What is the regex to match a string not containing more than x consecutive characters

Question

I want to match strings that do not contain more than 3 of the same character repeated in a row. So:

• abaaaa [no match]
• abawdasd [match]
• abbbbasda

Answer 1

Use a negative lookahead with back references:

^(?:(.)(?!\1\1))*$

See live demo using your examples.

(.) captures each character in group 1 and the negative look ahead asserts that the next 2 chars are not repeats of the captured character.