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Regular Expression
Test String
Substitution
Hostname FQDN validation
This is a version that works in javascript (without regex look behind). Hostnames are composed of a series of labels concatenated with dots. Each label is 1 to 63 characters long, and may contain: the ASCII letters a-z and A-Z, the digits 0-9, and the hyphen ('-'). Additionally: labels cannot start or end with hyphens (RFC 952) labels can start with numbers (RFC 1123) trailing dot is not allowed max length of ascii hostname including dots is 253 characters TLD (last label) is at least 2 characters and only ASCII letters we want at least 1 level above TLD Source: https://stackoverflow.com/questions/11809631/fully-qualified-domain-name-validation, answer from JdeBPComments
Top Regular Expressions
Url checker with or without http:// or https://
Match string not containing string
Check if a string only contains numbers
Only letters and numbers
Match elements of a url
date format (yyyy-mm-dd)
Url Validation Regex | Regular Expression - Taha
Match an email address
Validate an ip address
nginx test
Extract String Between Two STRINGS
special characters check
match whole word
Match anything enclosed by square brackets.
Match or Validate phone number
Match html tag
Find Substring within a string that begins and ends with paranthesis
Simple date dd/mm/yyyy
Blocking site with unblocked games
Match dates (M/D/YY, M/D/YYY, MM/DD/YY, MM/DD/YYYY)
Match string not containing string
Check if a string only contains numbers
Only letters and numbers
Match elements of a url
date format (yyyy-mm-dd)
Url Validation Regex | Regular Expression - Taha
Match an email address
Validate an ip address
nginx test
Extract String Between Two STRINGS
special characters check
match whole word
Match anything enclosed by square brackets.
Match or Validate phone number
Match html tag
Find Substring within a string that begins and ends with paranthesis
Simple date dd/mm/yyyy
Blocking site with unblocked games
Match dates (M/D/YY, M/D/YYY, MM/DD/YY, MM/DD/YYYY)
Cheat Sheet
| Character classes | |
|---|---|
| . | any character except newline |
| \w \d \s | word, digit, whitespace |
| \W \D \S | not word, digit, whitespace |
| [abc] | any of a, b, or c |
| [^abc] | not a, b, or c |
| [a-g] | character between a & g |
| Anchors | |
| ^abc$ | start / end of the string |
| \b | word boundary |
| Escaped characters | |
| \. \* \\ | escaped special characters |
| \t \n \r | tab, linefeed, carriage return |
| \u00A9 | unicode escaped © |
| Groups & Lookaround | |
| (abc) | capture group |
| \1 | backreference to group #1 |
| (?:abc) | non-capturing group |
| (?=abc) | positive lookahead |
| (?!abc) | negative lookahead |
| Quantifiers & Alternation | |
| a* a+ a? | 0 or more, 1 or more, 0 or 1 |
| a{5} a{2,} | exactly five, two or more |
| a{1,3} | between one & three |
| a+? a{2,}? | match as few as possible |
| ab|cd | match ab or cd |
