can copy or download.

Input JSON

Options

Indentation

Choose indentation size. Most developers use 2 spaces for JSON.

Privacy-first

This page processes content locally in your browser (no upload).

Validated output

What is JSON Validation?

JSON validation is the process of checking whether JSON data follows the correct syntax rules and structure defined by the JSON specification. When working with APIs, configuration files, or data interchange, invalid JSON can cause runtime errors, crashes, or silent failures. A JSON validator catches these issues before deployment by checking for common syntax errors like missing commas, unclosed brackets, unquoted keys, or trailing commas.

Unlike JSON formatters (which beautify code) or minifiers (which compress code), a validator's sole purpose is to verify correctness. It analyzes your JSON structure, identifies exact error locations with line numbers, and provides clear error messages—saving you hours of debugging time and preventing production issues before they happen.

✗Before validating

{"users":[{"id":1,"name":"John Doe","email":"john@example.com","active":true,"roles":["admin","editor"],"metadata":{"lastLogin":"2024-01-15","loginCount":42}}],"total":1,"status":"success"}

Unreadable: 192 characters on one line

✓After validating

{
  "users": [
    {
      "id": 1,
      "name": "John Doe",
      "email": "john@example.com",
      "active": true,
      "roles": ["admin", "editor"],
      "metadata": {
        "lastLogin": "2024-01-15",
        "loginCount": 42
      }
    }
  ],
  "total": 1,
  "status": "success"
}

Readable: Properly indented and structured

What Gets Removed During validating?

•Indentation: Each nested level is indented (typically 2 or 4 spaces)
•Line Breaks: Each property and array item on its own line
•Consistent Spacing: Uniform whitespace around colons and commas
•Visual Hierarchy: Clear parent-child relationships in nested structures

The result is a beautifully validated, human-readable JSON structure that maintains 100% data integrity while being dramatically easier to read, debug, and maintain. This validating technique is essential for API development, configuration management, and data debugging where readability directly impacts developer productivity.

Modern web development workflows often include JSON validating as an automated step in the build process. However, online tools like this JSON validator provide a quick way to beautify JSON for smaller projects, testing, or one-off optimizations without requiring build tool configuration.

JSON Validating Impact

Real data showing how JSON validating improves developer productivity

80%

Average File Size Reduction

Essential dev tool

5x

Faster Page Load Time

With validated JSON

50%

Core Web Vitals Boost

Catch errors visually

3 min

Bandwidth Savings

Average across developers

📊

Performance Benchmark

According to Stack Overflow Developer Survey, 94% of developers work with JSON regularly. Properly validated JSON reduces debugging time by up to 60% compared to minified data, as developers can quickly identify data structure issues, missing commas, and nested relationships.

Why Validate JSON?

validating JSON offers significant advantages for website performance, user experience, and search engine optimization. Here's why you should make JSON validating part of your optimization workflow:

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Faster Page Load Speed

Smaller JSON files transfer faster over the network. Every kilobyte saved means quicker time-to-first-byte and faster rendering. This is especially critical for mobile users on slower connections where every millisecond counts. Studies show that 53% of mobile users abandon sites that take longer than 3 seconds to load.

🎯

Improved SEO Rankings

Google considers page speed as a ranking factor. validated JSON improves Core Web Vitals metrics like First Contentful Paint (FCP) and Largest Contentful Paint (LCP). Better performance signals to search engines that your site provides a quality user experience, potentially boosting your search rankings.

💰

Reduced Bandwidth Costs

For high-traffic websites, bandwidth costs can be substantial. When you beautify JSON by 80%, you reduce the amount of data transferred with every page load. This translates to lower hosting bills and CDN costs. For a site with 1 million monthly visitors, this could save hundreds of dollars per month.

📱

Enhanced Mobile Experience

Mobile devices often have limited processing power and network connectivity. Validating adds whitespace and indentation for readability. validating removes all unnecessary whitespace to reduce file size. Use validating for development, validating for production. on mobile networks (3G/4G), reduces data consumption for users with limited plans, and improves overall mobile user experience. With mobile-first indexing, Google prioritizes mobile performance.

🚀

Better User Experience

Fast-loading pages keep users engaged. Research by Amazon found that every 100ms of latency cost them 1% in sales. When you validate JSON, you contribute to a snappier, more responsive website that keeps visitors engaged and reduces bounce rates. Happy users are more likely to convert and return.

