How to check whether you have a bundle game?

https://www.steamgifts.com/bundle-games
make a fav button

https://steamgifts.com/bundle-games

Keep in mind that just 1 user keeps the list up to date, so a game not on the list might get retroactively bundled, if it has been in a bundle or is in a bundle at the moment. Also games with high discounts might get added to the list.
Search the forum for similar threads for more information.

Edit: Please keep also in mind that Steamgifts can not check if you have given a key or a gift.

Another method - https://www.steamgifts.com/discussion/l6RDh/userscript-sg-game-tags-show-some-info-of-the-game-cards-achievement-bundled-etc/search?page=4

There's also enhanced Steam that sort of works - http://www.enhancedsteam.com/
It lists on the Steam store page if a game has been in a bundle. The thing is, sometimes games from the highest tier of Humble Bundles do not go on the bundle list here at SG, and sometimes games get bundled when they were never in one if they go on sale at too low a price. It also categorises things like IndieGameStand deals as bundles,when they don't tend to count as one here.

Games being 90% or more off on steam & other official stores (not resellers) get on the bundle list, too.

So if I giveaway a game that has been on sale for 90% it will be considered as a bundle game yet a game that has been on sale for 80% will not be considered a bundled game?

Thanks for all the help guys really appreciate it
I guess I'll just give away games independent of their bundled/non-bundled status, I only go on this website a few times a week
Btw - make sure you join my current give away's