These things never worked for me. Maybe I don't understand how to look at them correctly to get whatever 3D effect they're supposed to make, but for the life of me, I could never see anything at all in those patterns, neither on screen nor when printed.
edit: I found this video[1] with pairs of images that tells you to hold sunglasses in front of your right eye if you can't defocus your vision correctly. This worked for me with an ND filter, it really feels like it shouldn't do anything but I did see depth. Those patterns though, still no idea how to make them work.
It lists multiple methods along with an "easy" stereogram to view. Maybe one of them works for you, it worked for me.
edit: I don't see it mentioned on the page, but in my experience the absolute size of the image matters. It works better on a computer monitor for me rather than a smartphone screen. Play with zoom levels.
TBF, these "hidden" autostereograms are the most challenging to "see" - it's probably better to start off with two "actual" pictures printed or displayed side by side (because there you have some cues to how far you are from the images overlapping), and then try to apply the same technique to autostereograms? I can manage to do it most of the time, but it always takes some effort. I think it also helps if the image is bigger, but YMMV...
Same for me, I can't see anything in those images. I have astigmatism and red/green colorblindness though (which I discovered later in life). Could be related?
I have astigmatism as well and it initially took me a very long time to manage to see them, it might be that it has an effect
(I practiced enough that I then learned to see them at a blink of an eye, and it helped my normal vision a lot btw)
I used to have really bad myopia, but right now, many years after laser surgery, I still have nearly perfect vision. I feel like my main problem is that I can't overcome my reflexes.
A technique I've seen is that you put a reflective transparent surface in front of the autostereogram and gaze at your own reflection. This puts your eyes at the right focal point.
I've been pretty good at seeing these in the past, but I had no luck with the images in the article.
edit: I found this video[1] with pairs of images that tells you to hold sunglasses in front of your right eye if you can't defocus your vision correctly. This worked for me with an ND filter, it really feels like it shouldn't do anything but I did see depth. Those patterns though, still no idea how to make them work.
[1] https://www.youtube.com/watch?v=mLsODo7ycaA