Advertising Inventory
Advertising inventory is the total number of ad placements available on a platform at any given time. Think of it as "shelf space" for ads.
Every time someone scrolls their Facebook feed, watches a YouTube video, or browses a website, ad slots become available. That's inventory.
Why inventory matters:
The bidding system that determines your CPM is directly tied to inventory. More inventory = lower costs. Less inventory = higher costs.
What affects inventory:
- User activity: More people online = more ad slots = more inventory
- Platform policies: Limits on ads per page affect available slots
- Time of day: Peak hours have more inventory
- Seasonality: Holidays see more users but also more advertisers competing
Example: During Black Friday, there are more users online (more inventory), but there are also 10x more advertisers competing for those slots. The demand spike outpaces supply, so CPMs skyrocket.
Frequently Asked Questions
Supply and demand. When inventory is limited (fewer ad slots) and demand is high (many advertisers competing), prices go up. During holidays or major events, inventory becomes scarce and CPMs spike.
Your ads won't be shown. Platforms prioritize higher-bidding advertisers. If you're outbid, your reach drops. This is why costs increase during competitive periods like Black Friday.