Gmail Continues to Shift the Market Share Landscape

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The effects of Gmail image caching continue to impact market share stats. Four months after the initial roll-out of image caching and automatic image downloads, Gmail opens are starting to even out. We saw another percentage point increase this month, bringing Gmail to 11% of total opens—a 285% increase since December.


Mobile Gmail apps for both Android and iOS download images automatically and serve them via Google’s caching service. As users update to the new mobile Gmail apps, we’re seeing image caching affect mobile open rates, specifically opens made with the Gmail app on Android. As Gmail open rates rise, there has been a corresponding drop in Android opens. Since January, Android opens have dropped 34%—now representing 8% of opens.



When Gmail automatically downloads and caches images, those cached images—including open tracker pixels—are stored on Gmail’s servers. Gmail then loads the same images from the same servers for everyone—regardless of whether they open using Gmail in a web browser or a Gmail Android or iPhone app.


As a result, Gmail opens made in a browser and on mobile Gmail apps look the same—there’s no way to distinguish webmail from mobile. While automatic image downloads mean more accurate open rates and a better subscriber experience, image caching eliminates the ability to determine the user’s device. To be clear, this only affects opens that occur in Gmail, either in a web browser or in a Gmail mobile app. Emails sent to Gmail accounts but opened in other mail apps are not affected. The silver lining is that open rates for the native email client on Android—which has support for responsive emails—are now more accurate.


Looking at recent changes to the top 10, Apple Mail took back its #5 spot and bumped Android down to #6—not surprising given the dip in Android opens.

After hitting 51% in November and December, mobile opens appear to have been on a continuous decline. Thanks to image caching, what appears to be a mobile loss can be partially attributed to Gmail opens—reported as an increase in webmail opens. Detectable mobile opens now represents 47% of total opens, whereas webmail opens are at 25%.


Desktop opens also increased 1 percentage point to reach 28% of opens. This rise can mostly be attributed to Outlook, which claims 14% of opens. It’s still holding steady at the #2 spot!

As always, keep in mind that some email clients may be over- or under-reported due to automatic enablement of images and/or image blocking. Tracking trends over time is the best way to monitor open data for email!