Viewability percentage measures the proportion of an ad that is actually seen by users, rather than just served on a page or in an app.
1. Viewability Percentage – What is it?
- By industry standards (IAB)
- Display ads: For 1 continuous second at least 50% of pixels have to be in the view of the user.
- Video ads: For 2 continuous seconds at least 50% of pixels have to be in the view of the user.
- Viewability percentage = Number of viewable impressions/(Total measured impressions) x 100
Example:
If 70 out of 100 ads meet the viewability standard → 70% viewability rate.
2. Why it’s important?
A. ROI for the Advertiser and Media Efficiency
- There are cases where an ad can be “served” but not seen (e.g., if the user never scrolls down and the ad is below the fold).
- Paying for unseen impressions is the one of the quickest ways for wasting budget.
- High viewability increases the likelihood of:
- User attention
- Engagement
- Conversion actions
B. Industry Standard for Quality
- A lot advertisers now are looking for minimum viewability (e.g., >70%) in contracts.
- Inventories with low viewability struggle to sell at higher rates.
C. Better Campaign Optimization
- Tracking viewability allows advertisers:
- Shift or adjust the spend to high-performing placements.
- Identify poor placements (e.g., certain sites, apps, ad slots, formats).
- Viewability data can be layered with engagement and conversion metrics for smarter bidding.
D. Fraud Prevention
- Viewability tracking helps detect:
- Ads hidden behind other elements
- Non-human traffic (bots)
- Combats invalid impressions.
E. Impact on Brand Reputation
- Low viewability often points to that the ads might be showing in overfilled, low-quality placements.
- High viewability is often correlated with better brand results in terms of perception and conversion.
3. How viewability affects the digital ad ecosystem?
- Advertisers: Demand high viewability to justify spend.
- Publishers: Adjust and improve their site/app design or layout in order to make ad slots more visible.
- Programmatic Platforms: Integrate viewability as a bidding parameter.
- KPIs: Many people now are going away from the standard CPM rates and start optimize toward vCPM (cost per thousand viewable impressions).
Bottom line:
High viewability by its own doesn’t guarantee results (users can ignore an ad), but low viewability almost guarantees wasted spend. If an advertiser is looking for foundational quality metric in modern digital advertising and a key input for performance optimization viewability is a crucial one.
Example: Two Campaign Placements
You run a campaign with $10,000 budget and buy 1,000,000 impressions at a CPM (cost per thousand) of $10.
| Placement | Impressions Bought | CPM | Total Cost |
| A | 1 000 000 | $10 | $10,000 |
| B | 1 000 000 | $10 | $10,000 |
Step 1: Viewability Rates
- Placement A viewability: 80%
- Placement B viewability: 40%
Step 2: Viewable Impressions
Viewable Impressions = Impressions Bought × Viewability Rate
- A: 1 000 000 × 0.80 = 800 000 viewable impressions
- B: 1 000 000 × 0.40 = 400 000 viewable impressions
Step 3: Cost Per Viewable Impression (vCPM)
- A:
- B:
Step 4: Key Insight
- On paper, both placements look the same: $10 CPM, however, in reality Placement A delivers twice the visibility at half the vCPM. Choosing inventory with higher viewability means you will likely spend less for the same amount of actually seen ads.
✅ Takeaway:
Taking into account viewability percentage makes campaigns more efficient and ensures you’re paying for impressions that have a real chance to influence your targeted audience.
Integrating viewability into Media buying
1. Use Viewability as a Bid Filter
Most DSPs (Demand-Side Platforms) allows you to set minimum viewability thresholds before engaging in auctions.
- Rule example: Only bid on inventory with historical viewability > 70%
- Based on past performance data from measurement vendors such thresholds can usually be applied.
2. Bid on vCPM, Not CPM
You can choose vCPM bidding, instead of paying per 1000 served impressions (CPM):
- vCPM means you only pay for viewable impressions.
- Example: If CPM is $10 with 50% viewability, the system would automatically adjust, so your effective cost per viewable impression stays competitive.
3. Apply Pre-Bid Viewability Segments
Many measurement vendors are able to provide pre-bid segments, so you can plug into your targeting. These ensure ads are placed where historical data predicts higher viewability percentage.
4. Combine with Format & Placement Rules
High viewability often correlates with:
- Above-the-fold display units
- Sticky/fixed position ads
- Larger ad sizes (300×600, 970×250, outstream video)
You can exclude formats and placements with historically low viewability (e.g., banners below-the-fold).
5. Optimize with Post-Bid Reporting
Even with pre-bid filters, track post-bid viewability reports:
- Identify publishers/placements which are underperforming
- Shift spending to high performers
- Adjust your minimum viewability percentage as you learn more.
Pro Tip:
Use viewability + engagement metrics in your bidding logic. For example:
“Bid higher if viewability > 80% and click-through rate > 0.15%.”
That way you’re chasing visible ads that actually perform and not just chasing visible ads.
If you are about to launch your first campaign or you want to optimize and apply some new logic in your advertising strategies, reach out to our team at adcorrelation@gmail.com. We will be at your disposal for any type of collaboration.