For the last little while my toilet has been constantly been making a noise as you can hear in the video. I looked it up and it seems like there are two common causes of noise. It seems like the float and fill valve are working as intended. And I thought the flapper was okay since I applied pressure on top of it and it didn't affect the noise at all.
But I tried closing the intake valve for my toilet tank and the tank has been slowly draining. What is likely causing the leak? The water in the bowl seems still, not like there is a steady source of leaking into it? Any advice would be appreciated!
Edit: Thanks for the help everyone. The food colouring test helped show me that the water was leaking into the bowl. I wrongly assumed that since I applied pressure to the flapper to make sure it sealed that it was not the problem. But the flapper was the problem. Upon taking it out and inspecting it the whole thing was disintegrating and there were cracks allowing water through it.