Regular Expressions 101

Pro

^start of line

Non-Capturing Group(?:\d{2})?

?repeats the group contents below at most once:

\d{2}a Unicode decimal digit, repeated exactly 2 times

Character Class[a-z]

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

Character Class[.]

.the literal . (46₁₀ / 56₈ / 2E₁₆)

Character Class[a-z]+

+matches at least one character from the set below:

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

^(?:\d{2})?[a-z][.][a-z]+$

New

a.bcde
12a.bcde

a.bcdefghi
45z.yxwu
"

Invalid Strings: 
1a.bcdef
12a.bcde@