What does clear cache mean on apps


Android Question

When you clear cache on apps like facebook and such what does it do exactly
Hello and welcome to Android Forums! :)

Here's quite a detailed explanation from one of our members:

Manually clearing cache on Android generally accomplishes two things:

1.) One you've already discovered -- i.e., it provides a more intimate familiarity with various apps, which is not really a great value, as you have likely concluded.

2.) It slows your system and applications down. The whole purpose of cache is to improve performance by reducing the frequency of redundant data movement and processing.

Android recovers cache only on an as needed basis, and so more often permits intended performance gains to be realized. When you manually delete cache, this somewhat arbitrary activity does little more than slow your apps and device down, which is opposite of what many users expect it to do. Clearing cache is equivalent to filling your swimming pool every time before you jump in, and then immediately draining it every time you get out. All of that effort used filling and draining the pool wastes valuable time and energy that could instead be used for swimming. When you clear cache, the CPU, network, etc. has to do all of that work over again, merely wasting energy to accomplish the same end result. Android and applications typically know better than users when cached data becomes stale or dirty, and unless there is some defect in the software, cache does not typically require any manual action.

Performance analysis for just about any computer system should start with an assessment of CPU usage, not memory usage. You typically only move onto memory if you determine that CPU resources are not an application bottleneck, and that there is some other resource impairing performance. You should always check CPU usage first though.

I use a very handy app named Watchdog. It monitors CPU usage of background apps and alerts when a threshold is exceeded (40% by default). This is more likely where you are going to find causes of problems on Android systems. Apps that use too much CPU in the background make the system feel generally slow and less responsive. You actually want your foreground apps to use as much CPU as they can get so you experience fast, crisp response times. That's why using a tool that monitors and alerts on excess background CPU usage is important to assess percieved performance problems. This concept is not at all unique to Android. This is true of any system capable of running multiple concurrent processes.

If you monitor your background CPU for a few days, you may be surprised at what you find you are able to clean up. I use this method to evaluate any new app that I install. If the app fails the performance assessment test, I either figure out how to work around the problem (like always exiting Dolphin), or I delete the defective app from my system.

I keep Watchdog installed and monitoring all of the time. It uses a very trivial amount of system resources and I never see system slowdowns without being alerted to the cause.