A single-file, browser-based collection of developer tools. No build step, no backend, no sign-up — just open index.html and get to work.

Live Demo

Format raw IDs/values into any output format with processing options.

• 9 output formats: SQL IN (string/numeric), CSV, comma-separated, JSON array, Python list, Markdown list, one-per-line, custom template
• Remove duplicates, sort (A-Z, Z-A, numeric), case conversion
• Prefix/suffix per item, regex filter, find & replace
• Chunk/batch size for SQL 1000-item limits
• Column name input for full WHERE col IN (...) generation
• Smart input parser — auto-detects JSON arrays, SQL IN clauses, CSV, tab-separated, mixed quotes
• Live preview, drag & drop file import, export to file
• URL state — settings encoded in query string for bookmarking/sharing

Validate, format, and explore JSON data.

• Real-time validation with detailed error messages
• Syntax-highlighted formatted output
• Minified output (single line)
• Interactive collapsible tree view
• Click any key in tree to copy its JSON path
• Configurable indent (2 spaces, 4 spaces, tab)
• Sort keys alphabetically (recursive)
• Auto-fix common issues: trailing commas, single quotes, unquoted keys, JS comments
• Export as .json

Live markdown editor with full GFM support.

• Real-time preview as you type
• GitHub Flavored Markdown: tables, task lists, strikethrough
• Syntax-highlighted code blocks (all languages via highlight.js)
• Mermaid diagram rendering (flowcharts, sequence diagrams, etc.)
• Auto-generated table of contents
• Copy code buttons on every code block
• Write mode (type markdown) or Upload mode (drag & drop .md files)
• Export as self-contained HTML file
• Word/line/character count

Convert between Unix timestamps and human-readable dates.

• Live ticking clock showing current Unix timestamp
• Epoch to Human: auto-detects seconds/milliseconds/microseconds/nanoseconds
• Human to Epoch: native date picker + free-text parsing (Jan 15 2024, ISO 8601, etc.)
• Relative time display ("3 months, 12 days ago")
• Quick buttons: Now, +1 hour, +1 day, Y2K38, Today midnight, +1 week/month/year
• Every result row has a copy button
• Batch convert: paste many timestamps or dates, convert all at once

Encode and decode text in multiple formats.

• 3 modes: Base64, URL encoding, HTML entities
• Encode or Decode direction toggle
• Live processing as you type
• Swap input/output (auto-flips direction)
• Byte and character counts
• Full UTF-8 support

Test regular expressions with live feedback.

• Live match highlighting directly on the test string
• Flag toggles: g (global), i (case insensitive), m (multiline), s (dotall)
• Match list with index positions and capture groups (1ドル, 2ドル, ...)
• Replace mode with group references and live preview
• Pattern library: 16 common patterns (email, URL, UUID, IPv4, hex color, phone, HTML tag, etc.)
• Error display for invalid patterns
• Copy all matches or replaced result

Decode and inspect JSON Web Tokens.

• Auto-decode on paste — splits header, payload, signature
• Color-coded raw token (blue header / purple payload / green signature)
• Syntax-highlighted decoded header and payload
• Claims table with human-readable labels (Issuer, Subject, Audience, etc.)
• Timestamp claims (exp, iat, nbf) auto-converted to dates
• Expiry badge: green "Valid" or red "Expired"
• Copy individual parts or full payload
• Sample JWT generator for testing

Compare two text blocks with a proper diff algorithm.

• LCS-based (Longest Common Subsequence) line diff
• Color-coded output: green additions, red deletions, grey unchanged
• Dual line numbers (original + modified)
• Options: ignore whitespace, ignore case, trim lines
• Stats: lines added, removed, unchanged
• Swap A/B button

Set operations on two lists of values.

• Intersection (A ∩ B)
• Only in A
• Only in B
• Union (A ∪ B)
• Count badges on each result
• Copy any result set

• Single HTML file — no build tools, no npm install, no framework
• Dark / Light theme — auto-detects system preference, toggle with button or Ctrl+D
• Keyboard shortcuts — Ctrl+Enter format, Ctrl+Shift+C copy output, Ctrl+D dark mode
• Responsive — works on desktop and mobile
• Toast notifications — non-intrusive feedback
• Drag & drop — drop files onto input areas
• URL state — formatter settings saved in URL for sharing

The core toolkit is zero-dependency. The Markdown tab loads 3 libraries from CDN:

• marked — Markdown parser
• highlight.js — Syntax highlighting
• mermaid — Diagram rendering

Everything else is vanilla HTML, CSS, and JavaScript.

# Clone and open
git clone https://github.com/tachodril/dev-toolkit.git
open dev-toolkit/index.html
# Or just download index.html and double-click it

No server required. Works offline (except Markdown tab CDN libs on first load).

Contributions are welcome. Since this is a single-file project, keep these in mind:

• Everything stays in index.html — no splitting into multiple files
• No build tools or transpilation
• No external dependencies for core tools (CDN libs only for Markdown)
• Test in both light and dark mode
• Test on mobile viewport

MIT