"Free Regex Tester REST API — Test, Match, Replace & Explain Patterns via HTTP"

#api #regex #webdev #productivity

Stop Copy-Pasting Between regex101 and Your Code

We've all been there: open regex101, test a pattern, copy it back, escape the backslashes, test again. What if your code could test regex patterns via a simple API call?

Regex Tester API

A free REST API that lets you:

Match patterns against text and get all groups
Replace text using regex substitution
Explain patterns in plain English

Match Example

curl -X POST "https://regex-tester-api.p.rapidapi.com/match" \
  -H "Content-Type: application/json" \
  -d '{
    "pattern": "(\\d{4})-(\\d{2})-(\\d{2})",
    "text": "Today is 2026-04-08 and tomorrow is 2026-04-09",
    "flags": "g"
  }'

Response:

{
  "matches": [
    {
      "match": "2026-04-08",
      "groups": ["2026", "04", "08"],
      "index": 9
    },
    {
      "match": "2026-04-09",
      "groups": ["2026", "04", "09"],
      "index": 37
    }
  ],
  "count": 2
}

Explain Example

curl -X POST "https://regex-tester-api.p.rapidapi.com/explain" \
  -d '{"pattern": "^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$"}'

Returns a human-readable breakdown of each part of the pattern — great for code reviews and documentation.

Use Cases

CI/CD validation: Test regex patterns in your pipeline before deploying
Code review: Auto-explain complex patterns in PR comments
Learning: Understand regex patterns you found on Stack Overflow
Multi-language: Use the same patterns from Python, Go, Ruby — not just JavaScript