Which regex flavor does this tool use?

The tool uses JavaScript's built-in regular expression engine (ECMAScript regex). This is the same engine used in Node.js, all browsers, and many JavaScript frameworks. It supports most standard regex features including lookahead, lookbehind, named capture groups, and Unicode property escapes.

What is the difference between the g and m flags?

The g (global) flag finds all matches in the string rather than stopping at the first. The m (multiline) flag changes ^ and $ anchors to match the start and end of each line rather than the entire string. Both can be used together.

How do I use named capture groups?

Named capture groups use the syntax (? pattern). For example, (? \d{4})-(? \d{2}) captures year and month by name. The tool displays named group values in the match output.

Why are my matches not working with special characters?

Special regex characters like ., *, +, ?, (, ), [, ], {, }, ^, $, |, and \ must be escaped with a backslash to be matched literally. For example, to match a period use \. instead of .

Is my test data kept private?

Yes. All regex testing runs in your browser using JavaScript. Your patterns and test strings are never transmitted to any server.

All Tools›Debug & API›

Regex Tester

Free · No Server

Write a regex pattern, set flags, and test it against any string — matches highlight in real time.

Tests live · share a link to send your pattern

Pattern

Test String

Drag & drop a file, upload, or paste directly

2 matches found

Highlighted Matches

Match Details

"hello@aitechworlds.com"at index 14

"support@example.org."at index 40

What is Regex Tester?

The Regex Tester on AiTechWorlds is a real-time regular expression sandbox where you can write, test, and debug regex patterns against any test string. Regular expressions are powerful but notoriously difficult to get right — even experienced developers test patterns interactively. This tool shows every match highlighted inline in the test string as you type your pattern, lists all capture groups with their matched values, and explains common regex syntax errors. It supports all JavaScript regex flags (g, i, m, s, u) and displays global match counts, named capture groups, and match indexes. All testing runs in your browser with no server call — your regex patterns and test data stay completely private. AiTechWorlds provides this tool for developers, data engineers, and anyone who needs to write correct regular expressions without the trial-and-error of running code.

How to Use

1
Enter your regex pattern
Type your regular expression in the pattern field. Syntax errors are highlighted immediately.
2
Set flags
Toggle flags: g (global), i (case-insensitive), m (multiline), s (dotAll), u (unicode).
3
Enter test string
Paste the text you want to match against in the test string field.
4
View matches
All matches are highlighted in the test string and listed below with their index positions and capture group values.
5
Iterate
Refine the pattern and see matches update in real time until the pattern is correct.

Common Use Cases

Backend developers building input validation patterns for email, phone, or ID formats
Data engineers writing regex for log parsing and data extraction pipelines
Frontend developers testing form validation patterns before embedding in code
Security engineers writing WAF rules or detection patterns
DevOps engineers writing grep/sed patterns for log analysis scripts

Key Features

Real-time match highlighting as you type
Full JavaScript regex engine with all flags (g, i, m, s, u)
Capture group display with named group support
Match index and length display
Global match count
Syntax error detection with descriptive messages
100% browser-based — pattern and data never sent to server

🔒

100% Private — No Server Required

All processing happens directly in your browser. No data is uploaded, stored, or transmitted to any server.

Frequently Asked Questions

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Last reviewed on June 1, 2026 by the AiTechWorlds Tools Team. All processing runs locally in your browser.

Learn more on this topic

BookRegular Expressions (Regex) Guide

AiTechWorlds

What is Regex Tester?

How to Use

Enter your regex pattern

Type your regular expression in the pattern field. Syntax errors are highlighted immediately.

Set flags

Toggle flags: g (global), i (case-insensitive), m (multiline), s (dotAll), u (unicode).

Enter test string

Paste the text you want to match against in the test string field.

View matches

All matches are highlighted in the test string and listed below with their index positions and capture group values.

Iterate

Refine the pattern and see matches update in real time until the pattern is correct.

Common Use Cases

Backend developers building input validation patterns for email, phone, or ID formats

Data engineers writing regex for log parsing and data extraction pipelines

Frontend developers testing form validation patterns before embedding in code

Security engineers writing WAF rules or detection patterns

DevOps engineers writing grep/sed patterns for log analysis scripts

Key Features

Real-time match highlighting as you type

Full JavaScript regex engine with all flags (g, i, m, s, u)

Capture group display with named group support

Match index and length display

Global match count

Syntax error detection with descriptive messages

100% browser-based — pattern and data never sent to server