Cats are quiet talkers. They save most of their messages for the tail, ears, eyes, whiskers and the way they hold themselves. The trick is to read these signals together, never one at a time: a tail that is up while the ears are flat and the pupils are huge is not a happy cat.
Pick what you can see on your cat right now. The card will tell you the most likely mood and what to do about it.
Choose at least two signs
Pick what you see above and your cat's likely mood will show up here.
A tail held up is a friendly greeting. A tail tucked between the back legs points to fear or anxiety. A tail held out and slowly swishing can mean frustration, and a puffed-up tail with an arched back and sideways stance is a clear "stay away".
Relaxed cats keep their ears facing forward. Ears flat against the head usually mean fear, and ears turned sideways or back show a cat who is unhappy or on edge.
Half-closed eyes and slow blinks are a calm, friendly message, and a comfortable cat may blink back if you blink slowly at them. Wide pupils and a fixed stare can mean stress, though pupils also grow in dim light, so look at the rest of the cat. Staring at your cat can feel like a threat to them, so soften your gaze. Relaxed whiskers sit out to the sides. Whiskers pushed forward mean high alert, and whiskers pressed against the face mean fear.
Cats that feel safe lie or curl up loosely. A scared cat keeps low, pulls its head in and plants all four paws, ready to run. Purring is often a sign of contentment, but cats can also purr when stressed or in pain, so check the body too. Hissing, growling and spitting are warnings: back off.
Read the whole cat, not one signal, and when the signals say "not sure", give space.
Sources: Cats Protection: Cat body language, International Cat Care: Cat communication and Petplan: Understanding cat body language. Read the full pages for more detail; the welfare groups describe some signals slightly differently, and none of this replaces a vet's advice.