Images and graphics used on the web are often compressed to make them easier to work with and transfer. File formats that can be compressed and later decompressed without the loss of any data are referred to as lossless. File formats that achieve compression by deleting data are referred to as lossy. PNGs are lossless, meaning that they can be compressed without the loss of any data. JPEGs, another common file format used for pictures on the web, require less disk space, but are lossy and image quality is reduced when images are compressed.