9 Ways to Maximize Fill Rates Across Web, App, and CTV Platforms

Fill rate is one of those metrics every publisher tracks but few truly understand. On the surface, it’s just the percentage of impressions filled with ads. In reality, it’s a reflection of demand confidence in your supply.

Getting to “100% fill” isn’t the goal. If you’re filling every slot with low-value or non-transparent demand, you’re inflating numbers while devaluing your inventory. The real goal is to maximize fill rate with competitive buyers, across every environment: web, app, and CTV.

Here are nine advanced ways to do it the things experienced publishers still overlook, and where the biggest leaks usually happen.

1. Stop Letting Empty Impressions Slip Through

Empty impressions aren’t harmless. They drag down viewability, frustrate users, and signal weak supply to exchanges. Yet, even large publishers let them slip through when bidders time out or SSPs pass back.

Where it goes wrong:

• GAM returns a blank because no line item is set up for passback.
• Prebid doesn’t trigger fallback creatives.
• On CTV, pod breaks aren’t filled completely, leaving dead air.

Example: One mid-sized publisher left 2–3% of impressions unfilled because their GAM line items weren’t chained to a backup. At 50M impressions/month, that’s 1.5M empty calls and thousands in lost programmatic revenue.

Fix:

• Use GAM passback line items or house ads to catch unfilled impressions.
• In Prebid, configure a default line item with safe fallback creatives.
• On CTV, structure pods with guaranteed backup campaigns.

Even if your fallback is a house ad, it’s better than serving nothing. Buyers see a clean, fully filled auction, and your site looks trustworthy.

2. Segment Demand by Platform Don’t Mix Web with CTV

A common mistake is lumping all supply together. Buyers hate it. Web, mobile app, and CTV have entirely different buyer logic, auction mechanics, and CPM expectations.

Where it breaks down:

• In-app SDK traffic routed through the same demand paths as desktop → DSPs throttle spend because they can’t parse inventory type.
• CTV bundled with display → buyers underbid because they assume lower quality.

Fix:

• Create separate line items for web, in-app, and CTV.
• Use unique placement IDs and demand paths per platform.
• Send clean signals: device type, app bundle ID, CTV pod metadata.

Result: When buyers see your supply segmented clearly, they assign budget more confidently. One large OTT publisher increased fill by 12% simply by unbundling app and CTV traffic.

3. Set Floors by Geo, Not Just Globally

Global floor pricing is one of the most overlooked killers of fill. A floor that works in the US can wipe out fill entirely in LATAM, India, or SEA.

Example: We saw a publisher running a $2 floor globally. US traffic filled fine. But Tier-2 GEOs (where buyers typically bid $0.50–$1.20) dropped to ~60% fill. The publisher assumed “low demand,” but it was self-inflicted.

Fix:

• Use geo-specific floors in GAM or Prebid.
• Example: $2.50 for US, $1.20 for LATAM, $0.50 for SEA.
• Layer with format-specific rules your CTV floors shouldn’t match mobile banner floors.

Pro tip: Adjust floors dynamically during high-demand events (Q4 holidays, sports seasons). What clears in June won’t clear in December. Geo-based floors ensure you’re maximizing fill globally while protecting CPMs in premium markets.

4. Shorten Timeouts That Waste Fill

Timeouts are often seen as a latency issue, but they directly impact fill rate. Cut them too short and you block bidders who could’ve delivered. Set them too long and you slow down rendering, tanking viewability.

Where publishers slip:

• Running the same timeout across all platforms.
• Ignoring that video/CTV bidders respond slower than display.
• Never revisiting timeout settings after initial setup.

Example:

A video publisher dropped timeout from 2000ms to 1000ms to “speed up load.” They lost 30% of bids from a premium video SSP that responded at ~1300ms. CPMs and fill collapsed until they lengthened video timeouts again.

Fix: Audit response-time distributions:

• 800–1000ms for display.
• 1200–1500ms for mobile.
• 2000ms for video/CTV.

Set timeouts slightly above the 80th percentile. That way you catch most valid bids without dragging out the auction.

5. Lack of Transparency

A less obvious but equally dangerous violation is failing to provide transparency to buyers.

What this includes:

• Missing or inaccurate ads.txt entries.
• No sellers.json disclosure.
• Supply paths without proper s-chain verification.

Buyers rely on these signals to verify your inventory is legitimate. Without them, your supply looks suspicious even if your traffic is clean.

This isn’t just about compliance with Google AdSense policy. It’s about building trust across the open auction. Demand platforms increasingly refuse to transact with publishers who don’t provide full transparency.

How to fix it: Keep your ads.txt file updated with every active partner. Ensure your sellers.json lists your business details clearly. And confirm your demand partners pass full s-chain data downstream. These are small technical steps, but they prevent your inventory from being excluded by default.

How to Stay Compliant and Competitive

Policy mistakes aren’t minor slip-ups they’re existential risks and the toughest part is that most publishers don’t even realize they’ve crossed a line until the “limited ads” warning shows up in their dashboard.

The truth is, one ad policy violation can trigger a chain reaction: demand partners start pulling back, advertiser trust drops, and your revenue flow weakens fast. The safest path is staying proactive. Regular audits, transparent setups, and close attention to traffic quality are what keep exchanges confident in your inventory.

And if you’re unsure where your blind spots are, that’s where an outside perspective helps. At MagicBid, we work with publishers every day to keep their setups clean, compliant, and future-proof because in this space, prevention is the only real protection.

If you’re not making the most of your ad space, you’re leaving money on the table. MagicBid helps web, app, and CTV publishers maximize revenue with smarter ad placement and optimization tools.

• Web Monetization: Get better ad visibility, higher engagement, and more revenue from every impression.
• In-App Monetization: Connect with premium advertisers to effortlessly boost fill rates and eCPMs.
• CTV Monetization: Deliver high-quality, tailored ad experiences that keep viewers engaged and advertisers paying more.

With MagicBid’s advanced ad tech and expert support, you can turn your traffic into higher earnings without the guesswork. Connect with us now to get a free ad revenue evaluation.