Cats commonly purr when they are relaxed and enjoying attention.
But purring is not limited to happy situations.
How does a cat make the sound?
Purring comes from rapid activity around the voice box as the cat breathes.
The result is a low vibration that continues during both inhaling and exhaling.
Scientists have studied the exact mechanism for years, and some fine details are still being worked out.
Why do comfortable cats purr?
Purring appears in peaceful social situations.
Cats may purr while being petted, kneading, nursing kittens, or resting near a familiar person.
Kittens can purr when very young, so the behavior begins early as part of cat communication.
Why would a nervous or hurt cat purr?
Cats can also purr at the veterinarian, during illness, or when injured.
One possible role is self-soothing.
The important practical lesson is that purring by itself does not prove that a cat feels good.
Body posture, appetite, breathing, facial expression, and behavior all matter.
Can cats purr to get something?
Yes.
Some cats produce a more urgent version of purring when asking people for food or attention.
Behaviors that successfully produce a response can be strengthened over time.
How does purring fit with other cat signals?
A relaxed cat may combine purring with slow blinking, rubbing, kneading, and loose body posture.
A tense cat may purr while hiding or holding its body stiffly.
Context changes the meaning.
So a purr is useful information.
It just is not the whole conversation.
And that’s the short explanation.
Related explanations: Why do cats knead?, Why do cats slow blink?, and Why do cats rub against people?