Online hash generators are tools that allow you to create a "hash" from a piece of input data. A hash is a fixed-length string of characters that is generated from an input, such as a file or message, using a mathematical algorithm. The hash is unique to the input data, so any change in the input data will result in a different hash. This property makes hashes useful for various purposes such as verifying the integrity of data or storing passwords securely. Some popular online hash generators support various algorithms, such as MD5, SHA-1, SHA-256, etc.