Just now I checked on my computer and there is no lag with a 4.21GB folder with 1393 GIFs I loaded:
(Right-click open image in a new tab to see it fully)
What computer are you using, what web browser and what operating system?
For reference, I'm using an ASUS A15 Tuf Gaming Laptop (mid-range consumer PC specs), on Firefox, Windows 11.
The offline and online versions are identical, so the performance issues might be due to your computer.
Hmm, your specs should be fine, a 5600G with 32GB is plenty, and the GPU isn't really involved here.
Very likely the Chrome/Firefox difference you noticed might be the biggest issue. The app plays each GIF as a normal <img> and lets the browser animate it, and Chrome handles many simultaneous animated GIFs much worse than Firefox does; it's main-thread work, so it's a browser architecture thing rather than a hardware thing.
Two things worth checking in Chrome: make sure hardware acceleration is on (chrome://settings/system), and have a look at chrome://gpu to see whether it's fallen back to software rendering — that would make it much worse than normal.
Also, how big are your GIFs in pixel dimensions? 70 large ones (say 800×600+) is a lot more per-frame work than 70 small ones, and that matters more than how many are in the folder. If they're big, shrinking the window or zooming out so fewer are visible at once will help a lot, as will the pause-all button.
Also, how heavy filesize (mb) wise are those gifs? I'm trying to see in the code if there are some kind of optimizations I could do that would make it work better with particularly heavy gifs if they happen to be cause of lag.
The 1393 gifs I tried are all 400x400px in resolution, roughly 1-6mb in filesize, but I also tried a folder with 121 gifs that were 800x700px/1-6mb in size and those ran fairly smooth in both firefox and brave browser.
One thing I forgot to mention is that all my gifs I've tested were optimized with Gifski: https://reactorcore.itch.io/easy-bulk-gif-optimizer
This might also affect the stuttering you had on your end if your gifs we're raw/unoptimized.
