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Everything You Need to Know About Gmail Rendering: Webinar Recording


Gmail is a headache for people who make and send email. Until September 2016, Gmail required the use of inlined CSS and didn’t support responsive email. A major update to the Gmail rendering engine rolled out support for embedded styles and media queries. However, post-update there still remains a lot of rendering fragmentation, causing a lot of confusion in the email community.

In this webinar, Product Manager and resident email hacker Kevin Mandeville provides a detailed walk through Gmail rendering, covering key aspects of the update.

Didn’t make the webinar? That’s ok. We recorded the whole thing. Watch the recording above and download the slides below:


We didn’t have time to get to all of the questions during the webinar, but we’ve answered them here on our blog. Have any additional questions? Leave them in the comments, we’d love to answer them for you.

Q: Does Inbox by Gmail use the same rendering email as the Gmail app?

A: If you are comparing the Gmail app and Inbox by Gmail app, they inherently use the same rendering engine. There are a couple of differences such as the <section> tag not being supported in Inbox by Gmail, but they are very minor. The only key difference is that POP/IMAP accounts on the Gmail Android app do not have embedded CSS support.

Q: Are Gmail business accounts considered POP/IMAP accounts?

A: No, they are not. G Suite (formerly known as Google Apps) are accounts created in Gmail, so those are Gmail accounts that live in the Gmail ecosystem. Those are not POP or IMAP accounts because they are not emails living on an external third party provider’s service. Since these live on Gmail servers, they have the rendering update and support embedded CSS and media queries.

Q: In the email client market share tracker, is there any way to know what the Gmail app market share is, separate from the general Gmail?

A: One of the limitations when it comes to Gmail tracking is differentiating between webmail and mobile opens. Because Gmail started image caching several years ago, it affects our ability to properly segment the difference between mobile and webmail opens on gmail. Those opens get counted essentially as the same. You can learn about how we’re able to segment Gmail opens here. We also just started tracking the Samsung email app independently from Android in order to differentiate.

Q: On the Inbox by Gmail slide there is a “u,” what does that “u” stand for?

A: In Gmail, before the email body starts, it prefixes the HTML with a blank underline tag <u></u>. You can target the “u” in CSS for Gmail clients.

Q: Does the white space no-wrap with spaces hack for IMAP cause a spam trigger?

A: No, it wouldn’t. The notion that spam is heavily relied on for content is a bit of a myth, and that hack would not trigger spam filters at all. Spam is built more off your reputation, sending activity, and engagement, such as whether people are marking you as spam.

Q: Can Gmail support box shadow?

A: According to Gmail’s documentation, Gmail does not support the box-shadow property.

Q: Does Gmail support !important rules in CSS?

A: Yes, Gmail supports !important values in CSS.

Q: Did Google ever give any justification for the removal of checkbox selector support?

A: No, they didn’t state anything publicly. But, based off personal knowledge on Gmail’s approach to the product, security and privacy drives many of their product decisions. Interactivity in email, in their eyes, is potentially harmful for security purposes. They don’t want to enable a functionality that could be used to trick people or be used for fraud.

Q: When I forward an email in Gmail, I lose my <style> blocks. Have you experienced this?

A: Yes, Gmail removes any <style> blocks when forwarded. If forwarding is a big concern for your email rendering, you should consider sticking to inlining CSS to avoid this. However, we recommend viewing your Email Analytics to see if you have prevalent forwarding behavior in your audience.

Q: If you place any pixels in the footer of your email and it gets clipped, are they recognized?

A: No, any content that gets clipped by Gmail if it exceeds the 102KB HTML file size limit will not load, thus preventing tracking pixels from firing if placed below the clipping line.

Q: How do you check your HTML file size?

A: You can easily view the file size of your HTML email by looking at the file detail information locally on your machine in Finder (Mac) or Explorer (Windows). We also put together a guide on everything you need to know about file size if you’d like to learn more.

Q: Any idea why Gmail doesn’t support Google Fonts? Any idea of when will they support them?

A: We aren’t sure why Gmail doesn’t support web fonts of any kind – even Google Fonts. Since they now support embedded CSS and media queries, web fonts shouldn’t be any more of a security issue. We hope this changes in the future and Gmail decides to support them!

Q: What is the definition of “Gmailify?”

A: Users can “Gmailify” their email address to get all the features of Gmail. You can learn more about it and how to do it yourself on Google’s blog.

Q: Why would someone use the Gmail app if they don’t have a Gmail address?

A: There are many reasons – mostly UX and security – that come down to a user preference of wanting to switch email apps without losing their email address. Think of it like switching a phone provider and mobile device, but still being able to keep your phone number. It all depends what a user values most.

Are your subscribers opening in Gmail?

Gmail can be super confusing, even with the rendering update. Know whether or not it’s worth the effort by using Litmus Email Analytics. Learn about more than opens and clicks—see geolocation, email client, engagement, and more.

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