Most canned cranberry sauce doesn't contain obvious animal ingredients, but of course, it has sugar in it and some brands of sugar are not vegan, so it's always worth checking with the manufacturer. I've also heard (although never seen myself) that some of the jellied kinds can contain gelatin which would make them non-vegan. Worth a mention too is that some of the higher-end jars of cranberry sauce can sometimes contain honey or alcohol. Honey makes them automatically not vegan, and the alcohol again depends on what was used. Some wines, ports and sherries are vegan and some aren't. So basically there is no straight answer, but making your own takes any doubt out of the equation though. And the added bonus is it tastes a million times better, and you avoid having to slide that unpleasant jiggly cylinder of sauce out of the can!