You can create a custom event in Google Tag Manager that fires every time a visitor spends at least 30 seconds on a page of your website.
This is valuable for the following reasons:
1. Reporting. You're driving traffic to your website, but is it quality traffic? How many of those clicks are resulting in at least 30-second visits?
2. Optimization. I've seen and heard of mixed results with this, but it's a great alternative to optimizing for link clicks or landing page views when trying to drive traffic. Try to get Facebook to focus on longer visits rather than a simple click.
3. Targeting. Create a custom audience of those people who spend at least 30 seconds on a page of your website and target them with your ads.
Get creative!
