A view-through conversion is a sale, sign-up, install or other goal credited to an advertisement that a person saw but did not click. The person is served a banner, video or sponsored placement, moves on, and later converts through another route, such as a brand search. If that action falls inside a defined period after the impression, the platform records it against the advertisement. The length of that period, the definition of "seen" and the rules for deduplication all vary by vendor, which is why a single campaign can report very different results in different systems.

The metric exists because most display and video advertising is never clicked. Research by comScore, presented in 2008 by its executive chairman Gian Fulgoni, found that two-thirds of internet users clicked no display advertisement at all over a month, and that 16 per cent of users generated 80 per cent of clicks. Counting only clicks left most of the channel's possible effect unrecorded. View-through counting was the industry's answer, and it became the source of one of advertising's longest-running measurement arguments.

How a conversion is matched to an impression

First, an ad server or platform logs an impression against an identifier: a third-party cookie in older web set-ups, a device advertising identifier in apps, or a signed-in account on platforms such as Google, Meta and Amazon. The advertiser's tag, pixel or server-side API then reports a conversion event. A matching job looks backwards from that event for qualifying advertising activity tied to the same identifier. Finally, a ranking decides which activity receives the credit.

That ranking almost always places clicks above views. According to Google's documentation for Demand Gen campaigns, a conversion is recorded once, against the highest ranking event: clicks first, engaged views second, impressions last. Google Ads also excludes from view-through counts anyone who interacted with any of the advertiser's other advertisements. In ChatGPT Ads, OpenAI's documentation states that the click takes precedence when a conversion qualifies for both treatments. Apple goes further, with SKAdNetwork sorting click-through ahead of view-through on the device itself before a single network is declared the winner.

Campaign Manager 360 (CM360), Google's advertiser ad server, exposes the plumbing most plainly. When a page carrying a Floodlight tag loads, the system reads the cookie or device identifier, and an overnight process checks for earlier impressions or clicks inside the conversion window. Unmatched records are discarded. The most recent qualifying click wins, and only where no click exists does the most recent impression take the credit. Window values start at zero, which counts 24 hours, so a setting of one counts 48 hours. The API object behind this, LookbackConfiguration, carries two fields, clickDuration and postImpressionActivitiesDuration, each accepting 0 to 90. According to Google, the Floodlight configuration default is 30 days for both clicks and impressions.

What qualifies as "seen" differs more than most reports acknowledge. For App campaigns, according to Google, a view requires at least 50 per cent of an advertisement's pixels on screen for one second, or two seconds of video. For Demand Gen, the same company's documentation counts a view when at least one pixel appears on screen for any length of time. Amazon moved in the stricter direction early, applying the Media Rating Council (MRC) standard of 50 per cent in view for one second to view-through credit from January 1, 2019. In April 2022 Google let Display & Video 360 (DV360) advertisers limit Floodlight attribution models to viewable impressions.

Windows, columns and a worked example

The window is the main configuration lever. Google Ads defaults the view-through window to one day, adjustable up to 30, against 30 days for clicks and three days for engaged views. For store visits the view-through window is fixed at one day. Meta moved to a seven-day click and one-day view default in January 2021 and still offers a one-day view option. Amazon counted ad views within 14 days until January 2026, and OpenAI launched its version with a window locked at one day.

Where the number lands matters as much as its length. According to Google, view-through conversions in Google Ads appear only in the View-through conversions and All conversions columns and stay outside the main Conversions column, with three exceptions: Performance Max for store goals, App campaigns and Demand Gen, where optimisation can make them biddable. Once biddable, they surface under the Impression value of the Ad event type segment.

A simple case shows the mechanics. An advertiser uses a one-day window and serves a banner on a Monday at 09:00. A purchase at 08:00 on Tuesday, with no click on any of the advertiser's advertisements, counts as a view-through conversion. The same purchase on Wednesday does not. A Tuesday purchase preceded by a search-ad click counts as a click-through conversion instead, and the banner receives nothing.

Origin and evolution

Post-impression counting arrived with cookie-based third-party ad serving, which DoubleClick brought to market after its founding in February 1996. The concept gained a research base in late 2008. On November 17, 2008, comScore released norms compiled from nearly 200 brand studies, and on December 5 Fulgoni presented "How Online Advertising Works: Whither the Click?" at a Wharton conference. A European edition followed on March 11, 2010.

Google added view-through reporting for display advertisements on its Content Network on September 30, 2009, according to KoMarketing. On September 11, 2020, Google introduced engaged-view conversions, framing them as a stronger signal than credit awarded on an impression alone.

Privacy engineering then compressed the practice. According to Meta's developer blog, the company defaulted to seven-day click and one-day view from January 19, 2021, and said it would stop supporting 28-day click, 28-day view and 7-day view windows once Apple enforced its App Tracking Transparency prompt. That enforcement began on April 26, 2021, the same date SKAdNetwork version 2.2 added view-through attribution with a 24-hour limit.

Why it matters to marketers

View-through credit flows into return on ad spend (ROAS), cost per acquisition (CPA) and, increasingly, automated bidding. For buyers of prospecting display and online video, where clicks are scarce, it is often the only platform-reported evidence of a sales effect. When a platform changes the rules, reported performance moves without any change in actual sales. Meta's decision to remove the 7-day and 28-day view windows from its Ads Insights API took away reporting that many awareness campaigns had used to defend budgets.

Automation raises the stakes. According to Google, enabling view-through optimisation in Demand Gen moves those conversions into the Conversions column as biddable events, and the company warns that third-party systems will show a discrepancy because impression-based metrics are not exported. A figure once used to argue about value now steers spending.

