Why does my cat purr?

Most people think purring = happy cat. It's more nuanced than that. Purring is a self-soothing mechanism. Cats purr when they're content, but also when they're stressed, in pain, or even nursing kittens.

The vibration (around 25–150 Hz) appears to have actual physical benefits — multiple studies have shown frequencies in this range promote bone density and tissue regeneration. Some researchers think purring is partly a healing mechanism, which would explain why cats purr through illness and injury.

How to tell which kind of purr:
- Content purr: relaxed body, slow blinks, soft kneading, paired with rolling or settling in
- Stressed purr: ears back, dilated pupils, tail flicking, often happens at the vet
- Hungry/demanding purr: higher-pitched, rhythmic, often at 6 a.m. — researchers call this the "solicitation purr" and it's evolutionarily designed to be impossible to ignore

Kittens learn to purr within days of birth — it's how they communicate with mum (who can't see them well in the early days but can feel the vibration).

So: a purring cat usually feels safe, but the rest of their body language tells you which kind of safe.