Understanding browsing modes

Ad Annihilator features its own, improved cache. It is able to retrieve documents from cache rather than from Internet when necessary to speed up browsing and reduce your traffic. See Understanding offline browsing for information on cache and offline browsing advantages.

To accommodate users' various browsing needs and preferences, Ad Annihilator provides four browsing modes. They are detailed in the following table:

Icon
Name	Download from Internet every visit to the page	Download from Internet or cache automatically	Download from cache if available	Download from cache only (offline mode)
Description	Every modified document and resource is always retrieved from Internet.	Only expired documents and resources are retrieved from Internet	Minimizes network traffic and retrieves documents and resources from Internet only if they are not already cached	Do not produce network traffic at all, take all documents and resources from cache. If they are missing form cache, do not retrieve them at all
Documents and resources taken from cache	Only those that have not been changed on the server since last download	Non-expired	All that can be found in cache	All
Documents and resources taken from Internet	All that have been changed since last download	Expired or without expiration information	Those missing from cache	None
Page loading time	Maximum	Medium	Low	Minimum
Network traffic	Maximum	Medium	Minimum	None
Recommen- dation for use	When you always need to get the most actual page version regardless of server expiration information.	When you always need to get the actual page version relying on server expiration information. Recommended for frequently updated sites browsing	When you want to minimize download time and traffic as much as possible. Recommended for rarely updated site browsing	When you want to produce no network traffic at all (switch to offline mode)
Advantages	You may rely on that the pages you see are the most actual page versions	You rely on the server to provide you with page expiration information. This mode is a good compromise between  necessity to have actual page versions and saving time and traffic	The download time and traffic is minimized. You may be sure that Internet requests are made only for those documents and resources that you do not have yet downloaded	You may be sure that no network traffic is produced at all
Drawbacks	Download time and traffic are maximum. The browser makes network requests even for non-expired documents and resources	If the server provided wrong or inaccurate  expiration information, the pages you get might be already expired	You may get expired documents and resources	You may get expired documents and resources. If a document or resource was not downloaded earlier, it will not be downloaded at all. This may lead to improperly shown or operating pages

See How to switch between browsing modes? to learn how to change browsing mode.

Server expiration information and browsing modes

In the preceding table we referred to server expiration information. Many web sites altogether with a document or a resource send a date until which it is valid. This date is called expiration date. It is assumed that after that date the document or resource becomes too old and that your browser should retrieve a new page from Internet if you try to open it after that date. If you navigate to that page before expiration date, the browser may choose not to download the page again but to retrieve it from the cache.

For example, if you opened a news site page at 9:00 AM, the site may send an expiration date after which this page is considered invalid, e.g., 10:00 AM. If you visit that page again between 9 AM and 10 AM, the browser may not download that page from the server but get it from the cache since the server told you that this page expires only at 10 AM. This expedites page loading and produces no network traffic. If you visit that page later after 10 AM, browser will have to download the page again.

The browser behaves itself as described above only in "Download from Internet or cache automatically" mode so this mode is recommended for browsing of frequently updated sites.

In "Download from cache if available" mode once the browser  has got a single page version, it will never retrieve that page from the Internet again but only from cache ignoring 10:00 AM expiration date. So, use this mode if you want to ignore expiration date and minimize page loading time and traffic.

In "Download from Internet every visit to the page" the browser will try to download a new page version even between 9 AM and 10 AM producing excess network traffic. Even here a traffic optimization is still employed - if the page was not changed on the server (there are ways to detect this), it is still not downloaded.

At last, in "Download from cache only (offline mode)" the browser will produce no network traffic at all. If a page was in cache, it will be shown. If not, the browser shows the message that the page is unavailable in offline mode. You should switch to another mode in order to see this page.