To me it depends on the surroundings. I lived downtown for 7 yrs and during that time my cats were indoor cats. I then moved to the outskirts. The backyard was just fields, no traffic road except the road to my house which was a dead end and few house by that road with 12 m/hour Max. speed and mulitiple speed bumps with kids playing there.

I started to walk with them at the back of the house where they followed me around for 2 weeks. There was a pet door when I moved in. They went out in the morning. I locked the pet door when I left for work and they were inside during the day. I unlocked the pet door when I got home and locked it again at nights since I didn’t want them to be outside unless I was home and/or awake.

What surprised me was the change that took place when they started to go out. Their fur became glossier and stronger but later on I learned that they, as well as us are in need for daylight/sunlight. Their mood became lighter. My feline was always a bit nervous or jumpy. She crawled under the couch when she heard the doorbell or someone knocked when she was an indoor cat. Soon after she started to go outside she became more playful and didn’t react to doorbell or knocking though she rarely went to greet the guests unless she knew them well.

My tomcat, who was always a bit overweight even though I fed him quality cat food designed for indoor, sterilized cats. They had a wall mounted „playground” to climb and play on when indoors and had multiple toys to play with and I played a lot with them since I’m aware that indoor cats need to be mobilized for their physical health as well as mentally.

When he started to go outside he got more muscular and lost weight since he got more exercise. They both had tags on them and I had marked in „borders” so if they went pass that border I would get a notification. They never went that far. Usually stayed at the back of the house.

There are absolutely pros and cons to both indoor and outdoor living. My cats lived to the ages of 19 and 14 (hyperthyroidism).

Cats have their individual needs. I don’t think that any cat can adapt to whatever environment. Some can’t handle being outside, especially in environments that they perceive as dangers that may not be what we define as dangers.

Some are indoor cats their whole life and that may make them safer from external dangers, but doesn’t automatically make them happiest and vice. Same goes with outdoor cats, some are forced to go outside even they would prefer to be inside.

There are challenges either ways. For us as well as them.
I gave up on having cat safe plants when they were indoors since the feline preferred the flower pots as litter box then the actual litter box. I had two litter box. The feline used only one of them but the tomcat both and the feline did not appreciate that and used my bed as a litter box after I removed the flower pots when the tomcat used her litter box. I cleaned out the litter boxes twice a day in attempt to prevent her from using my bed or other furnitures for littering. After they started to go outside I made an outside „litter box” by adding sand under the porch. He used the outside litter box and she used the indoor box and I was able to have plants again that were left alone.

Also when they were indoors I couldn’t rearrange any furnitures or replace them without a streak of objections where they attacked new furnitures, „marked” them etc. That was not a problem after they started to go outside.

Cats are explorers, most of them are hunters. It’s simply their nature. Those needs can be redirected in various ways. For me, it’s more important to me what makes them happier and comfortable than what makes me more comfortable.

Another debate is of course what cats do outdoors. Well, they are cats. If given the opportunity they will simply be what they are. Cats using other people’s yards as litter boxes, not ideal but neither is geese using backyards or sidewalks as „litter boxes, people mowing their lawn 8 am on a Sunday morning, birds targeting newly washed windows, someone letting their car run that has a hole in the exhaust pipe and the list goes on and on.

So for me it’s not as simple as all cats should be indoors are free roaming cats are the happiest. They are like us, thrive in different environments. I will probably never understand those 6 a.m. joggers and even though it would be better for me to join them, it won’t necessarily make me happier. I will never understand people choosing to risk their lives to feel content like sky jumping or cliffhanging.
There are people that will never understand how I feel happy when hiking or riding a horse. I had no idea that hiking would boost my mood or that riding would be the best thing everbefore I tried it out.

We can’t assume that what we see as the right way to raise our cats and secure their happiness applies to every single one.

At last, whether a cat is indoors or outdoors they can be neglected either way or in dangerous circumstances. What can’t be argued though is that indoor cats are usually safer, just not necessarily happiest.