运营者术语表

Viewability（广告可见度）

MRC 定的可见展示口径：展示类广告至少 50% 像素在可视区域内连续停留 1 秒，视频要在同样 50% 的条件下连续播放 2 秒；Amazon 的 vCPM 就是按这个口径计费的。

Amazon 帮助页只把 MRC 口径转述成「至少 50% 可见满 1 秒」，没提像素、没提 in-focus tab、没提「连续」，也没提大尺寸只要 30% 的例外。真正要盯的是分母：MRC 的 viewable rate 是 viewable ÷ measured，而 measurableImpressions 只出现在 DSP 报表里，SB、SD 只能拿 impressions 当分母，等于把无法判定的展示都计成不可见，数字波动往往是 Amazon 的测量覆盖变了，不是你的 placement 变了。列名也骗人：viewabilityRate 官方写的是 view-through rate，SD 的对应列叫 impressionsViews。MRC 的平台认证表只列了 Amazon 的 Sponsored Products 和 DSP，第三方验证也只对接 DSP 库存；Amazon 对 sponsored ads 公布了定义，但没公布测量方法。

关键数字

费率与规则以官方英文原文为准，保留原文：

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.

官方来源：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)