Regex Tester

Regex Tester | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Development
Input types: text, textarea, checkbox
Output type: text
Sample coverage: 4
API ready: Yes

Overview

The Regex Tester is a streamlined utility designed to help developers and data analysts validate regular expression patterns against sample text in real-time. By providing an immediate visual breakdown of matches, groups, and flags, this tool ensures your regex logic is accurate before you implement it in your codebase.

When to use

Validating complex search patterns for data extraction or text processing tasks.
Debugging regex syntax errors when your application fails to capture expected strings.
Testing how different regex flags, such as global or case-insensitive, affect your matching results.

How it works

1Enter your regular expression pattern into the Regex Pattern field.
2Input the target text you wish to analyze in the Test Text area.
3Apply optional flags like 'g', 'i', or 'm' to refine your search behavior.
4View the highlighted matches and capture groups instantly to verify your logic.

Use cases

Extracting email addresses or phone numbers from unstructured log files.
Validating user input formats like dates, postal codes, or usernames.
Refactoring large blocks of text by identifying specific patterns for replacement.

Examples

1. Extracting Email Addresses

Data Analyst

Background

A large list of customer feedback contains mixed contact information.

Problem

Need to isolate all email addresses from a messy text block.

How to use

Paste the text into the Test Text field and use the pattern [a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}.

flags: g

Outcome

The tool highlights every valid email address found within the text block.

2. Validating Date Formats

Web Developer

Background

Building a form that requires a specific YYYY-MM-DD date format.

Problem

Ensuring the regex correctly identifies valid dates while rejecting invalid ones.

How to use

Enter the pattern ^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01])$ and test against various date strings.

flags: g

Outcome

FAQ

What regex engine does this tool use?

This tool utilizes the standard JavaScript RegExp engine, which is compatible with most modern web browsers and Node.js environments.

Can I use capture groups in my patterns?

Yes, the tool supports standard capture groups, and you can view the captured content in the results output.

What do the flags 'g', 'i', and 'm' do?

'g' enables global matching, 'i' makes the search case-insensitive, and 'm' enables multiline mode.

Is my data stored on your servers?

No, all regex testing is performed locally in your browser, ensuring your input text remains private.

Why is my regex not matching anything?

Check for syntax errors, ensure your flags are correct, and verify that your pattern logic matches the structure of your test text.

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Examples that match this tool

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Inputs

Result

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Extracting Email Addresses

2. Validating Date Formats

FAQ

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