How to group without capturing — (?:...)

You need grouping for a quantifier or an alternation, but the extra capture slot would shift everyone's numbers.

Patterns use the syntax shared by PCRE / Python / JavaScript; engine differences are flagged in the cheatsheet where they matter. Test any pattern at regex101.com — and pick the matching engine.

(?:https?://)?[\w.-]+
# optional scheme, not captured — keeps group numbers clean

Regex Cheatsheet one-page card — patterns that actually work — The full one-page card — Regex Cheatsheet. Get the complete cheatsheet on GitHub