Dogs can look so scary when they do this. My dad’s dogs would sometimes pull this face when they were playing, and I found it worrying at first, because I thought they weren’t really playing.

It was all chill though. Occasionally the older, more chill dog would do a growl and a similar version of this face, which would cause his boisterous brother to immediately back off (most of the time). That showed me that even if I couldn’t tell the difference between a play snarl and a real one (or at least, a warning one), it was perfectly intelligible to other dogs.