Good question. It basically depends on the format and the way they were originally exported/produced.
JPG images are uploaded flawlessly, with the same image quality as the original.
PNG files are handled a bit differently. Depending on how they were exported or produced, they can gain weight or loose quality when uploaded to Breezi. Right now we’re doing the best to find a balance between weight and balance.
As for GIFs, it’s similar to JPG, they are uploaded with the same quality as they were exported. But if they are very compressed (optimized), it’s very likely to loose information and quality. However, if they were exported without a lot of compression, they should come out alright.