Highlight RegExp Matches in Text
Enter a regular expression pattern and see matches highlighted instantly in your text.
What Is This Regex Highlighter Tool?
This free online regex highlighter helps you instantly visualize which parts of your text match a given regular expression (RegExp). Whether you're a developer testing patterns, a data analyst extracting information, or a student learning regex, this tool provides real-time feedback with color-coded highlights so you can see exactly what your pattern matches.
Simply enter your regex pattern, toggle the flags you need (g for global, i for case-insensitive, m for multiline,
s for dotall, and u for unicode), and type or paste your text. The tool highlights every match in a dedicated output panel,
counts total matches, and lists unique matched strings — all updating in real time as you type.
Why Use This Regex Highlighter?
- Instant Visual Feedback: See matches highlighted in bright yellow as you modify your pattern or text.
- No Installation Required: Works entirely in your browser — no downloads, no sign-ups, completely free.
- Flag Toggles: Easily switch between global, case-insensitive, multiline, dotall, and unicode modes with one click.
- Preset Patterns: Quick-start with common regex patterns for emails, URLs, phone numbers, hex colors, and more.
- Match Statistics: Instantly see how many matches were found and view unique matched values.
- Developer & Learner Friendly: Clean monospace fonts and a distraction-free interface make it ideal for coding and studying.
Understanding Regex Flags
Flags modify how the regular expression engine interprets your pattern. Here's what each flag does in this tool:
| Flag | Name | Description |
|---|---|---|
| g | Global | Finds all matches in the text rather than stopping after the first match. |
| i | Case Insensitive | Makes the pattern match both uppercase and lowercase letters interchangeably. |
| m | Multiline | Changes ^ and $ to match the start/end of each line, not just the whole string. |
| s | Dotall | Allows the dot . to match newline characters as well. |
| u | Unicode | Enables full Unicode matching, important for international text and emoji. |
Common Regex Patterns to Try
Here are some useful patterns you can test with the tool right now:
| Pattern | Matches |
|---|---|
[A-Z][a-z]+ |
Capitalized words (e.g., London, Hello) |
[\w.-]+@[\w.-]+\.\w+ |
Email addresses |
https?://[\w./-]+ |
URLs starting with http or https |
\d{3}[-.]?\d{3}[-.]?\d{4} |
US phone numbers (various formats) |
#[0-9A-Fa-f]{6} |
6-digit hexadecimal color codes |
\b\w{4,}\b |
Words with 4 or more letters |
\$\d+(?:\.\d{2})? |
Dollar amounts (e.g., $1,234.56 — note: simplified) |
Tips for Using This Regex Highlighter Tool
- Start with a preset — click any preset chip to load a working pattern, then modify it to suit your needs.
- Toggle flags wisely — if you're not seeing matches you expect, check if the
i(case insensitive) org(global) flag needs to be turned on. - Watch for invalid patterns — if your regex syntax is incorrect, the pattern input border turns red and an error message appears. Fix the syntax to restore highlighting.
- Use the highlighted output — the output panel shows your text with every match wrapped in a yellow highlight, making it easy to visually scan for matches.
- Copy and share — the tool works entirely in your browser. You can copy the highlighted text or simply take a screenshot to share your findings.
Frequently Asked Questions
Is this regex highlighter free to use?
Yes! This tool is 100% free and works directly in your browser with no registration, no ads, and no data collection. Your text never leaves your device.
What version of regular expressions does this support?
This tool uses JavaScript's native RegExp engine, which supports most modern regex features including lookaheads, capturing groups, character classes, and Unicode properties.
Can I use this tool on my mobile phone?
Absolutely. The interface is fully responsive and works on smartphones, tablets, and desktop computers alike.
Does it support replacement or substitution?
This tool focuses on highlighting matches. If you need find-and-replace functionality, many code editors and IDEs offer that feature. This highlighter is designed to help you visually verify your pattern first.
💡 Pro Tip: Bookmark this page to quickly test regex patterns whenever you need to validate or extract data from text.
