Here are some methods to determine if a cat is a mixed-breed cat:

Check the weight: Domestic cats generally weigh 6 to 16 pounds (larger domestic cats may weigh more).
Look at their physical condition: Stray cats are naturally adaptable and have good physical condition, so they rarely get sick.
Look at the characteristics: Generally, domestic cats have short, round heads, round paws, and medium-sized tails.
Consider their personality: Most domestic cats are free-range, independent, and not overly dependent on their owners.
Consider the price: mixed-breed cats are cheaper than other purebred cats.