Regular Expressions Cookbook, 2nd Edition

8.7. Validating Generic URLs

Problem

You want to check whether a given piece of text is a valid URL according to RFC 3986.

Solution

\A
(# Scheme
 [a-z][a-z0-9+\-.]*:
 (# Authority & path
  //
  ([a-z0-9\-._~%!$&'()*+,;=]+@)?              # User
  ([a-z0-9\-._~%]+                            # Named host
  |\[[a-f0-9:.]+\]                            # IPv6 host
  |\[v[a-f0-9][a-z0-9\-._~%!$&'()*+,;=:]+\])  # IPvFuture host
  (:[0-9]+)?                                  # Port
  (/[a-z0-9\-._~%!$&'()*+,;=:@]+)*/?          # Path
 |# Path without authority
  (/?[a-z0-9\-._~%!$&'()*+,;=:@]+(/[a-z0-9\-._~%!$&'()*+,;=:@]+)*/?)?
 )
|# Relative URL (no scheme or authority)
 (# Relative path
  [a-z0-9\-._~%!$&'()*+,;=@]+(/[a-z0-9\-._~%!$&'()*+,;=:@]+)*/?
 |# Absolute path
  (/[a-z0-9\-._~%!$&'()*+,;=:@]+)+/?
 )
)
# Query
(\?[a-z0-9\-._~%!$&'()*+,;=:@/?]*)?
# Fragment
(\#[a-z0-9\-._~%!$&'()*+,;=:@/?]*)?
\Z

Regex options: Free-spacing, case insensitive

Regex flavors: .NET, Java, PCRE, Perl, Python, Ruby

\A (# Scheme (?<scheme>[a-z][a-z0-9+\-.]*): (# Authority & path // (?<user>[a-z0-9\-._~%!$&'()*+,;=]+@)? # User (?<host>[a-z0-9\-._~%]+ # Named host | \[[a-f0-9:.]+\] # IPv6 host | \[v[a-f0-9][a-z0-9\-._~%!$&'()*+,;=:]+\]) # IPvFuture host (?<port>:[0-9]+)? # Port (?<path>(/[a-z0-9\-._~%!$&'()*+,;=:@]+)*/?) # Path |# Path without authority (?<path>/?[a-z0-9\-._~%!$&'()*+,;=:@]+ (/[a-z0-9\-._~%!$&'()*+,;=:@]+)*/?)? ) |# Relative URL (no scheme or authority) (?<path> # Relative path [a-z0-9\-._~%!$&'()*+,;=@]+(/[a-z0-9\-._~%!$&'()*+,;=:@]+)*/? |# Absolute path (/[a-z0-9\-._~%!$&'()*+,;=:@]+)+/? ) ) # Query (?<query>\?[a-z0-9\-._~%!$&'()*+,;=:@/?]*)? ...