The login message prompts the user for a username and password and attempts to login to the current serverside host. The tiddler $:/status/IsLoggedIn reflects the current login status with the values "yes" or "no", and $:/status/UserName reflects the current username.

The login message is handled by the TiddlyWiki core SyncMechanism which invokes the current SyncAdaptorModule (typically the tiddlywiki/tiddlywebadaptor plugin).

Introduced in v5.1.23 The login message can optionally accept parameters called username and password that immediately attempts to login with the specified credentials without displaying the prompt