The Ultimate Regex Cheat Sheet for 2026

Regular expressions are one of the most powerful tools in a developer's toolkit. Here are the patterns you will actually use.

Email Validation

^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

Matches standard email formats. Not RFC 5322 compliant (nothing is), but catches 99% of real emails.

URL Matching

https?://[^\s/$.?#].[^\s]*

Matches HTTP and HTTPS URLs in text. Simple but effective for most extraction tasks.

IPv4 Address

\b(?:\d{1,3}\.){3}\d{1,3}\b

Matches IP addresses. Does not validate ranges (255 max) — add that logic in code.

Date Formats

\d{4}-\d{2}-\d{2} matches ISO dates (2026-01-15). \d{2}/\d{2}/\d{4} matches US dates (01/15/2026).

Password Strength

^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{8,}$

Requires: lowercase, uppercase, digit, special character, 8+ length.

JSON Key Extraction

"([^"]+)"\s*: extracts all keys from a JSON string.

Log Timestamp

\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2} matches ISO 8601 timestamps in log files.

Test all of these in our Regex Tester — paste the pattern, add your test string, and see matches highlighted in real-time.