How to reduce size of animated gif image?

How to reduce size of animated gif image? Is there any online tools available? Need suggestion.

 

What are you making these in?

First, try to make whatever actually changes in each frame be the only info on that frame (if possible)-- for example, if a cat sits and wags its tail, thus only the tail moves, your bottom frame is whole cat, but the others are transparent frames with only the new tail.

In GIMP (and I assume then of course Photoshop) there is a tool called "Optimise" or Optimise for Gif" (goto Filters, Animations, Optimise for Gif) which does the same thing, except not smartly.

Your bottom frame is the fullest frame, and it will stay showing, with the changes sitting on top. If you want something to disappear, then you can copy just the size you need from the bottom frame to cover whatever's disappearing.

Also you can try to lower the number of colors in your animation. If you're making a new animation, make it in RGB and then when you change it to Indexed Colors (under Image on the GImp toolbar, Photoshop is very similar), tell it you want to manually set the index-- set the number of colors to something small. If the image then looks too crappy, Undo and try again with a few more colors, until it looks okay. Under 70 colors is nice, but if it's like company logo graphics this can be really low number like3 or 5.

Also remember gifs read from left to right starting on top line, so a line of black pixels is smaller filesize than a column. A line: line#1 color=black
a column: line#1 pixel#1 color=black; line#2 pixel#2 color=black; and so on. Not normally useful but sometimes you can use lines of color in place of a gradient.
Hope helps