Regular Expressions 101

Pro

^start of line

Negative Lookahead(?!00)

00the literal text 00

\d{1,4}a digit, repeated between 1 and 4 times

Non-Capturing Group(?:\.\d{1,4}[aAxX]?)?

?repeats the group contents below at most once:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,4}a digit, repeated between 1 and 4 times

Character Class[aAxX]?

?matches at most one character from the set below:

athe literal a (97₁₀ / 141₈ / 61₁₆) (case sensitive)

Athe literal A (65₁₀ / 101₈ / 41₁₆) (case sensitive)

xthe literal x (120₁₀ / 170₈ / 78₁₆) (case sensitive)

Xthe literal X (88₁₀ / 130₈ / 58₁₆) (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

^(?!00)\d{1,4}(?:\.\d{1,4}[aAxX]?)?$

New

Examples to pass:
0.2345X
1.23A
7300.3211x
0.1a
0.01
Examples to fail:
a.123
00.43x

Examples to pass:
0.2345X
1.23A
7300.3211x
0.1a
0.01
Examples to fail:
a.123
00.43x