Regular Expressions 101

Pro

^start of line

Non-Capturing Group(?:[a-z\d]+-?)*?

*?repeats the group contents below any number of times:

Character Class[a-z\d]+

+matches at least one character from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

\da digit

-?optionally matches the literal - (45₁₀ / 55₈ / 2D₁₆)

Non-Capturing Group(?:/|(?=20\d{2}-?){1,2})

1st Alternative/

/the literal / (47₁₀ / 57₈ / 2F₁₆)

2nd Alternative(?=20\d{2}-?){1,2}

Positive Lookahead(?=20\d{2}-?){1,2}

{1,2}repeats the group contents below between 1 and 2 times:

20the literal text 20

\d{2}a digit, repeated exactly 2 times

-?optionally matches the literal - (45₁₀ / 55₈ / 2D₁₆)

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

25 tokens

Regular Expression

^(?:[a-z\d]+-?)*?(?:/|(?=20\d{2}-?){1,2})

New

abc-def/something/else/ [incl. slash if there is not character before it]
abc-def-2019/something/else/
abc-def-2019-2020/something/else/
abc-def-125-2019/something/else/

Substitution

abc-def/something/else/ [incl. slash if there is not character before it]
abc-def-2019/something/else/
abc-def-2019-2020/something/else/
abc-def-125-2019/something/else/