Snapshot builds of versions under development are normally done daily. They represent the latest state of the sources for each respective version. You can find them at the following locations:
| Platform | Versions | |||
| All | Firebird 6.0 | Firebird 5.0 | ||
| Windows | Firebird 4.0 | Firebird 3.0 | ||
| Linux | Firebird 4.0 | Firebird 3.0 | ||
web.firebirdsql.org/downloads/snapshot_builds/
Alternatively, you may find recent snapshot builds at Appveyor:
Go to https://ci.appveyor.com/project/FirebirdSQL/firebird/history
Find and click the tag you are interested in