Three different types of data can be recorded on CD. They all share the same physical block size (2352 bytes). However, they have different user block sizes (bytes effectively available to the user) depending on the level of error correction adopted: the lower the read accuracy required, the smaller the error correction code required, the bigger the user data block is. The following is a list of CD compatible data formats:

Audio

No extra error correction is required to read and play back audio. The user blocks size matches the "physical" block size and is 2352 bytes.

Mode 1/Form 1

Mode 1 and Mode 2/Form 1 formats are used to store digital data therefore the highest read accuracy is required. The user block size is 2048 bytes (2KB). The remaining bytes are used to store sync patterns, block headers and error correction and detection codes (ECC/EDC).

Mode 2/Form 2

This format is used almost exclusively to store digital video data, thus requiring only moderate read accuracy. The user blocks size is 2324 bytes. The remaining bytes are used to store sync patterns, block headers and error detection codes (EDC).