Why files are compressed

Compression makes a file smaller, and every benefit of it comes from the same thing: the file is stored and sent using fewer bits. That helps in three practical ways.

More files fit on a device

A compressed file takes up less storage space. That matters on any device with a fixed amount of storage, such as a tablet, a memory card or a school's network drive. If each file is smaller, the same amount of space holds more of them, so you can keep more work before you have to delete anything or buy extra storage.

Files are quicker to send and receive

A network can only move a certain amount of data each second, so fewer bits means less waiting, and smaller files transfer faster — both uploads and downloads finish sooner. The robotics club films a 90 MB video of its robot completing a course and uploads it to a shared folder. Compressed it might be 18 MB, so only about a fifth of the data has to travel, and the upload finishes much sooner.

Less bandwidth is used

Bandwidth is the amount of data a connection can carry in a given time. A smaller file takes less of that capacity, so while it is being sent other people on the same connection can still load pages and send their own files without everything slowing to a crawl.