Regular Expressions 101

^start of line

Positive Lookahead(?=[a-z\d-]*/)

Character Class[a-z\d-]*

*matches any number of characters from the set below:

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

\da digit

-the literal - (45₁₀ / 55₈ / 2D₁₆)

/the literal / (47₁₀ / 57₈ / 2F₁₆)

Character Class[a-zA-Z013-9-]+

+matches at least one character from the set below:

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

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

3-9one character from 3 (51₁₀) to 9 (57₁₀)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Atomic Group(?>2(?!0(?:19|20)(?!\d))|[a-zA-Z013-9-]+)*

*repeats the group contents below any number of times:

1st Alternative2(?!0(?:19|20)(?!\d))

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Negative Lookahead(?!0(?:19|20)(?!\d))

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

Non-Capturing Group(?:19|20)

1st Alternative19

19the literal text 19

2nd Alternative20

20the literal text 20

Negative Lookahead(?!\d)

\da digit

2nd Alternative[a-zA-Z013-9-]+

Character Class[a-zA-Z013-9-]+

+matches at least one character from the set below:

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

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

3-9one character from 3 (51₁₀) to 9 (57₁₀)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

/?optionally matches the literal / (47₁₀ / 57₈ / 2F₁₆)

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.

Search reference

Regular Expression

^(?=[a-z\d-]*/)[a-zA-Z013-9-]+(?>2(?!0(?:19|20)(?!\d))|[a-zA-Z013-9-]+)*/?

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/
aaa-20199-2019/
aaa
aaa/
aaa2019
aaa2019test/
aaa201aaa2019aaa2019/

Regular Expression

Extraction