Regular Expressions 101

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/
\b(?:(?:https?|ftp):\/\/)(?:\S+(?::\S*)?@)?(?:(?!10(?:\.\d{1,3}){3})(?!127(?:\.\d{1,3}){3})(?!169\.254(?:\.\d{1,3}){2})(?!192\.168(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[+a-z\x{00a1}-\x{ffff}0-9]-?)*[+a-z\x{00a1}-\x{ffff}0-9])(?:\.(?:[+a-z\x{00a1}-\x{ffff}0-9]-?)*[+a-z\x{00a1}-\x{ffff}0-9])*(?:\.(?:[{2,}a-z\x{00a1}-\x{ffff}])))(?::\d{2,5})?(?:\/[^*\s])?\b
/
gi
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
Non-capturing group
(?:(?:https?|ftp):\/\/)
Non-capturing group
(?:https?|ftp)
1st Alternative
https?
http matches the characters http literally (case insensitive)
s
matches the character s literally (case insensitive)
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
2nd Alternative
ftp
ftp matches the characters ftp literally (case insensitive)
: matches the character : literally (case insensitive)
\/ matches the character / literally (case insensitive)
\/ matches the character / literally (case insensitive)
Non-capturing group
(?:\S+(?::\S*)?@)?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\S
matches any non-whitespace character (equivalent to [^\r\n\t\f\v ])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
Non-capturing group
(?::\S*)?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
: matches the character : literally (case insensitive)
\S
matches any non-whitespace character (equivalent to [^\r\n\t\f\v ])
@ matches the character @ literally (case insensitive)
Non-capturing group
(?:(?!10(?:\.\d{1,3}){3})(?!127(?:\.\d{1,3}){3})(?!169\.254(?:\.\d{1,3}){2})(?!192\.168(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[+a-z\x{00a1}-\x{ffff}0-9]-?)*[+a-z\x{00a1}-\x{ffff}0-9])(?:\.(?:[+a-z\x{00a1}-\x{ffff}0-9]-?)*[+a-z\x{00a1}-\x{ffff}0-9])*(?:\.(?:[{2,}a-z\x{00a1}-\x{ffff}])))
1st Alternative
(?!10(?:\.\d{1,3}){3})(?!127(?:\.\d{1,3}){3})(?!169\.254(?:\.\d{1,3}){2})(?!192\.168(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))
Negative Lookahead
(?!10(?:\.\d{1,3}){3})
Assert that the Regex below does not match
10 matches the characters 10 literally (case insensitive)
Non-capturing group
(?:\.\d{1,3}){3}
{3} matches the previous token exactly 3 times
\. matches the character . literally (case insensitive)
\d
matches a digit (equivalent to [0-9])
Negative Lookahead
(?!127(?:\.\d{1,3}){3})
Assert that the Regex below does not match
127 matches the characters 127 literally (case insensitive)
Non-capturing group
(?:\.\d{1,3}){3}
Negative Lookahead
(?!169\.254(?:\.\d{1,3}){2})
Assert that the Regex below does not match
169 matches the characters 169 literally (case insensitive)
\. matches the character . literally (case insensitive)
254 matches the characters 254 literally (case insensitive)
Non-capturing group
(?:\.\d{1,3}){2}
Negative Lookahead
(?!192\.168(?:\.\d{1,3}){2})
Assert that the Regex below does not match
192 matches the characters 192 literally (case insensitive)
\. matches the character . literally (case insensitive)
168 matches the characters 168 literally (case insensitive)
Non-capturing group
(?:\.\d{1,3}){2}
Negative Lookahead
(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})
Assert that the Regex below does not match
Non-capturing group
(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])
Non-capturing group
(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}
Non-capturing group
(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))
2nd Alternative
(?:(?:[+a-z\x{00a1}-\x{ffff}0-9]-?)*[+a-z\x{00a1}-\x{ffff}0-9])(?:\.(?:[+a-z\x{00a1}-\x{ffff}0-9]-?)*[+a-z\x{00a1}-\x{ffff}0-9])*(?:\.(?:[{2,}a-z\x{00a1}-\x{ffff}]))
Non-capturing group
(?:(?:[+a-z\x{00a1}-\x{ffff}0-9]-?)*[+a-z\x{00a1}-\x{ffff}0-9])
Non-capturing group
(?:[+a-z\x{00a1}-\x{ffff}0-9]-?)*
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[a-z\x{00a1}-\x{ffff}0-9]
-
matches the character - literally (case insensitive)
Match a single character present in the list below
[a-z\x{00a1}-\x{ffff}0-9]
Non-capturing group
(?:\.(?:[+a-z\x{00a1}-\x{ffff}0-9]-?)*[+a-z\x{00a1}-\x{ffff}0-9])*
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . literally (case insensitive)
Non-capturing group
(?:[+a-z\x{00a1}-\x{ffff}0-9]-?)*
Match a single character present in the list below
[a-z\x{00a1}-\x{ffff}0-9]
Non-capturing group
(?:\.(?:[{2,}a-z\x{00a1}-\x{ffff}]))
\. matches the character . literally (case insensitive)
Non-capturing group
(?:[{2,}a-z\x{00a1}-\x{ffff}])
Non-capturing group
(?::\d{2,5})?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
: matches the character : literally (case insensitive)
\d
matches a digit (equivalent to [0-9])
{2,5} matches the previous token between 2 and 5 times, as many times as possible, giving back as needed (greedy)
Non-capturing group
(?:\/[^*\s])?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\/ matches the character / literally (case insensitive)
Match a single character not present in the list below
[^\s]
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
Global pattern flags
g modifier: global. All matches (don't return after first match)
i modifier: insensitive. Case insensitive match (ignores case of [a-zA-Z])
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gi

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