The Ad Library provides a searchable collection of all of the ads which are running, or have run, on Facebook and/or Instagram.
If you're struggling for ideas of creative content for your Facebook ad, then a quick browse of the ad library could give you the inspiration you need.
Just input your keyword search term and see the display ads that contain matching text. You can filter the search by country and whether the ads are active or inactive. Even more, you can search on a specific page to see its ad history.
Here's a search we ran against "Stressless":
You can check out the library here.
The “Home” tab of every Facebook Page also now has a “Page Transparency” section where you can access the ad library of a specific page.