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Regex Tutorial for Beginners — Learn Regular Expressions
Regex is one of the most powerful — and misunderstood — tools in programming. Once you understand the basic building blocks, you can write patterns that match virtually any text.
Regex Quick Reference
| Pattern | Matches |
|---|---|
. | Any character except newline |
\d | Any digit (0–9) |
\w | Word character (letter, digit, underscore) |
\s | Whitespace (space, tab, newline) |
^ | Start of string |
$ | End of string |
* | Zero or more of previous |
+ | One or more of previous |
? | Zero or one (optional) |
{3} | Exactly 3 of previous |
[abc] | One of a, b, or c |
[^abc] | Any character except a, b, c |
(cat|dog) | Either "cat" or "dog" |
Common Regex Patterns
| Pattern | What It Validates |
|---|---|
^\d{5}$ | US ZIP code (5 digits) |
^\d{4}-\d{2}-\d{2}$ | Date in YYYY-MM-DD format |
^[a-zA-Z0-9]+$ | Alphanumeric string |
https?://\S+ | HTTP or HTTPS URL |
\b\w{8,}\b | Words with 8+ characters |
Frequently Asked Questions
A pattern syntax for searching, matching, or replacing text. Supported in all major programming languages and many text editors.
The dot matches any character; the asterisk means zero or more repetitions. Together .* matches any string of any length (greedy, including empty).
Basic pattern: ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$. For production, consider a dedicated email validation library for full RFC compliance.
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