TLDR: Just like Facebook’s Ads Library, Google also allows you take a peek into your competitors ads.
How to use Google’s built-in tools to spy on your competitors.
Google’s Ad Transparency Page
This is a free alternative to getting a glimpse into your competitors advertisements. However, it’s a little tricky to get started as you need to be served an ad first. Start by doing some light searching for the keywords you think your competitor are advertising for.
Pro tip: Try searching the companies name. Most time there is a branded campaign around the name.
For this example, I’m going to start on YouTube.
Once you have an ad served to you, you should see a small ℹ️ icon next to the ad.
From there look for the section “About this advertiser”
Click "See more ads"
Whala! You’re in.
Bonus
Use the “filters” button to look date ranges, location, media type, and much more.