If you did it on the internet, then it wasn’t an IQ test. IQ testing is an academic dicipline that is performed in a controlled environment with a suite of different tests over the course of several months, preferably years. When done properly in this way then they are very accurate measures of intelligence.
They must be accurate as I scored very low marks when I was 11. Got me sent to a tough secondary modern school for a couple of years which made me vewy vewy fwightened!