Caching is performed by every browser and every operating system to speed up operations and reduce bandwidth.

Browser performance is the name of the game with programmers who write browsing software. The know that consumers rate performance on how fast a page loads. Employing caching greatly improves performance because it is much faster to get a cached DNS response than it is to go out and look it up again. It only saves a few milliseconds, but those milliseconds add up quickly. If the browser is getting an address from a local cache, the CSB won't see it or act on it. This can be frustrating when trying to block or unblock web elements, because it does not appear to be working.

To add to the mix, there are multiple places where caching occurs.

• Your browser
• Your device DNS service
• The CYBERsitter BLACK itself
• Your Upstream DNS provider
• Your ISP

We humbly recommend that you practice patience in these situations. We experience the same issues ourselves. In the case where you want to speed things up, below are some procedures you might want to try.

Your CSB is affected by 2 types of caching.

DNS Caching is performed by your computer or other client device, sometimes by your router, by your ISP and by the upstream DNS provider.

A typical problem with DNS caching when using a CSB might be when you whitelist or blacklist an address. Your computer or other device might be caching the original address, and feeding you the original address when you try to access a newly blocked or allowed address.

Usually it is easier to just wait it out. The cache will eventually expire and your changes will take affect. You can usually hurry this up by manually clearing your computers cache.

• Open a DOS (Command) window.
• Type ipconfig /flushdns and hit Enter
• Close the DOS window

Yosemite 10.10.4 or newer

• Make sure you are logged in as administrator.
• Open a Terminal window.
• Type sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder and hit <enter>
• It will ask for your sudo credentials (your regular login password)
• Enter your password and hit <enter>
• Close the Terminal window

Many Linux distributions do not use DNS caching at the operating system level. Instead, applications (such as web browsers) maintain their own internal caches. To clear an application's DNS cache, often all you need to do is restart the application.

If your Linux computer does use a DNS caching service, however, consult its documentation for instructions about how to clear the cache

1. Start Google Chrome.
2. In the address bar, type chrome://net-internals/#dns. Google Chrome displays a list of hosts in its internal DNS cache.
3. Click Clear host cache.
4. In the address bar, type chrome://net-internals/#sockets.
5. Click Close idle sockets, and then click Flush socket pools.

Most browsers generally support holding down the <shift> key and clicking on the button. This doesn't seem to work consistently however. Some browsers, under certain conditions, will load a page that is several days old.

There are several other procedures however, so if you want to learn about all the types of cache clearing, there is a good article here:

https://kinsta.com/knowledgebase/how-to-clear-browser-cache/

There is one more type of caching, but it does not affect your CSB operation much. It is called “pre-fetch”. Pre-fetching resolves every URL it finds on the active page even before you click on them. You may never click on them at all, but if you do, the DNS lookup has already been done so the requested page loads more quickly. Again, this gives the user the perception that the browser is faster than it really is.