After flushing, the bowl on the toilet fills too high, nearly to the top before the tank does. I do not know what to try first.
You have a partial drain blockage, probably in the S shaped toilet trap.
Wait. The things that go down toilets should disintegrate quickly in water. Sometimes they disintegrate slowly. People who are highly constipated or who use facial tissues instead of toilet paper can cause this. Sometimes waiting solves the problem. Other things don't disintegrate at all ... rags, sponges, tampons, etc ... then go on to #2.
Try a *good *plunger.
- Try a toilet snake
- If those don't work, you have to remove the toilet from the floor an examine the trap. Look on youtube how to remove and replace a toilet or call a plumber if you're not comfortable with it, or if it is your only toilet.
Muriatic acid is a choice if a plunger doesn't work. I am not a fan of the toilet snake because sometimes it pushes the clog worse, and if you use enough force you can crack things and find out later.
Muriatic acid is some serious stuff. You need to be wearing gloves and eyewear and a mask but it is easy and quick. If the toilet is "full" you can just pour a cup of the acid directly in the toilet - don't splash it. As the water settles, flush. If it still won't go down keep adding a cup each time. Never had a toilet go past 3 tries and most in 1. Also the acid will make cleaning the toilet easier.