About DevTools

Our Mission

DevTools was created with a simple goal: to provide developers with fast, reliable, and privacy-respecting tools for everyday tasks. Whether you are debugging an API response, generating unique identifiers for a database migration, or validating a configuration file, these tools are designed to get the job done without friction.

We believe that developer tools should be free, fast, and transparent. Every tool on this site runs entirely in your browser — no data is ever transmitted to a server, no account is required, and everything works offline after the initial page load.

Available Tools

JSON Formatter & Validator

A full-featured JSON formatting, validation, and exploration tool. Key features include:

• Real-time validation — Errors detected as you type, with precise line and column indicators
• Interactive tree view — Explore deeply nested JSON structures with expandable nodes
• Data statistics — Size, depth, key count, and type breakdown at a glance
• Multiple input methods — Paste, drag-and-drop, file upload, or load from URL
• Full RFC 8259 / ECMA-404 compliance via browser-native JSON.parse()

UUID Generator

Generate universally unique identifiers in three versions, with bulk generation and educational guides:

• Three versions — UUID v1 (time-based), v4 (random), and v7 (time-ordered)
• Format flexibility — Uppercase/lowercase, with or without hyphens
• Bulk generation — Up to 10,000 UUIDs at once with copy and download
• Cryptographically secure — Uses crypto.getRandomValues(), not Math.random()
• Full RFC 9562 compliance with correct version and variant bits

JWT Decoder & Encoder

A complete JSON Web Token tool for decoding, inspecting, verifying, and generating JWTs:

• Instant decoding — Paste any JWT to see the header, payload, and signature decoded in real time
• Claims inspector — Structured table view of all claims with human-readable descriptions and timestamp conversion
• Expiry detection — Visual badge showing whether a token is valid, expiring soon, or expired
• Signature verification — Verify HMAC signatures (HS256/HS384/HS512) using the Web Crypto API
• Token generation — Build JWTs from scratch with a visual editor and quick-add claim buttons

Cron Expression Generator & Parser

A complete cron expression tool for parsing, building, and validating cron schedules:

• Instant parsing — Enter any 5-field cron expression and see a plain-English description in real time
• Next execution preview — See the next 10 upcoming execution times calculated from the current date and time
• Visual schedule builder — Build cron expressions visually with clickable buttons for each field: Every, Specific, Range, or Step
• Common presets — Start from 16 common cron schedules and customize from there
• Field breakdown — Each of the 5 fields displayed individually with its meaning explained

Regex Tester

A real-time regular expression testing tool with match highlighting and group inspection:

• Real-time matching — See matches highlighted instantly as you type the pattern or test string
• Capture groups — Inspect named and numbered capture groups for each match
• Replace preview — Test replacement patterns and see the result in real time
• All JS flags — Full support for g, i, m, s, u, v, d, and y flags
• Error detection with descriptive messages for invalid patterns

Encoder / Decoder

Encode and decode text in multiple formats with real-time bidirectional conversion:

• Three encodings — Base64, URL (percent-encoding), and HTML entity encoding in one tool
• Real-time conversion — Type in either panel and see the result instantly in the other
• Unicode support — Full UTF-8 support including emoji and multi-byte characters
• Character counter — Input and output lengths displayed for quick size comparison
• Resizable side-by-side panels with per-panel copy and paste

Diff Viewer

Compare two texts and visualize differences with line-level and character-level highlighting:

• Two view modes — Unified diff (single column with +/- markers) and side-by-side diff (left/right panels)
• Character-level highlighting — Modified lines show exactly which characters changed, not just the whole line
• LCS algorithm — Uses the Longest Common Subsequence algorithm, the same family used by Git and professional diff tools
• Change statistics — Lines added, deleted, and unchanged at a glance
• Copy diff output — Export as unified diff text for sharing in issues and documentation

What Makes These Tools Different

• Complete privacy — All processing happens client-side. No backend, no database, no tracking of your input. Your data never leaves your device.
• No dependencies — Built with vanilla HTML, CSS, and JavaScript. No frameworks, no build steps, no npm packages. The entire site loads in milliseconds.
• Offline capable — After the initial page load, every tool works without an internet connection.
• Standards compliant — JSON formatting follows RFC 8259, UUID generation follows RFC 9562. We implement specifications precisely, not approximately.

Technical Details

DevTools is a static website consisting of HTML, CSS, and JavaScript files. It is hosted on Cloudflare Pages, a global CDN that ensures fast load times from anywhere in the world. There is no server-side processing — every feature runs in your browser.

The source code is intentionally simple and auditable — you can view it in your browser's developer tools at any time.

Contact

DevTools is a free tool built and maintained by an independent developer. If you have feedback, feature requests, or bug reports, feel free to reach out via email:

[email protected]