Text & String Tools

Regex Syntax Reference

A searchable reference covering the regex syntax you actually use — anchors, quantifiers, groups, lookaround, and flags — click any entry to copy it.

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Basic Matching

Pattern	Description	Example
`.`	Any single character (except newline)	a.c → abc, aXc
`\d`	Any digit (0–9)	\d+ → 123
`\D`	Any non-digit	\D+ → abc
`\w`	Word character (a-z, A-Z, 0-9, _)	\w+ → hello_123
`\W`	Non-word character	\W → space, !, @
`\s`	Whitespace (space, tab, newline)	\s+ → " "
`\S`	Non-whitespace	\S+ → word
`\t`	Tab character	—
`\n`	Newline character	—

Using This Regex Reference

Regular expressions are a universal tool supported in JavaScript, Python, Java, PHP, Ruby, Go, Rust, and virtually every other programming language, though minor syntax differences exist between engines.

JavaScript vs. other engines

JavaScript regex uses the ECMA-262 standard. Python uses the re module (PCRE-like). The main differences: Python supports verbose mode (re.VERBOSE) and named groups with (?P<name>...). JavaScript ES2018 added named groups (?<name>...) and lookbehind assertions.

Testing regex safely

Always test your regex against edge cases including empty strings, very long inputs, and inputs with special characters. For server-side regex applied to user input, set a timeout or character limit to prevent ReDoS (Regular Expression Denial of Service) attacks.

Common regex patterns

Email: ^[\w\.-]+@[\w\.-]+\.\w{2,}$ — URL: https?:\/\/[\w\-]+(\.[\w\-]+)+([\w\-\.,@?^=%&:/~\+#]*[\w\-@?^=%&/~\+#])? — Date (YYYY-MM-DD): ^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01])$

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How it works

Three steps, no setup

Search or scan

Look up a symbol by name or browse the full categorized list.

Read the explanation

Each entry includes a plain-language description and example pattern.

Click to copy

Grab the exact syntax and paste it straight into your pattern.

Common questions

Frequently asked questions

Does this cover lookahead and lookbehind?

Yes, both positive and negative lookahead/lookbehind assertions are included with examples.

Is this specific to one programming language?

It focuses on the widely-shared core syntax that works consistently across JavaScript, Python, and most other regex engines.

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Regex Syntax Reference

Basic Matching

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JavaScript vs. other engines

Testing regex safely

Common regex patterns

Three steps, no setup

Search or scan

Read the explanation

Click to copy

Frequently asked questions

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Basic Matching

Using This Regex Reference

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Common regex patterns