Litmus Behind the Scenes: How We Improved Testing Through Hundreds of Mac Minis

[ 0 By

One of our main goals on the development team here at Litmus is to build a reliable, accurate testing infrastructure for our users. Our tools enable our users to test emails across over 30 clients, browsers, and devices in minutes—without having to purchase, set up, and maintain all of those environments on their own.

Our users put their emails and trust in our hands—which is a big deal to us! Not only do we want to provide accurate, actual screenshots (not emulations!), but we want to do it quickly and reliably. As a result, we’re constantly looking for new ways to make our solutions faster and more dependable. Since we’re frequently asked about how Litmus works behind the scenes, we thought we’d give you a peek behind the curtain.


Last year, we began to experiment with ways to speed up our testing time. We discovered that the major delays were occurring during the previewing process, in which the servers had to load the email in an actual email client, resize it, and then take a screenshot. These delays made sense: the majority of our servers are hosted on Amazon’s EC2 service, which allows us to easily scale as more people use Litmus, but those servers are optimized for tasks like handling web requests or transforming data sets—not for rendering user interfaces.

We set out to solve this problem by finding machines that more closely resemble traditional desktops and laptops. We had some Mac minis around the office for iOS testing, so we loaded Windows on one of them and ran some previews tests on it. The results were amazing!


Litmus Mac minis @ MacStadium in Atlanta, GA

By moving our testing machines to Mac minis, the average time to complete a full previews test went from 32 seconds to 21 seconds. This not only saves our users time, but it cuts down on the number of machines we need to handle the testing load. Interactive Previews also experienced a similar evolution; not only opening your email faster, but springing to life when you scroll up and down within your browser.

To top it off, Mac minis are amazing pieces of hardware, and you can fit a lot of them in a small space. Our partners at MacStadium have provided us with world-class hosting and redundancy on our data and power connections, and their relationship with Apple provides us with machines whenever we need them. As a result, we’re able to scale whenever necessary.

But don’t worry—we’re not done yet! We’re always looking for new and innovative ways to improve our testing speeds and reliability. Stay tuned for exciting product updates in the near future.


Have any questions for us? Feel free to drop us a line at


Not a Litmus user? Try us free for 7-days and see us in action! All free trials include access to our previews, interactive testing, analytics, and spam filter testing tools.

Access your free trial →