Blu-ray disc, computer artwork. Blu-ray discs work on a similar principle to CDs and DVDs. They store data by reflecting laser light onto a receiver. Unlike these earlier formats though, they use blue laser light, which has a shorter wavelength, enabling data to be stored more effectively. This, together with other innovations, allows a single layer disc to store 25 gigabytes of data. A conventional compact disc stores less than a gigabyte.