Why are CDs circular?

Reason 1 : While working CD ,s has to rotate at high speed ,so in order to avoid vibration due to uninformed distribution of mass CD's are manufactured in circular shape . The best example what happens if CD 's are not in circular shape is vibration part of your mobile . read more

the cd/dvd drive rotates the cd/dvd and moves a sensor called the lens in and out to find a section of the cd/dvd called a sector that contains a block of information, actually the inside of a floppy disc is circular too, try breaking the case off of one. read more

They are circular so that they are more stable when spun around in the drive. Any other shape makes them wobble and shatter. read more