Linking to non-HTML files
A link to a non-HTML document should provide information about the document, including a meaningful name, the file format and the file size. This gives users a good idea of what to expect if they click on the link.
This information is especially useful in the case of links to non-HTML files, such as image files, PDFs, Microsoft Office or OpenDocument files, and audio or video files.
Usability standard requirements
The New Zealand Government Web Usability Standard requires that links to non-HTML files be accompanied by information indicating the file’s format and size.
Informing users up front about a file's format and size allows them to make an informed decision about whether or not to download it. Should they choose to download it, an indication of what type of application or plugin they will need to use the file is helpful, as is providing an extra link to any plugins needed to use the file.
Providing useful link text as described above can also help screen reader users. Screen reader software typically enables the user to call up a list of all the links on a page for quicker access. Since, in this view, each link is removed from its surrounding page context, it can be difficult to determine the link's purpose if the link text alone does not make the target of the link clear.
When providing information about the format and size for a link to a non-HTML file, the preferred approach is to include that information directly in the link text itself. An alternative approach is to make sure that the information comes immediately before or after the link. For example: