This one clearly is pixelart, but was saved as a JPG instead of a png. Once you zoom in you see that the sharp pixels got destroyed because of the filetype you chose for saving.
It's best to save pixelarts either as pngs (generally a good idea), gifs (<256 colors, might cause problems on some websites though, but necessary for animations) or bitmaps (super inefficient way).
SO I'd suggest in future save pixelarts as pngs and the outcome will be exactly the same as you saw during creating it in the software.
Ok, thank you, I'll try to save them as pngs in the future