The two dogs here are a beagle (white and “lemon” on leash and wearing the harness) and a longhaired dachshund (from the coat length I am betting an older puppy, still under a year).
First thing I look at are the tails (red arrows). Specifically the base of the tail right where it attaches to the body. The beagle’s tail is raised straight up with the base of the tail almost vertical. The dachshund’s base of tail is level with his back. Yes the tip is up but never mind the tip, the base is low. The tip is off center so the tail is not tense or still.
That alone makes me relax. There will be no fight here.
If both tails were up, stiff and motionless at the base then something is much more likely to happen. But when one is up and the other down and the one up is disinterested? All is usually well.
What else am I reading? Well, next I notice the beagle’s head position. It is low and looking away from the dachshund. Her ears are completely flat which means relaxed. When floppy-eared dogs are tense, the ears develop folds.
My guess? This is an older dog who is playing a game I call, “Dog? What dog?“. This is a game older, sensible dogs play with young, slightly rude pups.
If that high, stiff tail was matched with a high head, tense ears and if that head was in alignment with the spine and tail, I’d be on alert. But it isn’t so I’m not.
The dachshund is giving a typical dog sniff, head low, spine slightly curved, tail relaxed, ears soft and hanging. He means no harm.
So, by reading dogs carefully, you can make a good bet on what is safe and what is unsafe. These two? Totally safe.
Now you know.