User Guide: Regular Expression Tester (Regex Matcher)
A **regular expression** (commonly known as *regex* or *regexp*) is a specialized sequence of character tokens forming search patterns. Developers, data analysts, and sysadmins widely employ regex for input forms validation (e.g. scanning emails, postal codes, or URLs), structural parsing, advanced search-and-replace routines, and parsing raw log files.
Our free interactive Regex testing utility allows you to compose patterns using the JavaScript native engine, toggle common execution modifiers (flags), and instantly validate them against custom test strings. The editor automatically highlights matched substrings and parses captures into an organized groups tree, facilitating painless troubleshooting.
How to test regular expressions online?
- Input your pattern in the **Regular Expression (Pattern)** field. Do not include leading or trailing slashes `/`, as the editor formats them dynamically.
- Toggle your required active **Flags**:
- **g (global):** Find all occurrences instead of halting at the first successful match.
- **i (case-insensitive):** Ignore case differences (makes `a-z` match `A-Z`).
- **m (multiline):** Restructure anchor assertions `^` and `$` to match the start/end of individual lines instead of the total block.
- Fill the **Test Text** box with your test inputs.
- Instantly inspect the colorful matches in the preview card. Successive matches toggle between blue and green highlights for easy debugging.
- Analyze the **Capture Groups** list below to see precise sub-expressions separated by parenthesis `(...)` blocks along with their start indexes.
Data Privacy & Security Guaranteed
Local Execution: We care deeply about your privacy. All pattern testing and string evaluations run entirely in your local browser sandbox via JavaScript's `RegExp` API. Your confidential strings never leave your device.