Quartile reporting breaks a video ad's completion into four checkpoints — 25%, 50%, 75%, and 100% — tracked via VAST event beacons fired when the video player reaches each threshold. It is the standard video measurement framework across all digital video (VAST-delivered display, mobile, and CTV) and is how DSPs, SSPs, and ad servers report video delivery. In CTV specifically, quartile data is most useful for diagnosing creative performance and technical delivery issues — the two primary drivers of drop-off on a non-skippable format.
How quartile beacons work technically
Each VAST tag includes event tracking URLs for the standard VAST events: start, firstQuartile, midpoint, thirdQuartile, and complete. When the video player reaches each checkpoint, it fires an HTTP GET request to the tracking URL. The DSP or ad server records the beacon fire as a measured event.
On CTV with SSAI, beacons are fired server-side — the ad insertion server sends the beacons rather than the viewer's device. This eliminates beacon loss from network interruptions on the device side and is why SSAI-delivered CTV shows better quartile completion consistency than CSAI-delivered inventory.
Reading quartile drop-off patterns
In a healthy non-skippable CTV campaign, quartile completion should be nearly flat — 97–100% at each checkpoint. Significant drop-off at any point signals a specific problem:
- Large drop between start and Q1 (25%): Buffering or VAST timeout at ad load. The video began but stalled. Most common in CSAI environments with slow creative CDN delivery. Fix: check creative file size (target under 5MB for 30s), ensure CDN is geographically close to India viewers.
- Drop at midpoint (50%): Content abandonment — the viewer left the content mid-stream, taking the mid-roll ad with them. More common in long-form content mid-rolls than pre-rolls. Less controllable by the buyer.
- Drop between Q3 (75%) and completion (100%): Creative issue. The viewer was present but stopped watching in the final seconds. Common when the CTA appears too early and the closing seconds feel redundant. Creative recommendation: hold the brand or product reveal until Q3, keep the final 5 seconds purposeful.
- Uniform drop at all quartiles (e.g., Q1: 90%, Q2: 80%, Q3: 70%, complete: 60%): Systematic beacon loss — likely a tracking implementation issue rather than real drop-off. Check VAST error rates and beacon fire confirmation with the publisher's ad ops team.
Quartile data for creative optimisation in India
India CTV creative norms differ from global conventions in ways that affect quartile performance:
- Hindi/regional language creative: Ads in Hindi or regional languages consistently outperform English-only creative on VCR and Q3-to-completion rates on India CTV. The drop-off between Q3 and completion on English-only ads is 3–5 percentage points higher than on Hindi ads — viewers are present but less engaged with language-mismatched creative.
- Celebrity appearance timing: India audiences respond strongly to celebrity appearances in ads. If the celebrity appears in the first 5 seconds (Q1), Q1-to-midpoint retention improves. If the celebrity appears only at the end (after Q3), the preceding seconds have higher drop-off risk.
- Ad length: 15-second ads on India CTV show near-flat quartile curves. 30-second ads show a midpoint dip of 2–4 percentage points. 45-second or longer ads are uncommon in India CTV programmatic and should be avoided unless the publisher supports them natively.