Can you write a review for a game you don't own?

If the Steam game isn't in your Steam account library, you can't write a review for it, period.

Q. Do I need to have purchased a game in order to write a review of it?

A. Purchase is not required. You may write a review for any product in your Steam account. Whether you registered a Steam key obtained elsewhere, or played a free game, you will be able to write a review for that product. Your playtime in that game or time in that software title will appear next to your review.

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