How are photos compressed?

Photo files are compressed using the JPEG compression standard. This is a format with losses or irreversible compression. The JPEG format makes it possible to achieve very high compression rates of around 60% to 80%, while maintaining good image quality.

The purpose of compressing images is to reduce the repetition of image data in order to be able to store the image without taking up too much space or to transmit it rapidly. Methods with compression loss are particularly suitable for normal images such as photos in applications where a minor loss of fidelity (sometimes imperceptible) is acceptable in order to achieve a substantial reduction in the data signalling rate.