Regex Tester
Test regular expressions with live matching, capture groups, and replacement. All client-side — nothing leaves your browser.
(\d{1,3}\.) {3}capturing group— {3}\d {1,3}digit [0-9]— {1,3}\.escaped '.'\d {1,3}digit [0-9]— {1,3}No matches found.
What Are Regular Expressions?
Regular expressions (regex) are patterns used to match character combinations in strings. They are a powerful tool built into nearly every programming language, text editor, and CLI tool. From grep and sed to nginx rewrite rules and log parsing pipelines, regex is an essential DevOps skill.
Regex in DevOps & SysAdmin
Common use cases where regular expressions save hours of work:
- Log parsing — extract IPs, timestamps, error codes from log files with
grep -Porawk - Nginx/Apache rewrites — URL rewriting with capture groups in
location ~blocks - Input validation — validate email, IP, domain, UUID formats in scripts and configs
- Text processing — batch rename files, transform CSV, clean data with
sed - Monitoring & alerting — pattern-match log lines in Prometheus, Loki, or ELK stack
Common Regex Patterns for Ops
| Pattern | Matches | Use Case |
|---|---|---|
| \d{1,3}(\.\d{1,3}){3} | IPv4 addresses | Log parsing, firewall rules |
| HTTP/\d\.\d"\s(\d{3}) | HTTP status codes | Access log analysis |
| \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2} | ISO 8601 timestamps | Log correlation |
| ^(ERROR|WARN|FATAL) | Error-level lines | Alert filtering |
Privacy-First Design
This regex tester runs entirely in your browser using the native JavaScript RegExp engine. Your patterns and test strings never leave your machine — no server calls, no telemetry, no storage. Perfect for testing regex against sensitive log data or configuration values.