What is Backfill?
Backfill is a feature that automatically connects multiple ad sources to fill gaps when there are no high-priced direct deal ad bookings, ensuring continuous ad delivery. Combined with Adrop’s unique bidding and waterfall optimization technology, it simultaneously increases ad pricing (eCPM) and Fill Rate while providing more stable revenue growth.- Automatically connects multiple global ad sources
- Optimizes pricing through Adrop’s unique bidding and waterfall optimization strategy
- Secures optimal pricing (eCPM) and Fill Rate by country, placement, and time zone
- Applies after periodic performance A/B testing
The key is to continuously increase overall eCPM while growing direct ad proportion. Ad Control allows you to manage this process on a single platform.
Why Do You Need Backfill?
Direct Ads Alone Have Limitations
Direct deals have high pricing but struggle to fill all inventory.Network Ads Alone Are Also Insufficient
Network ads like AdMob and AppLovin fill empty inventory, but pricing has limits no matter how optimized. Competition among network ads alone cannot dramatically increase eCPM.True Monetization Is Their Combination
| Ad Type | Advantages | Disadvantages |
|---|---|---|
| Direct Ads | High pricing | Fill Rate limitations |
| Network Ads | High Fill Rate | Pricing limitations |
| Direct + Backfill | High Pricing + High Fill Rate | - |
How It Works
1
Ad Request
An ad request occurs from the app.
2
Check Direct Ads
Checks if there are booked direct ads.
3
Ad Display
Direct Ads Available
Display Direct AdsMaximize revenue with high pricing
No Direct Ads
Display Backfill AdsStable monetization even for empty inventory
Direct ads display first, and Backfill ads only display when there are no direct ads. You can monetize even empty inventory while protecting direct ad revenue.
Activating

Activation Process
1
Select Unit
Select the target unit from the Ad Units menu.
2
Activate Backfill
Click the Turn On Backfill button on the detail page.
3
Confirm SDK Integration
Select whether Web SDK integration is complete.
4
Wait for Connection
After request, status changes to Processing. Monetization starts automatically when connection completes.
Upon first activation request, a representative will contact you for optimized operation of direct and Backfill ads.
Pause and Restart
Backfill ads can be paused and restarted at any time.- Status changes are reflected within maximum 30 minutes.
- Does not affect direct ad campaigns.
Supported Formats
| Formats | Backfill Support | Notes |
|---|---|---|
| Banner | O | |
| Interstitial | O | |
| Rewarded | O | |
| Native | O | Headline or image required |
| Popup | △ | Support planned |
| Splash | X | Direct ads only |
Native Unit Cautions
- Additional text items (subtitles, etc.) do not display in Backfill ads.
- Must register headline or image for Backfill ads to display.
Checking Performance
Backfill ad performance can be checked in the Reports > Backfill tab.| Metric | Description |
|---|---|
| Impressions | Number of times Backfill ads were displayed |
| Fill Rate | Display rate vs. ad requests |
| Clicks | Number of Backfill ad clicks |
| CTR | Click rate (clicks / impressions) |
| CPC | Revenue per click |
| eCPM | Revenue per 1,000 impressions |
| Revenue | Revenue generated from Backfill ads |
Monetization Strategy
1
Secure Base Revenue with Backfill
Activate Backfill ads to secure baseline revenue from all inventory. Empty ad time disappears.
2
Increase Revenue with Direct Ads
Register Ad Products and attract advertisers. When direct ads come in, revenue increases with pricing higher than Backfill.
3
Optimize Portfolio
Analyze the ratio of direct ads to Backfill ads in reports, and concentrate direct ad sales efforts on high-profitability units.
Next Steps
Ad Product Settings
Check how to bundle Ad Units to sell as Ad Products.
FAQ
What happens to existing Backfill ads when direct ads come in?
What happens to existing Backfill ads when direct ads come in?
Direct ads automatically display first, and Backfill only fills inventory without direct ads. No manual switching work required. With other solutions, developers must modify code each time direct ads come in, but Ad Control automatically coordinates direct ads and Backfill within a single Ad Unit.
Can I use it together with other network ads?
Can I use it together with other network ads?
Not recommended. Unifying with Ad Control Ad Units allows real-time switching between direct ads and network ads to maximize revenue. Mixing multiple solutions consumes unnecessary resources in operations and development, and you can’t enjoy the benefits of integrated reporting and optimization. To seriously expand your ad business, managing direct ads and Backfill together on one platform is efficient.
Direct ad sales are difficult - can I use only Backfill first?
Direct ad sales are difficult - can I use only Backfill first?
Actually recommended. Start monetization with Backfill first while accumulating traffic data. This data becomes powerful negotiation material during direct ad sales. Once advertisers are secured, just register Ad Products in Console. You can switch to direct ad monetization immediately without separate development.
Why are direct ad prices much higher than Backfill?
Why are direct ad prices much higher than Backfill?
Network ads have pricing limits because they receive ads displayed simultaneously on multiple apps through auction. In contrast, direct ads can receive premium pricing as advertisers purchase specific apps and placements. Securing base revenue with Backfill while increasing direct ad proportion is the key to revenue maximization.