Make your observations, note what each body part of each dog is doing.
Grey & white Italian greyhound-
Face: ears back but flopping with motion, eyebrows and forehead smooth, mouth is out of view but top of muzzle appears smooth
Head: lowered, turned to the side and facing the other dog
Body: shoulders lowered, in motion, paws lifted and front paws slightly apart
Tail: loosely raised, tip curling to the side
White unidentified fluffy dog-
Face: ears semi rotated back and raised higher on skull, eyes wide and rounded, mouth is tense with pursed lips (corners pushed forward) and a ridge visible along jawline
Head: raised, oriented towards other dog
Body: weight shifted back from front feet, body tilted and in motion, front legs apart, back legs off ground
Tail: loosely raised, swaying with movement
Review the above body parts and compare with the photo to spot these cues yourself before reading further!
This photo was taken at the dog park. The dogs didn't know each other but had been interacting for some time.
These dogs are playing! The Italian greyhound shows clear prosocial playful body language. While the white dog's body language is more conflicted, with a loose moving body but tense face, these signs are mild and well within what we can expect to see during play. Momentary flashes of surprise, apprehension or defensiveness are okay as long as play overall remains healthy and two sided. Consider these flashes data points, which you can track over time. Are the dogs displaying these signs with prolonged duration or dozens of times within just a couple minutes? Or just here and there as they take in the fast paced game? Think about how many small expressions we may make while playing games ourselves!