regex101: PCRE (Legacy) Match Workspace

Pro

\ban ASCII word boundary

Character Class[A-Z]{2}

{2}matches exactly 2 characters from the set below:

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

Character Class[0-9]{2}

{2}matches exactly 2 characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Non-Capturing Group(?:[ ]?[0-9]{4}){4}

{4}repeats the group contents below exactly 4 times:

Character Class[ ]?

?matches at most one character from the set below:

the literal (32₁₀ / 40₈ / 20₁₆)

Character Class[0-9]{4}

{4}matches exactly 4 characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Negative Lookahead(?!(?:[ ]?[0-9]){3})

Non-Capturing Group(?:[ ]?[0-9]){3}

{3}repeats the group contents below exactly 3 times:

Character Class[ ]?

?matches at most one character from the set below:

the literal (32₁₀ / 40₈ / 20₁₆)

Character Class[0-9]

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Non-Capturing Group(?:[ ]?[0-9]{1,2})?

?repeats the group contents below at most once:

Character Class[ ]?

?matches at most one character from the set below:

the literal (32₁₀ / 40₈ / 20₁₆)

Character Class[0-9]{1,2}

{1,2}matches between 1 and 2 characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

\ban ASCII word boundary

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

25 tokens

Regular Expression

\b[A-Z]{2}[0-9]{2}(?:[ ]?[0-9]{4}){4}(?!(?:[ ]?[0-9]){3})(?:[ ]?[0-9]{1,2})?\b

New

This IBAN looks ok AB12 1234 1234 1234 1234 at first glance
Also this AB12 1234 1234 1234 1234 1 seems fine
And AB12 1234 1234 1234 1234 12 passes


Or without spaces AB123456789012345678
We'll find this AB1234567890123456789 also
Even the longer AB12345678901234567890 matches

Not allowed
------------
AB12 1234 1234 1234 123 (to few numbers)
AB12 1234 1234 1234 1234 123 (to many numbers) 
1234 1234 1234 1234 1234 (starts with numbers)

Extraction

This IBAN looks ok AB12 1234 1234 1234 1234 at first glance
Also this AB12 1234 1234 1234 1234 1 seems fine
And AB12 1234 1234 1234 1234 12 passes


Or without spaces AB123456789012345678
We'll find this AB1234567890123456789 also
Even the longer AB12345678901234567890 matches

Not allowed
------------
AB12 1234 1234 1234 123 (to few numbers)
AB12 1234 1234 1234 1234 123 (to many numbers) 
1234 1234 1234 1234 1234 (starts with numbers)