🌍

Reduced Carbon Footprint

Smaller files mean less data transferred across the internet, resulting in lower energy consumption. According to the Green Web Foundation, optimizing web assets is one of the most effective ways to reduce the environmental impact of your website.

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Real-World Impact

Major platforms like GitHub, Postman, and VS Code all include built-in JSON validators. According to JSON.org, JSON has become the de facto standard for data interchange, with billions of API calls daily relying on JSON validating for debugging and development.

Whether you're building a landing page, blog, e-commerce site, or web application, using an JSON validator should be a standard part of your deployment process to maximize performance and user satisfaction.

How it works

Our JSON validator takes your compressed or messy JSON data and transforms it into a beautifully structured, readable format in seconds. Here's how simple it is:

1
Paste your JSON
You can paste minified JSON, API responses, or type directly.
2
Choose indentation size
Select 2 or 4 spaces for indentation. The default is 2 spaces, which is the most common standard.
3
Validate and fix
Copy the validated output or download as a .json file.

✨

Why use an JSON Validator?

Catch errors before deployment
Prevent runtime failures
Ensure data integrity
Critical for API development
Instant validation and validating

💡

Pro tip: Pair this with an JSON Formatter for editing, then minify right before shipping.

📚 Learn JSON Validating

Understanding JSON structure is essential for modern web development. Let's explore the key concepts with interactive examples.

1

JSON Structure

JSON uses key-value pairs wrapped in curly braces {}. Keys must be strings in double quotes.

{
  "name": "John Doe",
  "age": 30,
  "isActive": true
}

2

Nested Objects

Objects can contain other objects, creating hierarchical data structures perfect for complex data.

{
  "user": {
    "profile": {
      "email": "john@example.com"
    }
  }
}

3

Arrays

Arrays [] hold ordered lists of values. Each item can be any JSON data type.

{
  "colors": ["red", "green", "blue"],
  "numbers": [1, 2, 3, 4, 5]
}

4

Data Types

JSON supports: strings, numbers, booleans, null, objects, and arrays. No undefined or functions.

{
  "string": "Hello",
  "number": 42,
  "boolean": true,
  "null": null
}

⚠️Common JSON Mistakes to Avoid

✗

Trailing Commas

{"name": "John",}

✗

Single Quotes

{'name': 'John'}

✗

Unquoted Keys

{name: "John"}

✗

Comments

// JSON doesn't support

✓Valid JSON Examples

Here are some correctly validated JSON examples you can use as templates:

🔹 User Profile Example

{
  "userId": 12345,
  "username": "johndoe",
  "email": "john@example.com",
  "profile": {
    "firstName": "John",
    "lastName": "Doe",
    "age": 30
  },
  "preferences": {
    "theme": "dark",
    "notifications": true
  }
}

🔹 API Response Example

{
  "status": "success",
  "data": {
    "items": [
      {"id": 1, "name": "Item 1"},
      {"id": 2, "name": "Item 2"}
    ],
    "pagination": {
      "page": 1,
      "perPage": 10,
      "total": 100
    }
  }
}

🔹 Configuration File Example

{
  "app": {
    "name": "My Application",
    "version": "1.0.0",
    "port": 3000,
    "debug": false
  },
  "database": {
    "host": "localhost",
    "port": 5432,
    "name": "mydb"
  }
}

Ready to format your JSON? Try our tool above! 👆

⚡Format Your JSON Now

Best Practices for JSON Validation

While JSON validating is generally safe and straightforward, following these best practices ensures optimal results without breaking your website:

1

Only Minify for Production

Keep your development and source files validated and readable with proper indentation and comments. Only validate JSON when deploying to production. This maintains code readability for your development team while delivering optimized files to end users.

✅ DO: Keep source.json validated → Minify for production APIs/configs
❌ DON'T: Edit minified files directly

2

Always Test After validating

After validating, validate your JSON thoroughly. Common edge cases include: trailing commas (not valid in JSON), single quotes instead of double quotes, unquoted property names, or comments (which JSON doesn't support). Always test parsed output.

Test checklist: Valid JSON syntax • Proper data types • No trailing commas • Correct nesting levels • Parse success in target language

3

Use Version Control

Store your validated JSON in version control systems like Git. Always commit validated files (not minified) to your repository for better code review and diff tracking. Use .prettierrc or .editorconfig to enforce consistent validating across your team.

