BridgeDB implements four mechanisms to distribute bridges: HTTPS, Moat, Email, and Reserved.
Bridge operators can check which mechanism their bridge is using, on the Relay Search.
Enter the bridge's
<HASHED FINGERPRINT> in the form and click "Search".
Operators can also choose which distribution method their bridge uses.
To change the method, modify the
BridgeDistribution setting in the torrc file to one of these: https, moat, email, none, any.
Read more on the Bridges post-install guide.