Prime95, also distributed as the command-line utility mprime for FreeBSD and Linux, is a freeware application written by George Woltman.

For much of its history, it used the Lucas–Lehmer primality test, but the availability of Lucas–Lehmer assignments was deprecated in April 2021[7] to increase search throughput.

Trial division is implemented, but Prime95 is rarely used for that work in practice because it can be done much more efficiently using a GPU, due to the type of arithmetic involved.

[11] To maximize search throughput, most of Prime95 is written in hand-tuned assembly, which makes its system resource usage much greater than most other computer programs.

Additionally, due to the high precision requirements of primality testing, the program is very sensitive to computation errors and proactively reports them.