File compression can both assist and hinder accessibility. Smaller files (75% compression is not uncommon) are faster to download -- a major concern for users with slower Internet connections. On the other hand, compressed files may require special software to extract the information.
If providing information in a compressed format, the state agency must also adhere to the following:
- For compressed files, do at least one of the following:
- Provide an alternative, uncompressed file to download, or
- Provide a self-extracting file (requiring no third-party software). Keep in mind that some users may not wish to download executable (.exe) files due to security concerns.
- Provide links to decompression utilities. Ensure that the agency has a license that allows distribution or that the utility is "freeware." Note: The requirement for a decompression utility reduces accessibility.
- Provide and prominently display a link to the web accessibility statement, which provides contact information for obtaining assistance in working with a compressed file. For more information refer to Section 6.
Note: Single, small files (less than 35 KB) should never be compressed since the time saved downloading may not be worth the need for special software.
Perform a manual check.