Basic Local Alignment Search Tool (BLAST) is a popular sequence similarity search tool. The National Center for Biotechnology Information (NCBI) maintains a public BLAST server at The NCBI BLAST server is intended mainly for interactive use, with the expectation that users will perform a moderate number of searches (i.e., 10-20) per day.

Some users have many more searches to perform than can be accommodated at the NCBI site. For such batch users, the NCBI offers the stand-alone BLAST+ package that can be run on local hardware. Running the stand-alone package requires that the user have access to sufficient compute resources (e.g., a local cluster) as well as some degree of familiarity with IT issues and command-line applications.

Additionally, some users do not need to perform a large number of searches on a regular basis, but may need to do so occasionally. Some users have proprietary sequence data to search and cannot use the NCBI BLAST web site. A cloud provider may offer an acceptable solution for these scenarios.