Types of URLs

Question

1) Absolute
http://www.example.com/images/icons.png

2) Relative
../images/icons.png

3) ???
/images/icons.png

4) ???
//www.example.com/images/icons.png

Do URL types 3 and 4 have a name? One place I've seen type 4 being used is at slashdot.

Answer 1

Type three is root-relative.

Dunno about 4.

Answer 2

number 3 is also considered relative. number 4 is absolute, but lacks the protocol. This is useful, if you want to be able to access the same URL using HTTP and HTTPS.

Absolute URLs specify the location of a Web page in full, and work identically no matter where in the world you are.

Relative URLs are context-sensitive, giving a path with respect to your current location.

Answer 3

1. Absolute http://www.example.com/images/icons.png
2. Document-Relative ../images/icons.png
3. Root-Relative /images/icons.png
4. Protocol-Relative //www.example.com/images/icons.png

For #4, I've also often called them "Protocol-Agnostic"

Answer 4

Type 1 is just a "URI" (sometimes called an "absolute URI").

For types 2, 3 and 4 the definitive answers are in RFC 3986, section 4.2.

They are all "relative references", but according to the RFC are qualified thus:

• ../images/icons.png - relative path reference
• /images/icons.png - absolute path reference
• //.../icons.png - network path reference