Hex color
Matches short and full hex color strings.
^#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6})$ Text & Regex 5 min read 2026-03-11
Common Regex Patterns You Will Reuse Constantly
A quick reference for common regex patterns, what they do, and what to watch out for before copying them into production.
Intro
Most regex work is not inventing patterns from scratch. It is adapting common patterns to your exact data, engine, and validation rules.
A good cheatsheet is useful only if it also explains where copied patterns tend to fail.
What is it?
Common regex patterns are reusable starting points for validation or extraction tasks such as IDs, dates, hex colors, and basic slugs.
They are templates, not universal truth. Real inputs often require tighter constraints.
Why it matters
- A vetted pattern saves time when building forms or cleaning data.
- Knowing the limits of a pattern prevents false confidence.
- Testing before shipping avoids silent parsing bugs.
Examples
Simple slug
Useful when validating lowercase kebab-case identifiers.
^[a-z0-9]+(?:-[a-z0-9]+)*$Common mistakes
- Copying a pattern without checking engine compatibility.
- Using a “simple email regex” as if it covered every real-world address.
- Skipping anchors and accidentally matching substrings.
- Ignoring whether case sensitivity should be explicit.
Use the tool
Ready to try Regex Tester?
Test regular expressions against input text.
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Can I trust regex patterns copied from the internet?
Only after testing them against your real input. Many examples are oversimplified or tuned for a different regex engine.
What makes a regex cheatsheet useful?
Concise patterns, clear examples, and notes about edge cases and failure modes.