Loose, bouncy body language usually means playing
Stiff, tense bodies usually mean fighting
Relaxed ears and normal whiskers usually mean playing
Flattened ears and puffed-up fur usually mean fighting
Play often includes taking turns chasing or wrestling
Fighting often includes one cat pinning, cornering, or relentlessly pursuing the other
Play bites are usually gentle and controlled
Fighting bites are usually hard and repeated
Play often includes pauses and breaks
Fighting usually has little or no pause
Silent or occasional chirps, trills, or soft vocalizing usually mean playing
Hissing, growling, yowling, or screeching usually mean fighting
Claws often stay mostly sheathed during play
Claws are more likely to be out during fighting
Cats that separate and re-engage calmly are usually playing
Cats that cannot disengage or keep escalating are likely fighting
Mutual role-switching usually indicates play
One-sided aggression usually indicates fighting
A relaxed tail or gently swishing tail usually suggests play
A puffed-up, thrashing, or lashing tail usually suggests fighting
If one cat is trying to escape and the other keeps attacking, it is likely fighting
If both cats seem engaged and neither looks distressed, it is more likely play