Hey anon, thanks for the ask!
I actually use a site called glitterboo.com for all my glitter giffing needs. You can use it for free, however your options are very limited on picture size and the types of effects you can use. A year long subscription is $8.99 and gives you free range of all available options. I’ll show you how to use this site through the free version.
So first you wanna go to glitterboo.com and go to “Click here to start”
from here you can choose a photo to upload by either browsing your computer or copy+pasting a url link from the web (for this free version it makes you choose what kind of effects you want before you can get started, however with the paid version you’ll have all these options available to you after you’ve uploaded your photo)
okay so now you’ve got your photo uploaded and you’re ready to add some sparkles!
the brush you use to add sparkles is a flower shape that changes the photo purple to indicate the areas you’ve chosen to add effects. The program automatically places the effects in high-contrast areas, so deciding what kinds of sparkles to use and where and for what kinds of pictures will take some trial and error.
Fiddling with the many settings will also take some practice to get the kind of effects you’re looking for with the kind of picture you’ve decided to work with. For example, pictures of low-contrast 2d animation are a lot harder to work with than real life photos from movies, etc.
Under “selected area” is where you can change the size of your brush or choose to erase any areas you want to deselect.
After you’ve decided where to add your effects you can go over to “animation” to preview a small portion of the picture. You can move this window around to preview different parts of your photo.
once you’ve perfected your glittering masterpiece you go down to “view/download” to choose your sizing. Again the free version is very limiting so you won’t have many options here.
However once you’ve finished adding effects, determined the size you want your picture to be, and have download it—ta-da!