This is my deck, but this is not my cat...

The cat is very clean, though you're right.

might have been an adopted feral?

If OP wants to take it in, get it to a vet and scan for chips. (they may also a free check up/vaccinations.)

We think she belongs to the house behind us, so I'm gonna put a collar on her with a note tomorrow and see if we get confirmation.
- This is the way. We had what we suspected was a neighbor's cat that used to come visit. She didn't have a collar, so we bought one and attached a little metal keychain pill holder so we could pass notes to them. It was fun and we got to meet a new neighbor.
  
  Yeah I'm secretly hoping for a fun new game to emerge from this. Idk what the rules are yet, but I'm excited to find out.
  
  Somebody just invented the next hallmark movie plotline :)
  
  Though... it does sound like fun. make sure to encode secret messages into portions of the messages. "If you're reading this you must be very bored" or something.
  
  …and it will take place during Christmas time.
  
  "Hello! Why are you shitty and want your cat to destroy the local bird population and then (statistically) have their life cut short? Much love, Your Neighbor"
  
  EDIT: Downvote all you want but these facts are true:
  
  Cats decimate bird populations when they are loose.
  
  Indoor cats live longer, healthier lives.
  
  If you love your pets (obviously not talking about barn cats that technically have a job, but housecats), you'll do what's best for them.
  
  I doubt anyone here believes that what you stated is untrue. You're getting downvoted for being a passive-aggressive, melodramatic wet blanket.
  
  Is this you too?
  
  At a child's birthday party: "What awful parents, providing dessert. Don't they know childhood obesity and diabetes are on the rise?"
  
  At the pub: "Get your shit together, chronic alcohol consumption doubles your likelihood of stomach and liver cancer."
  
  With a friend: "Why do you hate yourself? You're clearly at least 20 pounds overweight. The earth has limited resources, stop using your advantage as a member of the global North and eating other people's food."
  
  They're all true and, like your comment, needlessly needling and hyperbolic. Consider there's more to communication than your false dichotomy defensive reaction of "true or not". There's also appropriate time, place, and tact, all of which you clearly didn't consider. That's why you're getting downvoted.
  
  We need a word that we can tag onto our posts that basically means "yes outdoor cats harm the environment and is bad for the cat, yes you should spay and neuter, yes I will register the stray with the county, check for a chip, and monitor lost posters to make sure the cat is not pre-owned before I adopt it, yes a cat is for life and I made this decision with sound mind, yes I know X food is not good for the cat, yes I know to get vaccines and regular cat care, etc etc etc". Or, perhaps people can just assume good will from other humans and not throw unsolicited advice their way every time they post a simple photo of a cat.
  
  But if you're on the Internet and not providing unsolicited, passive-aggressive advice, are you REALLY on the Internet?
- Make sure you get a breakaway collar or it could strangle the cat if it gets caught on something.
- Good luck on that. Make sure it's a break away one.
  
  It's actually a breakaway bowtie (for cats). What's the point in money if you can't spend it on the neighborhood strays 🤣
The cheaper (or often free) cat sterilization clinics near me clip ears instead of tattoo even if the animal is owned and indoor only.
- that sounds barbaric. I get clipping on ferrals, but if there's an owner.... why take the effort?
  
  I'm assuming it's because most people do not keep their cats indoors here. This is a very agricultural area. So quite a lot of cats are shop/barn cats. The cat I adopted in this state is actually tattooed, but I adopted him from a shelter a little over 200 miles away and things start becoming much more urban the further in that direction you go from my "city".
  
  I think (without any research, just from vague memory) the ear clipping isn't actually all that painful to the cat, and the benefits of an immediate visual identifier outweigh it. I wouldn't even know where to look for a cat tat.

There's no way that sparkling white cat is feral.

Feral when the ear was clipped at least.

My family also ended up with a clipped ear cat. She came up to us one night, and was friendly, then for the next two weeks she showed up everyday we got home from work. So, now she's our inside cat, and we all love her, she is so friendly to everyone. Even followed an AC tech around the house trying to get love from him too. One of the best cats I've ever had.

A couple of my ferals are friendly like this and I get them flea prevention when they climb in my lap.

You've never just taken a neat chomp out of a friendly cat's ear?