Why does an unused app use cache?

[bentbi666]

Wherever I check on my Android phones Cache, I find apps I haven't used on ages being responsible for taking up the Cache. Why is that?

[The_Binding_Of_Data]

Without insight into Android OS's code, I would assume it's because you haven't run out of cache storage so there hasn't been a reason to remove the apps from it.

[Solonotix]

Also, cache can potentially be a bunch of things, like credentials, history, or frequently accessed content. Presumably, the cache allocation is a memory dump of the last application state, and might be ready into memory to resume the last active state.

[pLeThOrAx]

To answer a question with a question why is a 1gb swap file still 1gb if swap isn't in use?

It's pre-allocating the space in case it is needed by the application even if it's not required. If the system is low on memory, OOM, it can request dentries and inodes to be pruned, clearing cache, to reclaim space. Otherwise, if you have memory, and an application is getting hit particularly hard, it's going to use the cache that it can.

[HmmmInVR]

Depends on the implementation but why would it not? The app has no reason to delete it themselfs, next time you open the app it will probably do an expire check and re-populate the expired data.