Regex Tester

//g
Flags:
Test String
343 chars
Match Details
Enter a pattern to start matching

What This Tool Does

Regex Tester is built for deterministic developer and agent workflows.

Test regular expressions with real-time matching, group capture, and replace mode. Common patterns included.

Use How to Use for execution steps and FAQ for constraints, policies, and edge cases.

Last updated:

This tool is provided as-is for convenience. Output should be verified before use in any production or critical context.

Agent Invocation

Best Path For Builders

Dedicated API endpoint

Deterministic outputs, machine-safe contracts, and production-ready examples.

Dedicated API

https://aidevhub.io/api/regex-tester/

OpenAPI: https://aidevhub.io/api/openapi.yaml

GET /api/regex-tester/ Test a regex pattern
POST /api/regex-tester/ Test a regex pattern

Unified Runtime API

https://aidevhub.io/api/tools/run/?toolId=regex-tester&a=...

GET and POST are supported at /api/tools/run/ with identical validation and limits.

Limit: req / s, input max 512 KB.

REST API

Base URL

https://aidevhub.io/api/regex-tester/

50 requests/day per IP. No authentication required. CORS enabled. OpenAPI spec

Endpoints

GET /api/regex-tester/ Test a regex pattern
POST /api/regex-tester/ Test a regex pattern

Example

curl "https://aidevhub.io/api/regex-tester/?pattern=%5Cd%2B&text=abc+123+def+456&flags=g"

Example Response

{
  "valid": true,
  "pattern": "\\d+",
  "matches": [
    {
      "match": "123",
      "index": 4
    }
  ],
  "match_count": 2
}

How to Use Regex Tester

  1. 1

    Enter your regex pattern

    Type a regular expression in the pattern field (e.g., `^[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,}$` for email). Use flags (g, i, m) as needed.

  2. 2

    Input test strings to match against

    Paste or type multiple test strings in the input field. The tool will highlight all matches in real-time as you type.

  3. 3

    View matches and capture groups

    See all matches highlighted with their exact positions. If your pattern has capture groups (parentheses), see the captured values listed separately.

  4. 4

    Check regex explanation

    Read the auto-generated English explanation of what your regex does. This helps you debug patterns or learn regex syntax.

  5. 5

    Test edge cases and iterate

    Add more test strings to cover edge cases (empty strings, special chars, long text). Refine your pattern until all cases pass.

Frequently Asked Questions

What is Regex Tester?
Regex Tester is a real-time regular expression testing tool with instant match highlighting and pattern explanation. It's essential for developers writing, debugging, or learning regex patterns.
How do I use Regex Tester?
Enter your regex pattern in the top field and your test string below. Matches are highlighted in real time. You can set flags like global, case-insensitive, and multiline, and view captured groups for each match.
Is Regex Tester free?
Yes. This tool is free to use with immediate access—no account required.
Does Regex Tester store or send my data?
No. All processing happens entirely in your browser. Your data never leaves your device — nothing is sent to any server.
What regex flavor does this tool support?
This tool uses JavaScript's native RegExp engine, which supports standard regex syntax including character classes, quantifiers, lookahead, lookbehind, named capture groups, and Unicode property escapes.