Pick the constraint before changing the picture
A GIF for a small reply, a website walkthrough, and an email attachment each has a different job. First find out whether the destination is rejecting the file size, the pixel dimensions, or the format. Common upload limits vary between services, account types, and uses such as avatars or attachments. Check the receiving screen rather than assuming that a file accepted somewhere else will also work here.
Three things that make an animation heavy
Colors describe the shades available to each frame. Reducing them can help with a cartoon or a flat interface, while a photograph may show rough gradients. Dimensions determine how many pixels each frame needs. Frames determine how many pictures must be stored across the animation. Lowering all three at once may save bytes, but makes it hard to see which change damaged the result.
The GIF compressor starts with a palette test. If you have an attachment budget, enter a target in KB or MB; this makes the optional dimension and frame reduction switches available. Decide which changes the message can tolerate, then check the result and any missed-target notice. If the source is a video, a shorter interval in the video converter removes unnecessary material before the GIF is created.
Use the size comparison as a decision
Compression is an experiment, not a fixed percentage discount. Texture, camera movement, and colors that change across the frame influence the outcome. The compressor reduces redundant frame data and uses a shared palette when suitable. If your chosen color count cannot save bytes, it automatically tests fewer colors. If those attempts do not help, it returns the original unchanged and shows a notice, so the result is never larger than the source GIF. Check the preview: fewer colors may still affect important details. GifSlim keeps the workflow focused on this decision: do the saved bytes justify what changed on screen?