What is the difference between a URI, a URL and a URN?

Question

People talk about URLs, URIs, and URNs as if they\'re different things, but they look the same to the naked eye.

W

Answer 1

Identity = Name with Location

Every URL(Uniform Resource Locator) is a URI(Uniform Resource Identifier), abstractly speaking, but every URI is not a URL. There is another subcategory of URI is URN (Uniform Resource Name), which is a named resource but do not specify how to locate them, like mailto, news, ISBN is URIs. Source

URN:

• URN Format : urn:[namespace identifier]:[namespace specific string]
• urn: and : stand for themselves.
• Examples:
  • urn:uuid:6e8bc430-9c3a-11d9-9669-0800200c9a66
  • urn:ISSN:0167-6423
  • urn:isbn:096139210x
  • Amazon Resource Names (ARNs) is a uniquely identify AWS resources.
    • ARN Format : arn:partition:service:region:account-id:resource

URL:

• URL Format : [scheme]://[Domain][Port]/[path]?[queryString]#[fragmentId]
• :,//,? and # stand for themselves.
• schemes are https,ftp,gopher,mailto,news,telnet,file,man,info,whatis,ldap...
• Examples:
  • http://ip_server/path?query
  • ftp://ip_server/path
  • mailto:email-address
  • news:newsgroup-name
  • telnet://ip_server/
  • file://ip_server/path_segments
  • ldap://hostport/dn?attributes?scope?filter?extensions

Analogy:
To reach a person: Driving(protocol others SMS, email, phone), Address(hostname other phone-number, emailid) and person name(object name with a relative path).