Check case sensitivity flags, Unicode property escapes, and greedy vs lazy quantifiers.

Nested quantifiers on user-controlled strings can explode; test adversarial inputs.

Toggle dotall and multiline flags depending on engine support.

Regex Tester

Test and validate regular expressions in real-time

Regular Expression Pattern

Flags

Global (g) Case Insensitive (i) Multiline (m) Dot All (s) Unicode (u) Sticky (y)

Test Text

Match Results

0 matches

Enter a regex pattern and test text to see matches

Quick Reference

Character Classes

\d digit

\w word char

\s whitespace

. any char

[abc] a, b, or c

[^abc] not a, b, or c

Quantifiers

* 0 or more

+ 1 or more

? 0 or 1

{n} exactly n

{n,m} n to m

Anchors

^ start

$ end

\b word boundary

Groups

(abc) capturing

(?:abc) non-capturing

\1 backreference

Common Patterns

Tip: This tool uses JavaScript's native RegExp. All matches are highlighted in real-time. Use the flags to modify matching behavior. Click on common patterns to quickly test them.

Regex tester: safer patterns for logs, validation, and parsing

Regular expressions excel at structured text extraction but are easy to get wrong. A live tester shows matches, capture groups, and catastrophic backtracking before you ship code to production.

Document the dialect you target—JavaScript, PCRE, and POSIX differ in subtle features.

Practical tips

Anchor patterns (^ $) when validating whole strings.
Prefer possessive or atomic groups when performance matters.
Escape user input before injecting into dynamic regex.
Add examples to code comments for the next maintainer.

Common questions

Why no match?: Check case sensitivity flags, Unicode property escapes, and greedy vs lazy quantifiers.
ReDoS risk?: Nested quantifiers on user-controlled strings can explode; test adversarial inputs.
Multiline logs?: Toggle dotall and multiline flags depending on engine support.

Related tools on Toolfex

Toolfex provides free online utilities for individuals and teams. Use these guides alongside each tool’s on-page controls. For privacy and data handling, see our Privacy Policy.