Limitations and disputes

The central objection is causation. A view-through conversion shows that exposure preceded an action, not that it produced it. Google's own Demand Gen documentation concedes that its view-through optimisation does not directly target incrementality. Holdout studies exist to answer that question, and Meta's measurement framework ranks lift testing above attributed sales.

Inflation is the second. Practitioners in July 2025 named view-through credit among the main causes of inflated ROAS on Meta, and an agency chief executive launched a public apology campaign that November over similar overstatement. Cookie bombing means buying large volumes of cheap impressions so that converters are likely to have been exposed and the buyer can claim credit, according to ClickZ. A former agency executive told Digiday in 2022 that the practice remained widespread.

The research base is itself contested. In June 2012 Criteo published data finding that clickers were far more likely to buy, and Patrick Wyatt, its head of business intelligence, described the opposing view as "a common though misguided belief".

Coverage is a third weakness. According to Google, view-through conversions from browsers that block cross-site cookies cannot be reported at all.

Sources also disagree on specifics. Google's Demand Gen help page, as of September 2026, describes view-through optimisation as an open beta, off by default, covering images and video on YouTube. Reporting documentation surfaced on August 15, 2026, described by PPC Land, says optimisation will apply to video only and default to on for new campaigns. Both remain published.

Not the same as

View-through rate. The term has no settled meaning: Yahoo! JAPAN Ads uses it for full video completion, while much of the market uses it for post-impression conversion rates.

Engaged-view conversion. This requires a minimum watch time, such as 10 seconds on skippable in-stream in Google Ads. Meta renamed its equivalent to engage-through attribution in March 2026 and folded in shares and saves.

Lookback window. The window is the period during which credit can be claimed, not the conversion itself.

Viewability. A viewability standard measures the opportunity to see. It can act as a filter on view-through credit but measures delivery, not outcome.

Recent developments

Platforms moved in different directions through 2026. On January 1, Amazon applied shopping-signal enhanced attribution to view-based campaigns on its store inventory, keeping 14-day figures under "all views" metrics. Meta's window removal took effect on January 12. On August 11, Google Analytics replaced its fixed three-day engaged-view window with a range of 1 to 30 days.

OpenAI's path has been the most compressed. View-through reporting reached ChatGPT Ads on August 18 and 19, walled off from bidding, billing and CPA. In the same period, automated bidding became the default in new ad groups, optimising on a conversion count that excluded post-view credit. Two weeks later, an advertiser email described an impression-billed campaign type optimising through view-through conversions, with no launch date or window length disclosed as of September 2026.

Timeline

  • February 1996 - DoubleClick is founded, bringing cookie-based post-impression counting to third-party ad serving
  • November 17, 2008 - comScore releases Brand Metrix norms from nearly 200 studies on the view-through effect of online advertising
  • December 5, 2008 - Gian Fulgoni presents "How Online Advertising Works: Whither the Click?" at Wharton
  • September 30, 2009 - Google adds view-through conversion reporting for display ads on the Content Network
  • March 11, 2010 - comScore publishes a European edition of the Whither the Click research
  • June 27, 2012 - Criteo publishes research disputing the view that display clickers are an unattractive audience
  • January 1, 2019 - Amazon limits view-through credit to MRC-viewable impressions
  • September 11, 2020 - Google announces engaged-view conversions
  • January 19, 2021 - Meta defaults to seven-day click and one-day view attribution
  • April 26, 2021 - App Tracking Transparency enforcement begins; SKAdNetwork 2.2 adds view-through attribution
  • April 2022 - Google adds viewable-impression settings to Floodlight attribution models in DV360
  • October 16, 2025 - Meta announces removal of 7-day and 28-day view windows from the Ads Insights API
  • January 1, 2026 - Amazon applies shopping-signal enhanced attribution to view-based store campaigns
  • January 12, 2026 - Meta's view window removal takes effect
  • March 2026 - Meta splits attribution into click-through, engage-through and view-through
  • August 11, 2026 - Google Analytics makes the engaged-view conversion window editable from 1 to 30 days
  • August 15, 2026 - Reporting documentation on Demand Gen view-through optimisation surfaces
  • August 18-19, 2026 - ChatGPT Ads adds view-through conversions with a fixed one-day window
  • Week of August 31, 2026 - OpenAI signals an impression-billed campaign type optimising through view-through conversions

Summary

Who. Ad servers and platforms, including Google, Meta, Amazon, Apple and OpenAI, define and count view-through conversions. Advertisers and agencies configure the windows and rely on the figures to defend spend, while measurement specialists and practitioners dispute what those figures prove.

What. A view-through conversion is a conversion credited to an advertisement that was served but not clicked, provided the action occurs within a set window after the impression and no click or higher-ranked interaction claims it first.

When. Post-impression counting dates from cookie-based ad serving in the late 1990s. It gained a research case from comScore in 2008, reached Google's Content Network in September 2009, was compressed by privacy changes from January 2021, and was reworked by Amazon, Meta, Google and OpenAI during 2026.

Where. The mechanism runs inside ad servers such as CM360, inside walled-garden platforms including Google Ads, Meta Ads Manager, Amazon Ads and ChatGPT Ads, and on Apple devices through SKAdNetwork, across display, video, social and app inventory.

Why. Most display and video advertisements are never clicked, so click-only measurement records little of their possible effect. View-through counting fills that gap, at the cost of crediting exposure that may not have caused anything, which is why windows keep shrinking and lift testing keeps gaining ground.