Regex Builder
Build a regular expression by clicking tokens and presets — no syntax memorization.
Type a pattern below, paste text to test it against, and watch matches highlight as you go. Not sure where to start? Pick a template or insert ready-made tokens further down.
Start from a template
Insert regex tokens (click to add)
What is Regex Builder?
Regex Builder helps you construct a regular expression without needing to already know the syntax by heart. Instead of typing symbols like \d, \b, or (?:...) from memory, you click labeled buttons — "Digit", "One or more", "Word boundary" — and each one is inserted into your pattern at the cursor. There's also a row of ready-made presets (email address, URL, IPv4 address, and more) you can drop in as a starting point and tweak. As you build the pattern, it's tested live against a sample string you provide, with every match highlighted, so you can see the effect of each piece as you add it rather than writing the whole thing blind and hoping it works.
How to Use Regex Builder
- Optionally start from a common pattern preset (email, URL, IPv4 address, etc.) to save time.
- Click token buttons (character classes, quantifiers, anchors, groups) to insert them into the pattern at your cursor position.
- Type directly into the pattern field any time — the buttons and manual typing both work on the same field.
- Toggle the i/m/s flags if you need case-insensitive matching, multiline anchors, or dot-matches-newline.
- Paste a test string below and watch matches highlight live as you refine the pattern.
- Copy the finished pattern once it matches what you expect.
Examples
Building a simple digit pattern from scratch
Input: Click "Digit", then "One or more" → pattern becomes \d+
Output: Matches any run of one or more digits, e.g. "42" inside "Order #42 shipped"
Starting from a preset
Input: Click the "Email address" preset
Output: Pattern becomes [\w.+-]+@[\w-]+\.[\w.-]+, ready to test or extend
Common Mistakes
- Forgetting to replace the literal ... placeholder inside inserted group/set tokens with actual content.
- Forgetting to replace n/m placeholders inside quantifier tokens like {n} or {n,m} with real numbers.
- Expecting matches without providing a test string — the highlight area only appears once both a pattern and a test string are present.
- Assuming a preset pattern covers every edge case for its category — the Email/URL/phone-number presets are deliberately simple starting points, not full RFC-compliant validators.
Why Use This Tool
- No need to memorize regex syntax — build a pattern by clicking labeled tokens.
- Ready-made presets for common patterns (email, URL, IPv4, hex color, phone number).
- Live match highlighting as you build, not just after you're done.
- Works entirely client-side — nothing you type is sent anywhere.