Regular Expressions 101

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/
^wp-content\/uploads\/(?!(2021\/06||2021\/07)\/).+$
/
gm
^ asserts position at start of a line
wp-content
matches the characters wp-content literally (case sensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
uploads
matches the characters uploads literally (case sensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
Negative Lookahead
(?!(2021\/06||2021\/07)\/)
Assert that the Regex below does not match
1st Capturing Group
(2021\/06||2021\/07)
1st Alternative
2021\/06
2021
matches the characters 2021 literally (case sensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
06
matches the characters 06 literally (case sensitive)
2nd Alternative null, matches any position
3rd Alternative
2021\/07
2021
matches the characters 2021 literally (case sensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
07
matches the characters 07 literally (case sensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
.
matches any character (except for line terminators)
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
$ asserts position at the end of a line
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gm

Test String

Code Generator

Generated Code

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Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report.
For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php