Express Lint

About Express Lint

Express Lint is a comprehensive suite of developer tools designed for modern web development workflows. Our mission is to provide the fastest, most reliable JSON validation, text comparison, and formatting experience while maintaining complete privacy and security for your sensitive data.

What's here

JSON ValidatorValidate JSON, find the exact line and column of a syntax error, and repair it.JSON DiffCompare JSON as data: key order is ignored and type changes are called out.Text DiffCompare two blocks of text with character-level highlighting, split or unified.JSON BeautifierPretty-print minified JSON with 2-space, 4-space or tab indentation.JSON MinifierStrip whitespace from JSON and see exactly how many bytes you saved.JSON ViewerExplore JSON as a collapsible tree, with search and copyable paths.JSON ↔ YAML ConverterConvert JSON to YAML and back, with key order, types and merge keys handled.JSON ↔ CSV ConverterConvert JSON to CSV and back, with nested keys, types and Excel handled.Base64 Encode & DecodeEncode and decode base64 with correct UTF-8. Emoji, accented text and CJK survive.JWT DecoderDecode a JWT header and payload. The token never leaves your browser.JSON error referenceEvery common JSON parse error, what it means, and the fix.

100% Private

All processing happens locally in your browser. We never send your content to any server, ensuring complete privacy for sensitive code and configurations.

Lightning Fast

No network requests means instant validation, formatting and diff comparison. Works perfectly offline and handles large files efficiently.

Developer Focused

Built by developers, for developers. Features keyboard shortcuts, GitHub-style diffs, intelligent error recovery, and professional interfaces.

Advanced Comparison

Character-level diff highlighting, split and unified views, difference navigation, and support for multiple file formats.

Key Features

✓Advanced JSON syntax validation with intelligent error detection
✓Automatic JSON repair for common syntax errors
✓Character-level text diff highlighting with precision accuracy
✓GitHub-style split and unified diff views
✓Navigation between differences with keyboard shortcuts
✓Real-time syntax highlighting with line numbers
✓Drag and drop file support for JSON and text files
✓Complete client-side processing for maximum privacy
✓Dark mode interface optimized for developers
✓Your content is never uploaded or stored - it stays entirely in your browser
✓Professional interface designed for developer workflows
✓Intelligent whitespace and formatting detection
✓Export and copy functionality for processed content
✓Mobile-friendly responsive design
✓Offline functionality - works without internet
✓Advanced error recovery and formatting suggestions

Why Express Lint?

For DevOps Engineers: Validate configuration files, compare deployment scripts, and debug JSON APIs with confidence.

For Frontend Developers: Debug API responses, validate form data, and compare component configurations with precision.

For Backend Developers: Test JSON schemas, validate API payloads, and compare database configurations efficiently.

Technical Excellence

Performance

  • JSON up to 50 MB, text diff up to 20 MB combined
  • Large files are read in chunks and parsed off the main thread
  • The viewer renders only the branches you have opened
  • Zero server dependencies, so the tools work with no network at all

Those ceilings come from benchmarks in the repository rather than from guesswork, and each tool says so when you cross one.

What is collected

Your content is not. Page views are. For each page you visit we record the address, the referrer and a location worked out from your IP address, so we can see which tools people use. If you accept the notice we also store a device identifier, which is what tells a return visit from a new one. Everything is deleted after 90 days, and Do Not Track is honoured.

The privacy page lists every field, every key stored in your browser, and how to have your records deleted.

Who it is for

Anyone who has an API response that will not parse, two config files that should match but do not, or a token they need to read. You should not have to paste work data into someone else's server to answer questions like those.

Contact

Questions or feedback? Email scamplabs@gmail.com.

Your JSON and text are processed entirely in your browser and are never sent anywhere. To understand how the site is used we record each page view (the page, the referrer and an approximate location from your IP address) and keep it for 90 days. Nothing is stored on your device unless you choose it. Accept to also store a device identifier here and record your browser and device characteristics, which is what lets a return visit be told from a new one. Decline and nothing is sent at all. We respect Do Not Track. See our privacy policy.