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Regex Cheatsheet & Tester

Interactive regex reference with search, categories, and a live pattern tester. Copy tokens instantly and test patterns in your browser.

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What is the Regex Cheatsheet & Tester?

The Regex Cheatsheet & Tester gives you instant access to over 50 essential regular expression tokens — from anchors and character classes to lookaheads and flags. No more switching between documentation tabs or reading dense PDFs.

Why this tool?

  • Live search & filter: start typing and the cheatsheet narrows down instantly. Filter by category (Anchors, Quantifiers, Groups, Flags, etc.) with a single click.
  • Copy any token with one tap – no manual highlighting, just hit the copy button.
  • Built‑in pattern tester: paste your own regex, add flags, and run it against a test string. See every match, its position, and named group values — all client‑side, nothing leaves your browser.
  • Clean, responsive design that works just as well on a phone as on a desktop.

Whether you’re debugging a complex pattern or learning regular expressions from scratch, this tool keeps the entire JavaScript/PCRE‑compatible syntax at your fingertips.

How it works

1. Browse or search the cheatsheet

The entire reference is organized into logical categories (Anchors, Character Classes, Quantifiers, Groups, Lookarounds, Escaped Characters, Flags, and Common Patterns).

  • Search field – Type any keyword (e.g. “boundary”, “email”, “lookbehind”) to instantly filter matching tokens, descriptions, and examples.
  • Category dropdown – Pick a specific category or leave it on “All” to see everything.

Each token card shows:

  • The regex symbol(s) in a monospaced code block.
  • A short, plain‑English explanation.
  • An optional example (e.g. \d+ → matches “123”).
  • A copy button that puts the token directly onto your clipboard.

2. Test your own patterns

Below the cheatsheet, a live regex tester lets you experiment:

  1. Enter a pattern (e.g. \d{3}-\d{2}-\d{4}).
  2. Set optional flags – g for global, i for case‑insensitive, m for multiline, s for dotall, u for Unicode, y for sticky. Multiple flags are allowed (e.g. gi).
  3. Type or paste a test string.
  4. Click Run Test.

The result area shows:

  • The total number of matches.
  • Each match surrounded by quotes, preceded by its starting index.
  • Any named groups (e.g. (?<year>\d{4})) are displayed as groupName: "value".

Invalid patterns or unsupported flags trigger a clear, human‑readable error message.

3. Privacy & performance

Everything runs inside your browser. No data is sent to any server. The tool uses native JavaScript RegExp objects, so it’s fast and respects the same engine your production code will use.

Examples

Find an email regex pattern

Type “email” in the search field to instantly locate the common email validation token along with its description and example.

Search: email
Token: ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$, Description: Email (basic), Example: test@example.com

Test a date validation pattern

Paste a regex and a test string to see all matches, their indices, and named groups (if any).

Pattern: ^\d{4}-\d{2}-\d{2}$, Flags: g, Test string: 2023-01-01
1 match found:
[0] “2023-01-01”

Frequently asked questions

What exactly is a regex cheatsheet?

A regex (regular expression) cheatsheet is a quick‑reference table of the special characters, sequences, and constructs used to build pattern‑matching expressions. This interactive version adds search, copy, and a built‑in tester so you can experiment without leaving the page.

Which regex flavour does this cheatsheet cover?

All tokens and the live tester follow JavaScript (ECMAScript 2018+) syntax. That includes lookbehinds, named capture groups, Unicode property escapes (when using the u flag), and the standard PCRE‑like quantifiers and anchors.

How do I use the built‑in tester?

Scroll to the “Test a Pattern” section. Enter a regex pattern, any flags (e.g. gi), and a test string. Click Run Test. The tool shows every match, its position (index), and any named groups. Invalid patterns or flags are reported immediately.

Can I copy a token to my clipboard?

Yes – every token card has a copy button. Click it once to copy the exact regex symbol(s) (e.g. \b, [a-z], (?<=…)) to your clipboard. No extra selection or manual highlighting is needed.

What common real‑world patterns are included?

The “Common Patterns” category provides ready‑to‑use expressions for email addresses, URLs, dates (YYYY‑MM‑DD), UUIDs, and international phone numbers. You can copy and adjust them directly in your code.

Is my test data sent to a server?

No. Everything runs entirely inside your browser using JavaScript’s RegExp engine. No patterns, test strings, or results ever leave your device.

Why do I get a “No matches” result even though my pattern looks correct?

Check if the g (global) flag is needed to find multiple matches. Also verify that the pattern accounts for the entire string or partial match logic. Use the tester’s index output to debug where a match might be starting.

Can I use lookbehinds and named groups?

Absolutely. The tool supports ES2018+ features including positive/negative lookbehinds ((?<=…) and (?<!…)) and named capturing groups ((?<name>…)). The tester displays named group values when they are defined.

How do I search for a specific token or category?

Use the search bar at the top of the page – it filters tokens by keyword, description, or example. The category dropdown lets you jump to “Anchors”, “Quantifiers”, “Flags”, etc. instantly.

Is this cheatsheet suitable for beginners?

Yes. Every token includes a clear, plain‑language description and a concrete example. Paired with the interactive tester, it’s a great hands‑on learning tool. Start with simple patterns and build up gradually.

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