Java Edition version history/Development versions

Starting in the period between Beta 1.7.3 and Beta 1.8, Mojang publicly releases testing versions of the full update in order to get major feedback, especially for bug reporting, so that the official update is considerably more stable. While these versions were public, they were not auto-installed by the game and are completely optional.

Most of these updates follow the name-suit of "Pre-release" displayed on the version tags, although follow different naming patterns.

Automated Snapshots
Jeb tweeted that the format for the snapshots is yy"w"ww:tag:, which means the last 2 digits for the year, then the letter "w", then the week number, then an enumerating letter for that week.

Beta 1.9
Considered the "Lost Update", a full version under the name "Beta 1.9" never came. Instead, Mojang opted to delay the release of this update until MineCon 2011 and release it under the name "Minecraft 1.0.0". This decision was made after a few development versions tagged as Beta 1.9 were already sent out, so the name Beta 1.9 was kept for all of the development versions in the gap between Beta 1.8.1 and Minecraft 1.0.0, other than the Release Candidates.