Can you get a feral cat’s trust without taking her in?
Can you get a feral cat’s trust without taking her or him in? I don’t actually think that it matters whether you take him in or interact with him outside. Theoretically it is easier to socialize a feral cat in your home because it’s more comfortable and you won’t have to contend with weather conditions and other disturbing elements. And it will take a long time so being comfortable during the process is quite important. However, you’d be unlikely get him inside the home until he trusts you so it’s a catch 22 situation.

Normally outside
However, the process of socializing a feral cat can take place outside and nearly always does. There are situations where the home owner has covered outside space suitable for a feral cat home which is a nice way to proceed. I have read the statements and stories of many feral cat caretakers, normally involved in TNR programs, who have formed close relationships with feral cats. These cats clearly trust the person caring for them and they love their feral cats in return. When an individual feral cat shows their trust in their caretaker, it is a magic moment and quite emotional.
Trust and socialisation
Trust does not necessarily directly equate with the cat being fully socialised or domesticated. But socialisation is part of the trust-making process. Also a lot of feral cats are not totally feral by which I mean they are semi-feral and therefore accustomed to having people around.
Then there are stray cats as well which are wondering domestic cats which may distrust people but it will be easier to gain their trust. I remember stories from women who have spent months and months gaining the trust of a feral cat. They have succeeded by taking very small incremental steps through feeding the cat and then perhaps gently playing with the cat and finally touching him or her.
Cat prefers to stay outside
Sometimes the story ends with the cat happily ensconced in the woman’s home, getting on nicely with the resident cat. Sometimes it won’t end that way. The feral cat will learn to trust the person but prefer to stay outside, in which case the best course of action is to build an outside home for the cat and learn to interact with the cat on their territory.
Yes
The answer to the question is, yes, you can gain the trust of a feral cat without taking him in. All you need is lots of patience, slowness, gentleness, commonsense, time, energy, a loving attitude, excellent food and a bit of play because playing with your cat is the greatest way to get him used to you.