Operator glossary
Viewability (MRC standard)
The MRC standard for when an ad had an opportunity to be seen — 50% of its pixels in view for one continuous second, two continuous seconds of play for video, 30% for formats 970x250 and larger — and the basis Amazon bills against under vCPM.
MRC's Viewable Ad Impression Measurement Guidelines are version 2.0, from August 18, 2015. A display impression is viewable when at least 50% of the ad's pixels sit in the viewable space of an in-focus browser tab for one continuous second post-render. Formats of 242,500 pixels or more — a 970x250 and up — drop to a 30% threshold; video needs two continuous seconds of play at the same pixel requirement. Amazon does not restate that: its performance-metrics page says an image is viewable when at least 50% is visible for at least 1 second and calls that the MRC definition — no pixels, no in-focus tab, no large-format carve-out. That paraphrase is what vCPM bills against, on Sponsored Display's Optimize for reach and Sponsored Brands' Grow brand impression share.
The rate every agency deck computes — viewable divided by impressions — is not MRC's, which divides viewable by measured; Amazon's own viewability guide prints the same formula. But measurableImpressions and measurableRate exist only on dspCampaign and dspInventory reports, so on Sponsored Brands and Sponsored Display any rate you compute books every undetermined impression as a miss, and it moves when Amazon's measurement coverage moves, not when your placements do. Column names compound it: the API documents viewabilityRate as view-through rate, views divided by impressions, and Sponsored Display's MRC column is impressionsViews, not viewableImpressions. MRC's accreditation chart lists Amazon under Sponsored Products and DSP only, and both first-party and third-party (IAS, DoubleVerify) accreditation is scoped to DSP inventory. Amazon publishes the definition for sponsored ads but not the measurement methodology.
The numbers
- MRC's Viewable Ad Impression Measurement Guidelines, Version 2.0 (August 18, 2015), require 50% of an ad's pixels in the viewable space of an in-focus browser tab for one continuous second — 30% for formats of 242,500 pixels or greater, two continuous seconds for video.
- Amazon's performance-metrics page paraphrases that as 50% visible for 1 second (2 seconds playing for video), labels it the MRC definition, and defines vCPM as spend divided by viewable impressions, bid per 1000 viewable impressions.
- In the Amazon Ads API version 3 columns reference, viewabilityRate is documented as view-through rate (views divided by impressions), Sponsored Display uses impressionsViews rather than viewableImpressions, and measurableImpressions appears only on dspCampaign and dspInventory reports.
Primary sources: Amazon Ads help center — Performance metrics (viewable impressions, vCPM, 3-day cost update) · Amazon Ads — Viewability guide (viewable/measured formula, 30% large-ad threshold) · Amazon Ads API — Reporting columns (version 3)