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Validate JSON

Check JSON syntax and review a formatted preview in your browser.

Browser-only processing: validation happens locally and your JSON is not uploaded.

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About JSON Validator

JSON Validator checks whether your JSON can be parsed correctly and helps you spot syntax issues faster. It is useful for APIs, config files, test payloads, and debugging. When the JSON is valid, you also get a formatted preview without sending data anywhere. Whether you are optimizing assets for a US-hosted site on AWS, Cloudflare, or Vercel, trimming email attachments for Gmail and Outlook, or submitting documents to federal portals, this tool keeps your files lean and your workflow fast — all without uploading anything to a server.

Optimized for Users in the United States

If you are working in the United States, file size matters for email providers like Gmail (25 MB attachment cap), Outlook, and popular US hosting platforms. Compressing images and documents before uploading to Amazon S3, Cloudflare, or Netlify keeps your bandwidth costs down and improves Core Web Vitals for American visitors on both fiber and mobile networks.

  • Most US email services reject attachments above 25 MB — compress to stay under that limit without switching to Google Drive or Dropbox.
  • For US-based e-commerce on Shopify, aim for product images under 200 KB to keep your Google PageSpeed score competitive.
  • Social platforms popular in the US — Instagram, Facebook, X (Twitter), and LinkedIn — each re-encode uploads, so feed them the smallest high-quality source file you can.
  • Many US government and healthcare portals restrict document uploads to 5–10 MB; pre-compressing PDFs avoids upload failures.
How to Validate JSON Online
  1. 1
    Paste your JSON

    Copy your JSON into the input editor.

  2. 2
    Run validation

    Check the JSON syntax in your browser and inspect any reported line or column details.

  3. 3
    Use the preview or fix the error

    If the JSON is valid, copy or download the formatted preview. If not, fix the reported syntax issue and validate again.

Frequently Asked Questions

What does JSON validation check?

It checks whether the JSON syntax is valid and can be parsed correctly by the browser.

Can this tool show line and column errors?

Yes. When the browser exposes the parsing location, the validator shows the related line and column details.

Does the validator also format valid JSON?

Yes. When the JSON is valid, the tool shows a formatted preview that you can copy or download.

Is validation done in the browser?

Yes. All validation is performed locally in your browser for privacy-first handling.

Will this work with my Gmail or Outlook attachments?

Yes. Gmail and Outlook both cap attachments near 25 MB. Our tools can shrink most files well under that limit so you can attach them directly instead of linking to Google Drive or OneDrive.

Can I use this for sensitive business or healthcare documents?

Since all processing happens locally in your browser and nothing is uploaded, your files never touch our servers. This client-side approach supports privacy-conscious US workflows — still follow your own organization's data policies.

Does it work on Mac, Windows, and mobile?

Yes. Our tools run in any modern browser on macOS, Windows, ChromeOS, Linux, iOS, and Android. No downloads or installations required.

Is there a file size limit?

Most tools handle files up to 50 MB each. For larger files, process them in smaller batches for the smoothest experience.

Why Choose Let Compress?
  • No upload required — your files stay on your device, aligning with US privacy expectations
  • Free forever, no sign-up or credit card — we never sell your data
  • Batch process dozens of files at once — built for fast US broadband and 5G workflows
  • Tuned for US-hosted sites on AWS, Cloudflare, Vercel, and Netlify
  • Runs in any modern browser — Chrome, Safari, Firefox, Edge on Mac, Windows, and mobile
  • No file quotas or daily limits — compress as much as your project needs

Learn More About Image Compression

Explore these authoritative resources to deepen your understanding of image compression and optimization.

MDN Web Docs: Image Optimization

Comprehensive guide on image optimization for web performance by Mozilla.

Google Web Fundamentals: Image Optimization

Best practices for image optimization from Google's web performance team.

W3C WebP Specification

Official W3C specification for the WebP image format.