Regular Expressions 101

Pro

^start of line

Positive Lookahead(?=[a-zA-Z\d]{4,7}$)

Character Class[a-zA-Z\d]{4,7}

{4,7}matches between 4 and 7 characters 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)

\da digit

$end of line

Character Class[a-zA-Z]*

*matches any number of characters 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)

\d{4}a digit, repeated exactly 4 times

Character Class[a-zA-Z]*

*matches any number of characters 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)

$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

^(?=[a-zA-Z\d]{4,7}$)[a-zA-Z]*\d{4}[a-zA-Z]*$

New

abc1234
ab1234
1234
1234abd

 Invalid input: 
1a1234
12345
a1s1234

abc1234
ab1234
1234
1234abd

 Invalid input: 
1a1234
12345
a1s1234