Regular Expressions 101

Pro

^start of line

Negative Lookahead(?!.*\h\S)

.*any character (except for line terminators), repeated any number of times

\hany horizontal whitespace character

\Sany non-whitespace character

Character Class[\da-zA-Z\h]{12}

{12}matches exactly 12 characters from the set below:

\da digit

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

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

\hany horizontal whitespace character

$end of line

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

^(?!.*\h\S)[\da-zA-Z\h]{12}$

New

abcdef12345 
abcdef1234  
abcdef123456
abcdef 23456
 abcdef12345
abcdef12345

abcdef12345 
abcdef1234  
abcdef123456
abcdef 23456
 abcdef12345
abcdef12345