Domain masking or URL masking is the act of hiding the actual domain name of a website from the URL field of a user's web browser in favor of another name. There are many ways to do this, including the following examples.
- HTML inline frame or frameset so a frame embedded in the main website actually points to some other site.
- URL rewriting (e.g., mod_rewrite) or aliases to have the web server serve the same page for two different domain names.
- Virtual hosting whereby the HTTP server serves up several different websites based only upon the content of the "Host" HTTP Request Header.
Once the URL is masked it displays the URL mask rather than the original URL/domain name. Masking does not affect the content of the actual website; it only covers up the original URL/domain name. Domain masking prevents users from being able to see the actual domain website, whether it be due to length or privacy/security issues.