Work Offline in Firefox
Whether or not offline mode is an antiquated feature, it is still included in Firefox as Work Offline under the File menu. So how does Firefox work offline?
Once Work Offline is activated, Firefox does not use an Internet connection to open web pages. Instead, it uses copies of web pages that have been cached, or saved, on your computer. These caches are typically copies of the last time you visited a particular page, and most of the web page elements, such as text and images, will be available.
There are some very good uses for using Work Offline in Firefox. For instance, a laptop computer uses significantly more power when its wireless radio is turned on. By turning the radio off, you can read web pages that you've recently visited in Firefox without the additional battery drain. In another case, if your Internet connection has been interrupted, you can work offline if you simply wanted to revisit a page you have recently accessed.
Since Work Offline is based on Internet cache, it has serious limitations. You can only view pages that have been accessed by your computer and stored in cache. If you have recently cleared your cache, or it has been a while since you visited a particular page, it may no longer be available in offline mode. Additionally, Firefox's Work Offline mode is read-only; in other words, you are not able to fill out forms, play browser-based games, or interact with dynamic media. As such, some features on web pages may not work as expected.