What is the difference between URI URL and URN

Question

What s the difference between an URI  URL and URN  I have read a lot of sites  even Wikipedia  but I don t understand it   URI  http   www foo com bar html URL  http   www foo com bar html URN  bar html  Is this correct

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Below I sum up Prateek Joshi s awesome explanation   The theory    URI  uniform resource identifier  identifies a resource  text document  image file  etc  URL  uniform resource locator  is a subset of the URIs that include a network location URN  uniform resource name  is a subset of URIs that include a name within a given space  but no location   That is     And for an example     Also  if you haven t already  I suggest reading Roger Pate s answer

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URL -- Uniform Resource Locator  Contains information about how to fetch a resource from its location   For example    http   example com mypage html ftp   example com download zip mailto user example com file    home user file txt http   example com resource foo bar fragment  other link html  A relative URL  only useful in the context of another URL    URLs always start with a protocol  http  and usually contain information such as the network host name  example com  and often a document path   foo mypage html   URLs may have query parameters and fragment identifiers   URN -- Uniform Resource Name  Identifies a resource by name    It always starts with the prefix urn   For example    urn isbn 0451450523 to identify a book by its ISBN number  urn uuid 6e8bc430-9c3a-11d9-9669-0800200c9a66 a globally unique identifier urn publishing book - An XML namespace that identifies the document as a type of book    URNs can identify ideas and concepts   They are not restricted to identifying documents    When a URN does represent a document  it can be translated into a URL by a  resolver    The document can then be downloaded from the URL   URI -- Uniform Resource Identifier  URIs encompasses both URLs  URNs  and other ways to indicate a resource   An example of a URI that is neither a URL nor a URN would be a data URI such as data  Hello 20World   It is not a URL or URN because the URI contains the data   It neither names it  nor tells you how to locate it over the network   There are also uniform resource citations  URCs  that point to meta data about a document rather than to the document itself   An example of a URC would be an indicator for viewing the source code of a web page  view-source http   example com    A URC is another type of URI that is neither URL nor URN   Frequently Asked Questions  I ve heard that I shouldn t say URL anymore  why   The w3 spec for HTML says that the href of an anchor tag can contain a URI  not just a URL   You should be able to put in a URN such as  lt a href  urn isbn 0451450523  gt    Your browser would then resolve that URN to a URL and download the book for you   Do any browsers actually know how to fetch documents by URN   Not that I know of  but modern web browser do implement the data URI scheme   Can a URI be both a URL and a URN   Good question   I ve seen lots of places on the web that state this is true    I haven t been able to find any examples of something that is both a URL and a URN   I don t see how it is possible because a URN starts with urn  which is not a valid network protocol   Does the difference between URL and URI have anything to do with whether it is relative or absolute   No    Both relative and absolute URLs are URLs  and URIs    Does the difference between URL and URI have anything to do with whether it has query parameters   No    Both URLs with and without query parameters are URLs  and URIs    Does the difference between URL and URI have anything to do with whether it has a fragment identifier   No    Both URLs with and without fragment identifiers are URLs  and URIs    Is a tel  URI a URL or a URN   For example tel 1-800-555-5555  It doesn t start with urn  and it has a protocol for reaching a resource over a network    It must be a URL   But doesn t the w3C now say that URLs and URIs are the same thing   Yes   The W3C realized that there is a ton of confusion about this   They issued a URI clarification document that says that it is now OK to use URL and URI interchangeably   It is no longer useful to strictly segment URIs into different types such as URL  URN  and URC

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URI  Uniform Resource Identifier  according to Wikipedia      a string of characters used to identify a resource    URL  Uniform Resource Locator  is a URI that implies an interaction mechanism with resource  for example https   www google com specifies the use of HTTP as the interaction mechanism  Not all URIs need to convey interaction-specific information   URN  Uniform Resource Name  is a specific form of URI that has urn as it s scheme  For more information about the general form of a URI refer to https   en wikipedia org wiki Uniform Resource Identifier Syntax  IRI  International Resource Identifier  is a revision to the definition of URI that allows us to use international characters in URIs

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Uniform Resource Identifier  URI  is a string of characters used to identify a name or a resource on the Internet  A URI identifies a resource either by location  or a name  or both  A URI has two specializations known as URL and URN   A Uniform Resource Locator  URL  is a subset of the Uniform Resource Identifier  URI  that specifies where an identified resource is available and the mechanism for retrieving it  A URL defines how the resource can be obtained  It does not have to be HTTP URL  http      a URL can also be  ftp     or  smb       A Uniform Resource Name  URN  is a Uniform Resource Identifier  URI  that uses the URN scheme  and does not imply availability of the identified resource  Both URNs  names  and URLs  locators  are URIs  and a particular URI may be both a name and a locator at the same time   The URNs are part of a larger Internet information architecture which is composed of URNs  URCs and URLs   bar html is not a URN  A URN is similar to a person s name  while a URL is like a street address  The URN defines something s identity  while the URL provides a location  Essentially   what  vs   where   A URN has to be of this form  lt URN gt       urn    lt NID gt       lt NSS gt  where  lt NID gt  is the Namespace Identifier  and  lt NSS gt  is the Namespace Specific String   To put it differently         A URL is a URI that identifies a resource and also provides the means of locating the resource by describing the way to access it   A URL is a URI   A URI is not necessarily a URL      I d say the only thing left to make it 100  clear would be to have an example of an URI that is not an URL  We can use the examples in the RFC3986   URL  ftp   ftp is co za rfc rfc1808 txt URL  http   www ietf org rfc rfc2396 txt URL  ldap    2001 db8  7  c GB objectClass one URL  mailto John Doe example com URL  news comp infosystems www servers unix URL  telnet   192 0 2 16 80  URN  not URL   urn oasis names specification docbook dtd xml 4 1 2 URN  not URL   tel  1-816-555-1212       Also check this out - https   quintupledev wordpress com 2016 02 29 difference-between-uri-url-and-urn

[http] What is the difference between URI, URL and URN?

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