In early December 2013, Gmail started caching images for users accessing Gmail via the webmail interface and the mobile Gmail app. When an image is cached, it is downloaded from the original server and stored on a proxy server. Subsequent views of the cached image will always display from the proxy server rather than the original server.

According to the Gmail team, this change keeps emails secure by checking images for known viruses or malware. While safer emails are wonderful for Gmail users, Google’s new image caching poses a few challenges for tracking email open data in the interface and Gmail mobile apps:

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. The silver lining is that open rates for the native email client on Android—which has support for responsive emails—are now more accurate.

Another effect of image caching that some Gmail subscribers have noticed lower quality images in their emails due to compression artifacts from the caching process.

Above is an example of failed image caching in an email.

Unfortunately, some users have even noticed images failing to render at all. Others have reported images loading in the wrong placeholder!


Don’t fret! Use individual tracking with Email Analytics to track emails—even in environments where Gmail caches images. While geolocation and some device tracking data is no longer detectable, keep in mind that Gmail accounts for 12% of total opens and only about 20% of those opens occur in the webmail interface.

What should you do?

As stated above, if you’re using Email Analytics, be sure to use individual tracking so you can properly track opens. With device tracking information no longer available for Gmail users, it’s essential to test your emails before sending to be sure they look great in all environments.

If you previously used geolocation data for targeted emails, you’ll have to try a different strategy for Gmail users. Perhaps consider having users update their location in your subscription center.

When it comes to degraded images, images not loading at all, or images loading in the wrong place, there is currently no solution. As a result, now more than ever, it’s important to design your emails for images-off optimization—use ALT text, background colors, and lots of live text—making sure your emails can be understood and enjoyed even if images are not present.