urilocaluncfile-uri

3 or 5 slashes for cross-browser file URI

I am using <a href="file:..."> links inside an Intranet for local folder access.

What bothers me is the amount of slashes I have to write in those URI for cross-browser compatibility.

Internet Explorer 11.904.16299.0

   file://server/share/path/to/file ok
  file:///server/share/path/to/file not working
 file:////server/share/path/to/file ok
file://///server/share/path/to/file ok

Edge 41.16299.820.0

   file://server/share/path/to/file ok
  file:///server/share/path/to/file not working
 file:////server/share/path/to/file ok
file://///server/share/path/to/file ok

Firefox 60.0 with Local Filesystem Links Extension

   file://server/share/path/to/file not working
  file:///server/share/path/to/file not working
 file:////server/share/path/to/file not working
file://///server/share/path/to/file ok

When I look for answers in Stack Overflow or similar, I end up in those posts, saying that the correct amount is 3 slashes.

I write this question and answer it in case someone gets confused like I did.

Solution

  • It is important to distinct 2 types of <a href="file:...>" links: local paths and UNC paths.

    Local path URI

    This is the path to a file accessible inside the client machine, either because the file is inside its local storage or because it is accessible through a mapped drive / mounted folder.

    Those URI take 3 slashes:

    The fourth slash for the second example is the UNIX root /.

    UNC path URI

    The format I show in my question, file://///server/share/path/to/file, is known as an UNC path.

    This is a path accessible from the client machine through an internal URI, like my.server.com. In Windows, for example, this is when you use the server URI to access the file, not its mapped drive letter.

    Those URI take 5 slashes:

    The links that helped me answer my question:

    The "about" section of the Firefox Local Filesystem Links Extension also talks about it: