Jacksum is a free and cross-platform data integrity software
for working with checksums, CRCs, and message digests (hashes).
Jacksum supports 477 algorithms, including the most common cryptographic and non-cryptographic hash functions. Jacksum also supports the "Rocksoft (tm) Model CRC Algorithm" to describe CRCs, so additional 1.0399*10^267 customized CRCs can be used.
Jacksum can recursively compute hashes with multiple algorithms simultaneously. Jacksum takes advantage of modern multi-processor/multi-core environments, and saves time by hashing multiple files in parallel.
Jacksum can perform a verification of hashes against a set of known hashes, and it can detect matching, non-matching, missing, and new files.
Output can occur in predefined standard formats (BSD-, GNU/Linux-, or Solaris style, SFV or FCIV) or in a user-defined format which is highly customizable, including many encodings for representing hash values, including binary, decimal, octal, hexadecimal with lowercase or uppercase letters, Base16, Base32 with and without padding, Base32hex with and without padding, Base64 with and without padding, Base64url with and without padding, BubbleBabble, and z-base-32.
Input data can come from files, standard input stream (stdin), or provided directly by command line arguments.
Jacksum supports many charsets for reading and writing files properly, and it comes with full support for all common Unicode aware charsets such as UTF-8, UTF-16, UTF-16BE, UTF-16LE, UTF-32, UTF-32BE, UTF-32LE, GB18030, etc.
With Jacksum you can also find the algorithm used to calculate a checksum, CRC, hash or find files that match a given hash value.
Jacksum provides many interfaces actually. Jacksum is a command line tool, and it can be integrated in your file browser. Jacksum can also be used as a runtime library in your own projects by using its API. Jacksum keeps the binary small, because it bundles only what it really needs to do the job.
Jacksum has opened it's source code and it is released under the terms of the GNU GPL 3 or later. 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 is a synthetic word made of JAva and ChecKSUM, because Jacksum is written entirely in the Java programming language. Therefore the software runs cross platform, e. g. on any platform having a Java Runtime Environment including GNU/Linux, Microsoft Windows and macOS. without recompilation.
With Jacksum you can check if a filetransfer was successful. If you download software or large files, like .iso-files from the internet, often there is a checksum or a hash value provided. With Jacksum you can calculate such a checksum or hash from your local copy. If both check sequences are identical you know that the file transfer was successful.
You can find all files that matches or not matches a set of known hashes. In other words, you can find files by their fingerprints and you can find all duplicates of a file. This is useful, for example, if you need to identify any libraries on your servers that have a known security vulnerability.
Since Jacksum reads each byte of a file, you can check what files are still fully readable on your media.
Since Jacksum supports recursiv file processing, you can compare two directory trees. Therefore you will be able to verify, if your copies or backups are identical with the original source, even if you don't have access to both trees at the same time (compare two DVDs with just one drive for example).
Since Jacksum supports platform independent and compatible file formats, it helps you to verify data integrity of burned data on DVDs even after many years and even if you will have changed your Operating System.
Jacksum can support you by the unidirectional filesynchonisation, even if you don't have a connection between the two computers.
Jacksum can help you to create incremental backups.
If you are a developer, Jacksum can help you to create patches for your customers.
You can use Jacksum for intrusion detection, because Jacksum can check whether and what files have been modified, deleted or newly created on your system. Jacksum can not only check the content of each file you want, but also the timestamps of each file.For more information please read the FAQ section.