Query, format, compare, and explore JSON — right in your browser.
json.express — Query & explore JSON in your browser
What is this

json.express is a single-file, zero-dependency web app for working with JSON. Paste any JSON, write a query, and instantly see the result — syntax-highlighted, as a collapsible tree, or as auto-generated TypeScript interfaces.

No data ever leaves your browser. Everything runs client-side — parsing, querying, formatting, validating, comparing, and type inference. Your JSON stays yours.

The entire app state is compressed into the URL hash, so you can bookmark or share any state — input, query, highlights, and comments — with a single link.

Tools
Editor
Full editor with query, tree view, TypeScript generation, highlights, comments, and URL sharing
Format & Beautify
Pretty-print minified JSON with proper indentation
Validate
Check JSON syntax with strict and lenient modes, with error line numbers
Minify
Compress JSON by removing whitespace, with compression stats
Viewer
Syntax-highlighted JSON viewer with color-coded types
Tree View
Collapsible, interactive tree for navigating deeply nested structures
Query
Extract data with dot notation, wildcards, array slicing, and recursive descent
TypeScript Types
Generate TypeScript interfaces from any JSON structure
Compare & Diff
Side-by-side diff of two JSON objects showing added, removed, and changed fields
Query syntax

The query bar supports a rich path expression language:

users[0].name — dot notation and array indexing
users[*].email — wildcard to collect from all items
users[0:3] — array slicing
..id — recursive descent to find all id fields
["special-key"] — bracket notation for special characters

Ideas & use cases
🔎
Debug API responses
Paste a raw API response and drill down to the exact nested field you need. Great for exploring unfamiliar endpoints.
✍️
Generate TypeScript types
Switch to the TS view and get instant interfaces from any JSON. Copy them straight into your codebase.
🔗
Share JSON snippets
The URL encodes your data, query, highlights, and comments. Share a link with a teammate instead of pasting blocks of JSON in Slack.
🗒
Format & validate
Paste minified or broken JSON and instantly format, validate, or minify it. The lenient parser handles trailing commas and comments.
🔄
Compare JSON
Diff two JSON objects side by side. See exactly what fields were added, removed, or changed — useful for API versioning and config reviews.
🌳
Explore nested structures
Use the Tree view to expand and collapse deeply nested objects. Navigate large configs or data dumps without getting lost.
🖌
Highlight & comment
Click line numbers to highlight lines in the result. Add comments to highlighted sections — everything is stored in the URL for sharing.
📶
Works offline
json.express is a PWA. Once loaded, it works without an internet connection — perfect for flights or flaky Wi-Fi.
More features

Upload — load .json, .jsonl, .jsonc, and .txt files directly
Lenient parser — handles trailing commas, // comments, and /* */ block comments
Copy & download — one-click copy, or export as .json or .d.ts
QR code — generate a QR code for the current URL to scan from another device
Themes — light, dark, or follow your system preference
Zero dependencies — single HTML file, no build step, no frameworks

Blog

Developer guides, tutorials, and tips for working with JSON. Browse all posts.

About the author
Udi Talias
Udi Talias
Web engineer who creates things that live inside your browser. In love with JavaScript and building small, focused tools that do one thing well.
GitHub
Feedback & suggestions

Found a bug? Have an idea for a new feature? Want to suggest an improvement? Open an issue on GitHub — all feedback is welcome.