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Regex Checker

Test and debug regular expressions in real-time with syntax highlighting, capture group extraction, and preset templates.

Regular Expression Pattern

/

/g

Flags:

Test Text

0 chars / 0 lines

Match Results & Highlight

No match
0 ms
Enter text to see match highlights here.

How to Use​

  1. Select a Preset or Enter a Pattern: Choose from common templates (Email, URL, Phone Number, Date, etc.) from the dropdown menu, or type any custom regular expression into the pattern input field.
  2. Configure Flags: Click the flag buttons beneath the pattern input (g: Global, i: Ignore Case, m: Multiline, s: dotAll, u: Unicode, y: Sticky) to toggle them on or off.
  3. Enter Test Text: Type or paste the target text into the "Test Text" input area.
  4. Inspect Match Results & Highlights: Matches are evaluated in real-time. Matching segments in your text are immediately highlighted with alternating colors.
  5. Examine Capture Groups: If your pattern includes capturing groups (...) or named capture groups (?<name>...), detailed extraction results and exact index ranges are displayed in individual cards.
  6. Copy and Share: Use the "Copy Pattern" or "Copy Matches" buttons to copy results to your clipboard. The tool automatically synchronizes with URL query parameters (?p=...&f=...&t=...) for instant sharing and bookmarking.

Key Features​

1. Built-in Preset Templates​

Quickly test common patterns with 10 pre-configured templates:

  • Email Address: Standard RFC-compatible email pattern
  • URL (HTTP/HTTPS): Web addresses with optional query strings and hashes
  • Postal Code (Japan): Japanese postal codes (100-0001 or 1000001)
  • Phone Number (Japan): Landlines, mobile phones, and toll-free numbers
  • Date: YYYY-MM-DD or YYYY/MM/DD with named capture groups
  • Time: HH:MM:SS or HH:MM
  • IPv4 Address: Valid IP address format (0.0.0.0 to 255.255.255.255)
  • Alphanumeric: Full alphanumeric text matcher
  • HTML Tags: Tag names, attributes, and inner contents extractor
  • Hex Color Code: #RGB, #RRGGBB, and #RRGGBBAA color codes

2. Full Flag Support​

Supports all standard JavaScript regex flags: g (Global), i (Ignore Case), m (Multiline), s (Dot All), u (Unicode), and y (Sticky).

3. Numbered & Named Capture Groups​

Extracts both standard numbered groups ($1, $2, ...) and ES2018 named capture groups ((?<name>...)), showing values and exact start/end character positions.

4. Real-time Syntax Highlighting & Performance Metrics​

Segments matched text dynamically with high-contrast highlight styling, tooltips showing match ranges, and sub-millisecond execution time tracking.

5. URL Synchronization & LocalStorage Backup​

All inputs (pattern, flags, and test text) are synchronized with URL search parameters and saved in LocalStorage, preventing accidental data loss upon reload.

Privacy First (100% Client-Side Processing)

🔒 All processing is done locally within your browser. Your regular expressions and test texts are never sent to any external server. You can safely test confidential logs or personal information.