Regular Expressions 101

Explanation

Pro

^start of line

Negative Lookahead(?![\d.-])

Character Class[\d.-]

\da digit

.the literal . (46₁₀ / 56₈ / 2E₁₆)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-zA-Z\d.-]{0,23}

{0,23}matches between 0 and 23 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

.the literal . (46₁₀ / 56₈ / 2E₁₆)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-zA-Z\d]

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

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

^(?![\d.-])[a-zA-Z\d.-]{0,23}[a-zA-Z\d]$

New

a12345678901234567891234
a1234567890123456789123-

a12345678901234567891234
a1234567890123456789123-