でも details

Examples

but; still — objects to, or qualifies, what was just said

もう十二時じゅうにじだよ。でも、全然ぜんぜん眠ねむくない。

mou juuniji da yo. demo, zenzen nemukunai.

It's already midnight. But I'm not sleepy at all. casual

電車でんしゃが止とまっていました。でも、なんとか間まに合あいました。

densha ga tomatte imashita. demo, nantoka ma ni aimashita.

The trains had stopped. Still, I somehow made it in time. neutral

お気持きもちはよく分わかります。でも、今回こんかいは日程にっていを変かえられません。

o kimochi wa yoku wakarimasu. demo, konkai wa nittei o kaeraremasen.

I understand how you feel. But we can't change the schedule this time. neutral

しかし
Pure register — でも is the conversational default and is at home in chat and casual mail, while しかし belongs to writing and prepared speech; でも in an essay reads slack, and しかし in ordinary chat reads like a lecture.
けど
Position, not meaning — けど closes the clause it contrasts and keeps both halves in one sentence (高たかいけど買かった), while でも needs the first half already finished and opens the next sentence; でも cannot sit after a predicate the way けど does.

ても
The same でも splits on what precedes it — after a noun or na-stem it is ても's copular half, "even" (子供こどもでも分わかる); at the head of a sentence, with nothing before it at all, it is this contrast connective.