Jacksum is a free and cross platform data integrity software tool for computing and verifying checksums, CRCs and message digests (known as hash values and fingerprints). "Jacksum" is a synthetic word made of JAva and ChecKSUM. Jacksum supports 470 algorithms including national and international standards of cryptographic hash functions, candidates from round 2 and 3 from the NIST SHA-3 competition, and proposals from the 2005 NIST workshops before the SHA-3 competition, international accepted, modern strong cryptographic hash functions, eXtendable Output Functions (XOF) as cryptographic hash functions with a fixed length, and even broken cryptographic hash functions for education and backwards compatibility purposes, also checksums that can be found in software products and operating systems, and CRCs that are being used in many software products and protocols. Jacksum takes advantage of modern muliti-processor/multi-cores environments for parallel computation and verification of hashes. Jacksum supports the "Rocksoft (tm) Model CRC Algorithm", it can calculate customized CRCs, and it supports the combination of multiple algorithms. With Jacksum you can also find the algorithm used to calculate a checksum/CRC/hash or find files that match a given hash value. Both input and output are highly customizable, including charsets, encodings, formats, and compatibility files. Jacksum has opened it's source code and it is released under the terms of the GNU GPL. Jacksum is OSI Certified Open Source Software. OSI Certified is a certification mark of the Open Source Initiative. Jacksum is Free Software according the strong conditions of the Free Software Foundation. Jacksum has multiple interfaces. It can be used on the command line, it can be integrated into your preferred file browser, and Jacksum's API can be called by your own project if using it as a library.