What Is Lossless Compression?
- Compressed files must be "decompressed" and returned to their original format in order for most programs to use them. Lossless compression is used most often when the reassembled file must be exactly the same as the original. This is important for executable files and others that include source code. There are also lossless audio formats that do not delete any of the original audio information during compression. Lossless audio formats offer the potential for the highest quality sound output.
- Lossy compression is also used to reduce the amount of space a file consumes. These algorithms may produce a reassembled file different from the original, uncompressed file. For example, the MP3 audio format deletes relatively quiet, background sounds that are less noticeable. This compression method produces a file that requires much less space and a similar sounding audio file.
- The main advantage of lossless compression formats is exactly what their name implies; no information is lost and hard drive space is saved. There are also a variety of open source or free lossless compression formats such as .ZIP and FLAC. Unlike with a lossy format, compressing a file with a lossless format will never render that file unopenable.
- Lossless formats can rarely match the amount that a lossy format can compress a file. By deleting some information, lossy formats can more effectively reduce a file's size. Any compressed file, whether saved in a lossless or lossy format, will take more time to open because it will have to be reassembled.