A lot of people still struggle with double jumps, so I made this guide to help people become more consistent with double jumps.

To do a double jump, you must be on the ground, press the jump button for exactly 1 frame (1/30th of a second), wait for 2-7 frames (5-7 in volume 3), and press jump again. The main reason double jumps fail is that the player pressed the jump button for more than 1 frame. Thus, for better double jump consistency, you'll want to focus on making the jump button taps last as short as possible while still having the game detect them. If you can master this, your double jumps will become consistent.

Now, a lot of people may not be able to press the jump button for only 1 frame in a consistent manner, possibly due to their keyboard. Thankfully, there is an alternative strategy that does not rely on 1-frame taps yet can also give you consistent double jumps. What you do is you press the jump button and the pause button (p) at the same time. If you did this right, you will hear the jump sound, but red ball will still be on the ground. Then, while making sure you aren't holding the jump button, unpause the game. After the unpause, wait a few frames and press jump. If you did this right, you will double jump. If you have a numpad that is next to the enter key, you can more consistently jump and pause at the same time by pressing p and numpad 8 with the same hand while having num lock disabled. When done fast and while holding right, the inputs look like this:

pause + jump -> no input other than right -> unpause -> no input other than right -> jump

The main disadvantage of this method is that it loses time: over the course of the run, if you do this strategy on every double jump, and you unpause as soon as you can after pausing, you will lose a few seconds from the frames the game is paused. However, if your double jump consistency is garbage with the other method, you'll probably save more than a few seconds from hitting most if not all the double jumps in the run. I personally find this pause buffer strategy to be a lot easier to perform consistently than the tapping strategy, so if I did a run with this strategy, it would save time over doing a run with the tapping strategy because of being able to nail double jumps more often.

I hope this guide helps you increase your double jump consistency, and I wish you good luck on your runs!