At the front or In the front? What is the difference?

At the front and in the front usually have the same meaning(in a forward position). There can be contexts where we use at(for shorter time periods, outside) and other contexts where we prefer in(longer time periods, inside).

In American English people say “I am sitting in front” when they have a position close to the action. In British English, people say: “I am sitting in the front”

At the front 

We use “at the front” to show our relative position to other positions. This is usually at an entrance point like a door or near the action.

Where are you? I am at the front door. 

“At” can be used for your position indoors or outside. The main point of the preposition ”at” is so that you can show your relative position. We use places like “the front door” to show where we are. The door is a reference point. 

In the front 

In the front is British English for events where you are close to the action.

I was sitting in the front. I could see everything.

“In the front” is also used for places that are inside like a car.

The steering wheel is in the front. 

At the front vs In the front

Notice that we often use the preposition ”at” for shorter periods of time to explain our location at the current time.

Where are you now? I am at the front of the seating area.

We use “in” for longer periods of time.

Where were you sitting for the show?

We were sitting in the front. (all night, British English)