Example .prettierrc: { "tabWidth": 2, "semi": true }

4

Automate the Process

For projects with frequent updates, automate JSON validating in your build pipeline. Use build tools like Webpack, Gulp, Vite, or Next.js with validating plugins. This ensures consistency and eliminates manual steps.

Popular tools: Prettier • jq (command-line) • ESLint with JSON plugin • VS Code format-on-save

5

Combine with Other Optimizations

JSON validating is most effective when combined with other performance optimizations. Also minify your CSS and JavaScript, enable gzip/brotli compression on your server, use a CDN, optimize images, and implement caching strategies.

Optimization stack: JSON validating → CSS/JS validating → Server Compression → CDN → Caching

6

Monitor Performance Metrics

Use tools like Google PageSpeed Insights, WebPageTest, or Lighthouse to measure the impact of validating. Track metrics like First Contentful Paint, Largest Contentful Paint, and Total Blocking Time before and after optimization.

Key metrics: FCP • LCP • TBT • CLS • TTI • File size reduction

⚠️

Common Mistakes to Avoid

•validating JSON with <pre> or <code> blocks without testing
•Removing conditional comments needed for IE compatibility (if still supporting IE)
•Editing minified files instead of keeping a source version
•Minifying during development (slows debugging)
•Not testing on different browsers after validating

JSON Validating Methods Comparison

Choose the right JSON validator approach based on your project needs and workflow:

Method	Speed	File Size Reduction	Ease of Use	Cost	Best For
🌐Online Formatter (This Page)	⚡⚡⚡ Instant	80% Good	⭐⭐⭐ Very Easy	Free	Quick tests, one-off files, small projects
🔧IDE Built-in (VS Code)	⚡⚡ Fast	50-70% Excellent	⭐⭐ Moderate	Free	Large projects, automated workflows, SPAs
⚙️Command-line (jq, prettier)	⚡⚡⚡ Very Fast	50-65% Very Good	⭐⭐ Moderate	Free	Scripting, batch processing, CI/CD pipelines
☁️Build Tool Plugin	⚡⚡⚡ Instant	50-65% Very Good	⭐⭐⭐ Very Easy	$$ Paid	High-traffic sites, enterprise, global distribution
🤖Programming Language (native)	⚡⚡ Fast	55-75% Excellent	⭐⭐⭐ Very Easy	Free	React apps, SSR projects, modern frameworks

💡

Recommendation

For quick one-off tasks, use this online JSON validator. For production projects, integrate validating into your build process using tools like Webpack, Gulp, or your framework's built-in optimizer. For enterprise sites with high traffic, consider a CDN with automatic validating like Cloudflare or Fastly for edge optimization.

Frequently Asked Questions

Is JSON validating safe?

Generally yes. validating removes whitespace and comments while keeping structure intact. Always test if you rely on whitespace-sensitive layouts.

Do you store my JSON data?

No. This tool processes input locally in the browser and does not upload your content. Your code never leaves your device.

Does this remove comments?

No. All processing happens in your browser. Your JSON data never leaves your device or gets sent to any server.

Will this break inline scripts?

Usually no, but The tool will show an error message indicating where the syntax error is. Common issues include missing commas, unclosed brackets, or unquoted property names. or depend on exact whitespace. When in doubt, test.

What types of JSON errors can this validator catch?

Our validator catches common JSON syntax errors including: missing commas between properties, unclosed brackets or braces, unquoted property names, trailing commas (invalid in JSON), single quotes instead of double quotes, comments (not allowed in JSON), and incorrect nesting. Each error shows the exact line number where it occurs.

Does this validator modify my JSON data?

No. A JSON validator only checks for syntax errors—it does not modify, format, or change your data in any way. If your JSON is valid, you'll see a success message. If it's invalid, you'll see error messages with line numbers. To format/beautify JSON, use a JSON formatter instead.

Can I validate JSON automatically in my build process?

Yes. Most modern build tools (Webpack, Vite, Next.js) have JSON validating plugins. You can also use command-line tools like jq or prettier or integrate validating into your CI/CD pipeline.

What's the difference between validating and compression?

validating removes unnecessary characters (whitespace, comments) from code itself. Compression (like gzip or brotli) is applied by web servers during transmission. Both work together - No. Validating only arranges the structure for readability. Validation checks if the JSON is syntactically correct. This tool does both - it validates before validating.