Free developer tools.
A small family of focused, free, in-browser tools that explain confusing developer syntaxes in plain English. No signup, no upload, no tracking of your content.
On this site
📖 Regex explainer
Paste any regex, get a plain-English breakdown. Try it →
📚 Patterns library
Curated, rigorously tested regex patterns for common use cases. Browse →
📋 Regex cheat sheet
Every regex token, class, group, and flag on one printable page. View →
Sister sites & recommended tools
Other small, focused, free in-browser tools we like and recommend. Same philosophy: do one thing well, explain it clearly, no signup.
⏰ crontabsheet.com
The sister site. Cron expression explainer, builder, English-to-cron translator, and platform tools for AWS, GitHub Actions, Kubernetes, Quartz, and more.
📐 Square footage calculator
Calculate area in square feet for rooms, lots, or any rectangular space — handy for flooring, paint, and real estate.
％ Percentage calculator
Everyday percentage math — increase, decrease, "what percent of X is Y", and more.
🎂 Age calculator
Calculate exact age in years, months, weeks, and days between any two dates.
🔤 Base64 encode / decode
Encode strings or files to Base64, or decode Base64 back to plain text — all in your browser.
🔗 URL encode / decode
Convert URLs and query parameters to and from percent-encoded form for safe transmission.
🔒 Password strength checker
Estimate how strong a password is and how long it would take to crack — entirely client-side.
📝 Word counter
Count words, characters, sentences, paragraphs, and reading time for any text.
🆔 UUID generator
Generate UUIDs (v1, v4, v7, and others) one at a time or in bulk, with explanations of each version.
🧰 JSON tools
Format, validate, minify, and convert JSON. The Swiss-army knife for JSON in the browser.
#️⃣ Hash generator
Generate MD5, SHA-1, SHA-256, SHA-512, and other hashes from any input text.
⏱️ Epoch time converter
Convert between Unix epoch timestamps and human-readable dates across any timezone.
🔁 Text repeat
Repeat any string a given number of times — useful for testing, mock data, and load tests.
📏 Unit cheatsheet
Engineering and scientific unit reference — converters, cheat sheets, and printable charts for length, mass, energy, and more.
⏰ Hours calculator
Free hours and timesheet calculator with overtime and pay. Handles breaks, overnight shifts, and decimal hours.
🕐 Clock with us
Online alarm clock, timer, stopwatch, world clock, and time zone converter — all browser-based, no signup.
What's coming
More patterns. More long-form guides. A flavor converter that ports a regex from PCRE to JavaScript (or any other flavor pair) and tells you what changed. A ReDoS / catastrophic backtracking detector.
If there's a specific developer-tool gap you'd like filled, tell us.