Development stage

alpha version or alpha release is the first release of a computer program or other product, likely to be very unstable but useful for demonstrating internally and to select customers. It is also called "preview or technical preview.

A beta version is not fully debugged or fully functional but satisfies a majority of the requirements. Beta versions (or just betas) are an intermediate step of the full development cycle. They are released to a group of beta testers (or, sometimes, to the general public) for a user test. The testers report any bugs that they found, features they would like to see in the final version, etc. When a beta is released to the general public it often becomes used almost as widely as the finished product is (when the product is completed.) Usually freeware or open-source betas are released to the general public while proprietary betas are released to a relatively small group of testers. Recipients of highly proprietary betas may be under a non-disclosure agreement.

The term beta is used to differentiate the version from an alpha release, made at an earlier stage in development.

Release candidate is a final product that can be released unless fatal bugs are detected. In this stage, all functionalities are done and all showstopper class bugs fixed. The term is mostly used by Microsoft.

In opensource programs, version numbers and distinction stable and unstable are more commonly used. Particularly in Linux operating system, even numbers in minor version indicates stable and odd numbers indicates unstable version.