I was following blender guru anvil modelling and encounter problem with triangles in face

Help! I was following blender guru anvil tutorial, and there’s a stage where blender guru can remove triangles on a face by just selecting four of it and press F.

but it didnt work for me in blender 2.8…

is the shortcut moved?

Watch the video. it’s a short clip from blender guru video and my attempt.

That’s because you haven’t split the face in the first place. When you select two vertices and press F you create a new edge only between the two vertices, it doesn’t cut the face into two triangles. To do that, you need to call the Vertex -> Connect Vertex Path operator. That one will split the face correctly, and afterwards filling with F will work. In your demo it looks as if the face is split simply because it’s flat. But if you, say, Subdivide that edge and move the extra vertex, you’ll see that the edge is just hanging in the air, not connected to any faces.

The edge that you’ve created in your demo you can delete by selecting it and doing delete -> Edges.

If you have created such edges (disconnected from faces) in your actual model, you can quickly find where they are by switching to edge mode and doing Select -> All by Trait -> Loose geometry.

EDIT: Also, don’t just do what Price does. Selecting faces by selecting vertices is very inefficient. When you need to select faces, switch to face selection mode and click on faces. Not only is it faster, it would also help you identify problems with geometry, for example in this case if you click a “triangle”, the whole quad will be selected, suggesting that that edge is loose.