You need to clean it yourself. If you just don't have enough memory and the memory you need is not too big, then there may be the possibility that the phone will automatically clean up the memory during the download process. My 6s, 16g is always like this.

In addition, if manual cleaning is needed, some software can find the settings and clean the cache. For example, today's headlines, WeChat, etc. There will be a storage place. Just set up and clean up the cache.

More importantly, you can uninstall the software and download it again, which can clear the memory in a short time. Recorded a lot of data, such as head portrait, other people's head portrait information can be directly seen, because you formed a cache. This method can be used to treat the symptoms, not the root cause. It is estimated that it will be full after a long time.