I have the same problem, and it turns out it is being caused by Firefox. This seems unlikely, so I'll lay out the facts below.
At first, I assumed it was mplayer, VLC, or QuickTime player, all of which will disable the screensaver while they are doing their magic. Especially the first, which is installed via Homebrew and isn't properly written for OSX. However, much playing with these indicated they're not the problem.
Later, I guessed it was my attached bluetooth devices. So I've performed two experiments:
- I turned on my screensaver then powered off both the keyboard and trackpad, which are the only two input devices attached to bluetooth, yet the problem persists.
- I plugged in a USB mouse/keyboard then turned bluetooth off entirely from the OSX menu bar item. The problem persist even with bluetooth turned off entirely.
After some time, I guessed it was a USB device. I have several USB items plugged in, including several hard drives, a vape pen, and Android device. Unplugging these made no difference.
Finally, after the problem had been going on for several days, Firefox needed a security update and a restart. After restarting it, the screensaver/display sleep worked properly.
Now, whenever I have the problem, if I quit Firefox, the problem goes away. If I restart Firefox, sometimes the problem goes away, but sometimes it persists.
I have NO IDEA why Firefox would be triggering this, and if it weren't for the above facts, I wouldn't really believe it myself. If anyone else has this problem and uses Firefox, please try to corroborate?
The image file is stored in Macintosh-HD:Library:Caches:
There will only be like 3 files there so it should be easy to find.
You can take this file and edit it in an image editor such as GIMP(free) or Photoshop(not free) etc.
Don't forget to make sure that the image keeps it's name or OSX will get confused.
You may also need to use the original image, if, you want to blur it down.
Hope this helps!
Best Answer
I found this article online, and I hope this helps. I just saw someone who had their lock screen be un-blurred, and I started researching it. So, I saw this and created an account on StackExchange to post this. I hope this helps. I am also new to StackExchange, so if the answer could be changed for the better please let me know so I can change it.
Here is the link
If you’d rather your login screen not be blurred, you can do that too! I recommend first adding a custom image to your desktop so that there is an image in so that there is an image in the /Library/Caches folder.Then, copy that image to your desktop by dragging it there.
We’ll use this image in a little bit. First, open whatever image you’d like to show up behind your login screen with Preview. Select the entire canvas (Command+A), then copy it (Command+C).
Next, head to your desktop and open the file you copied from /Library/Caches. Paste (Command+V) what you just copied.
You will need to move and resize what you’re pasting quite a bit in order to get everything just right. When you’re done, save the image (Command+S). Head back to your desktop, and drag your edited image to the /Library/Caches folder. You will be asked if you’d like to replace the file that’s there; click “Replace.”
You’ve now placed your custom background image. Go ahead and log out of your user account to see how it looks:
It worked! In my case, however, the white maple leaf is making it hard to read the white text used by macOS. To fix this, I found a different version of this image where the leaf is blue.
Much better! This version puts the darker part of the image behind the text, which makes it easier to read everything. You’ll probably have to experiment with this a little yourself, but to avoid problems favor dark images over light ones, and simple images over complex ones.
If you’re a Photoshop guru, you might prefer making an image yourself over messing around with Preview in this way. You can do that, but the image you create needs to meet specific criteria. It must be: