The most frequent distinction seems to be that a "Tasse" has a handle, but it's also common to take the form or material into account. https://www.printplanet.de/wissenswertes/rund-um-produkte/die-unterschiede-zwischen-tassen-und-bechern https://www.pinkcube.de/becher-oder-tasse https://de.wiktionary.org/wiki/Diskussion:Tasse

Danke!

Der Becher hat im Vergleich zu einer Tasse eine höhere Form und meistens keinen Henkel.

Probably a question of definition, but to me a Tasse has a handle (mug), a Becher doesn't (cup).

They do look the same in Google's images