Glossary A–ZLetter C
Cache
A cache is a storage area in which a device keeps data it has already downloaded, so that it does not have to transfer it again next time.
On players, this mainly means media, schedules and templates.
The cache makes the player independent of a constant connection: images and videos play from local storage even if the network fails, and a video is downloaded only once even if it plays a thousand times. If a file changes, the player detects this, for example by its size, date or checksum, and downloads it again. Browsers and intermediate stations on the network have caches of their own as well.
Full storage prevents new downloads, so outdated files should be removed automatically. If a file is replaced under the same name, a cache may go on showing the old version; with web pages as content this is a common reason for displays that appear out of date. Clearing the cache solves some problems but triggers a complete new download, which on a mobile connection uses a corresponding amount of data.