Do I have to be online when the giveaway is over ?

You don't need to be online. But you need to leave the feedback, to confirm that the giver sent or not the game

http://www.steamgifts.com/about/faq

If I win a gift, when can I expect to receive it?

• Giveaway creators are allowed one week to send the gift after the giveaway has ended. Depending on the type of gift and the giveaway creator, you might receive the gift to the e-mail address you have listed on the account page, a key might be added beside the gift you won, or the giveaway creator might have sent you a friend request on Steam to make the exchange. Please remain patient, and do not contact the giveaway creator during this time. If the gift is not received after one week, you can mark the gift as not received, and attempt to contact the giveaway creator on Steam to follow-up.

depends on gaben's mood.

You don't need to be online, You have 7 days to deliver your game to the winner, if you don't do it in 7 days the winner will mark as "not received".

If your game is a steam key, you can make it barely automatic to the winner. The new SteamGifts allows you to introduce a Steam Key so the winner can redeem it easier.

I hope it helped.

If you're not online when it ends, and you don't GET online quickly enough, Lord High Most Holy GabeN may just take your game for himself...that's how he sustains himself these days, no food or drink, no oxygen, just game keys

Yeah, I was only worried about the giveaway system. Because sometimes in giveaways from Twitch streamers, the game is automatically given to someone else if you didn't claim it within 1 minute of the giveaway ending o.o Shanx people (y)

Just came here to bring some potatoes.
Yeah.

thanks for the potatoes ^^