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To date, there are two methods for generating a preview of an HTML email in the most popular email clients: live and emulated email tests. Here, we’ll go into the differences between live vs. emulated email testing and how each one impacts email rendering screenshots. Spoiler alert: Email on Acid exclusively uses live email testing.

Emulated Previews

There are two ways to emulate email testing. The first is with a simulator that email developers use to develop their applications locally. This negates the need for a physical device, such as a desktop or smart phone. The other emulating tactic mimics how a specific email client will render an email. Back in 2010 at the initial writing of this blog, Email on Acid was using this approach. Co-Founders John and Michelle were trying to figure out a way to programmatically emulate how emails would render on an email client. However, this approach gets hairy when browsers come into the mix. Reason being, it’s incredibly difficult to emulate each one like Internet Explorer, Firefox, etc.

By definition, emulated previews are not 100% accurate. At best, they are educated guesses as to how an email will render on a client and device.

To get around these issues, you have to go with what is real, and that is live email tests.

Live Previews

Live email testing guarantees complete accuracy and works by sending an email to an actual email client on a physical device. Today, Email on Acid operates solely on live email tests. We left the emulated tests back in our 2010 days where they belong.

How it works:

For every device that Email on Acid offers email previews on, we have those devices physically set up and running. When you run an email test, those devices receive the email on an open (live) email client, take a screenshot and send the preview back in your test results. Live email testing generates true-to-form previews that show the user exactly how their email will render. Due to their organic nature, live email tests can at times take up to a full minute or so to finish generating previews. It’s worth the wait though, since what you see is 100% accurate.

Why Accuracy Matters

The whole point of running an email test is to know what your subscribers are going to see before you hit send. Relying on anything less than a live email screenshot isn’t very helpful when you’re trying to make sure everything looks good.

How Do Other Platforms Run Email Tests?

There is no way for us to know how other email testing platforms run their email tests. We can’t speak to any service other than our own. That said, Email on Acid maintains an infrastructure such that we’re able to provide users with live email tests across 90+ clients and devices. This service comes with the assurance that email rendering screenshots will undoubtedly represent what subscribers will see. What makes Email on Acid different from other services, without knowing if they run live or emulated email previews? We are not just email previews. We are complete email content validation, from checking each email element to running a final test.

Always Run a Live Test

If you take away one thing in regards to live vs. emulated email testing, let it be this:

Live email testing is the only way to know for sure what your email will look like for subscribers.

Emulated email tests simply cannot promise such accuracy. An emulated preview is nothing more than an educated guess at how an email will render. Again, we can’t speak to any service but our own, but Email on Acid solely provides live email test results, because users deserve fully accurate email rendering screenshots. Every Email on Acid subscription comes with unlimited live email testing and Campaign Precheck. Take a seven-day free trial to give these tools a whirl on your next email. You'll see just how efficiently and effectively you can polish your email and prepare it for deployment. *Note: Get unlimited email previews when you start a free trial of Campaign Precheck.