Regular Expressions 101

^start of line

-?optionally matches the literal - (45₁₀ / 55₈ / 2D₁₆)

Negative Lookahead(?!.{12})

.{12}any character (except for line terminators), repeated exactly 12 times

\d+a digit, repeated at least once

Non-Capturing Group(?:\.\d+)?

?repeats the group contents below at most once:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d+a digit, repeated at least once

$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.

Search reference

Regular Expression

^-?(?!.{12})\d+(?:\.\d+)?$

New

66666666666
-66666666666
.6666666666
6.666666666
66.66666666
666.6666666
6666.666666
66666.66666
666666.6666
6666666.666
66666666.66
666666666.6
6666666666.
6666666.6666