Stack Exchange network consists of 176 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
postgresql feels more proper, but postgres has been more popular. They should be synonymized, though I don't know which one should be canonical.
The tags have now been synonymized, with postgresql as the master.
Upvote this if you prefer master postgresql ← synonym postgres.
Upvote this if you prefer master postgres ← synonym postgresql.