Exporting animated gif - limiting to the size of artboard

I run into this same issue frequently and found a fix. Before going to export > save for web (legacy), click on you art board. On the toolbar along the top of the viewer there will be a small gear (set art board behaviors). Check mark the box shrink wrap canvas on save. This will make for a smooth export. 

Hi the answer is delete the artboard you have created a gif the an artboard simply right click ungroup artboard this will allow you to keep all your work and not have to redesign the creative again once you have done this you can then crop the gif to the right size I hope this helps?

I would advice to use Export > Artboards to Files, and then record and action and apply to all these files. To my pity, animation doesn't work with artboards.

Save for web has problems with artboards, probably because it’s old and developed before there were artboards. I’m guessing that the exported animated gif is increasing in size because it is ignoring the mask on the background image. Export As was developed to work with artboards, but unfortunately it doesn’t do animated gifs, at least not yet. I think you need to move all of the elements out of the arboard and delete the artboard. Then crop your document if needed to the size required. I expect that save for web will work fine after you do this. Let us know.

Blank Space?  Transparent space  or a solid color border.  The canvas size of the animated gif should be the same size as your document's canvas size or the size you resize the animated gift to.  Save for web does not trim transparency or color borders.