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Patterns · options · live match preview

Check a pattern live and load common ones with a single click.

Pattern
//g
0 matches
Flags
Common patterns
Match preview
연락처 010-1234-5678, 회사 02-555-0101
이메일 dev@example.com · 문의 support@util-platform.dev
참고 https://util-platform.dev/tools
ID user_12345 · alice99
IPv4 192.168.0.1 (내부망)
색상 #3a4bd0 · #fff · #ff6b35
Everything happens in your browser. Nothing is uploaded.

When to use it

To check whether strings like phone numbers and emails match a rule, or to pull specific fragments out of a long text. Matches update live as you edit the pattern.

How it works

Type the pattern in the top input, then toggle g · i · m · s · u · y as flags. The right pane highlights live. The pill row below offers common patterns (phone, email, IPv4, etc.) — click one and tweak from there.

Common pitfalls

  • Hangul doesn't match — \\w excludes Hangul. Use [가-힣], or the u flag with Unicode properties (\\p{L}).
  • Special characters — . ? + * ( ) [ ] { } | \\ must be escaped with \\ to match literally.
  • Greedy matching — .* grabs as much as it can. Use .*? for the minimal match.
  • Too slow — Patterns like (a+)+ can explode (ReDoS). Anything over 500ms is cancelled automatically with a notice.
  • Input over 100KB — Blocked to protect browser performance. Slice a sample first.

Where does your input go?

Both the pattern and the target text run in your browser. Nothing is uploaded or saved to local storage. Close the tab and it's gone.

Frequently asked questions

Why doesn't my regex match Korean characters?
`\w` only matches ASCII letters, digits, and underscore. To match Hangul, use `[가-힣]` for syllables, or the `u` flag with `\p{L}` for any letter. The "Hangul" preset loads this pattern in one click.
What does the 'g' flag do?
Global flag. Without it, the regex stops at the first match. With it, every match in the input is found. Usually on by default for testing.
Why is my pattern reported as too slow?
ReDoS risk — patterns like `(a+)+` or `(a|aa)+` have nested quantifiers that explode exponentially with input length. The tool aborts patterns that take more than 500ms to protect your browser. Tighten the pattern (often `a+` alone is enough).
Can I test multi-line strings?
Yes. The `m` (multiline) flag makes `^` and `$` match line starts/ends. The `s` (dotall) flag makes `.` match newlines.
How do I escape special characters?
`. ? + * ( ) [ ] { } | \` are regex metacharacters; precede them with `\` to match them literally (e.g., `\.` for a period). Most lose their special meaning inside `[ ]` character classes.