Is it appropriate to remind a gifter you won his giveaway?

If it's a dev giveaway the key should be listed on your "won giveaway" list.

Dev should come by email/what the guy above me said.

Isn't a key.

I found out the user is a developer because of his Steam name and profile.

If it's not marked as "developer giveaway" it's just a "normal" giveaway....I don't see why you should not remind him (kindly, of course) that you won...it's not begging to me

You should remind him or contact the support .Since you won that giveaway it won't look like you're begging him ,you deserve that gift. ;) check your email even your junk folder btw ( i have won too in the past and the keys/gifts came over there)

Wait a couple days more.

Maybe he forgot. If he's an upstanding citizen of Steamgifts, I see no harm in dropping him an email to let him know you're the winner and didn't receive anything yet.

I see nothing bad in this.

I have one guy who got a code per mail almost one week ago, he logged in some hours ago but still didnt mark it as recieved...

If you win it's no more than fair to just add someone and inform them you won their giveaway.
Only makes it easier for the other person to deliver.
And if he cannot, at least you know it, rather than having to wait indefinitely hoping he'll come through.

If it's been over 3 days, and he never mentioned anything about being late, a small push is OK.

isn't dev giveaways keys ?

Added him exactly 1 day ago and he ignored my invite. I guess i'll wait 2 more days and then mark it as not received. I hope it's not calling out - i'm talking about this giveaway (the guy who marked it as received obviously have no idea how sg works, he also didn't received it).