Regular Expressions 101

^start of line

Negative Lookahead(?!.*\[\s*\])

.*any Unicode character (except for line terminators), repeated any number of times

\[the literal [ (91₁₀ / 133₈ / 5B₁₆)

\s*a Unicode whitespace character, repeated any number of times

\]the literal ] (93₁₀ / 135₈ / 5D₁₆)

Character Class[a-zA-Z0-9_\-\[\] ]*

*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)

0-9one character from 0 (48₁₀) to 9 (57₁₀)

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

\[the literal [ (91₁₀ / 133₈ / 5B₁₆)

\]the literal ] (93₁₀ / 135₈ / 5D₁₆)

the literal (32₁₀ / 40₈ / 20₁₆)

$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

^(?!.*\[\s*\])[a-zA-Z0-9_\-\[\] ]*$

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