The HTML Editor in OneSignal allows you to craft highly stylized, branded emails with complete control over layout and design for both desktop and mobile.

To make the most of HTML email design, we recommend:

  • Ensure you or a teammate has experience with writing responsive HTML emails that render well across different clients and devices.
  • Host all images in a publicly accessible location, such as your website, AWS, or other reliable hosting platforms.

Getting started

To begin creating your HTML email, select the HTML Editor option when setting up your message.

Image showing ability to select editing experience for email

Once selected, you’ll see a split-screen interface with the HTML code editor on the left and a live email preview on the right.

Using the HTML editor

Enter your HTML code in the left panel. You can use the Send Test Email feature to check how your email renders on mobile and desktop clients.

Image showing HTML editor beside the preview

Key features of the HTML editor

Click tracking

We automatically track clicks on links and CTAs within your HTML emails for performance insights.

An unsubscribe link is automatically included in the default HTML template. You can customize this link, but note that all emails are required to include one.

Learn more: Unsubscribe Links & Email Subscriptions

Import your own templates

Already have an HTML email template? Simply copy and paste it into the editor to get started.

HTML email best practices

Use inline CSS

Many email clients strip out embedded or external styles. Always inline your CSS to ensure consistent rendering.

Try this tool: Responsive Email CSS Inliner

Add alt tags to images

Alt text improves accessibility and ensures information is conveyed even if images are blocked or fail to load.

Email ClientBlocks Images?Shows Alt TextStyles Alt Text
AOLYesYesYes
GmailYesYesYes
YahooYesYesYes
OutlookSometimesYesYes

Source: Litmus Email Client Support

Name and format your HTML

Use semantic HTML and meaningful tag naming for accessibility. This helps screen readers interpret your content more accurately.

Also, use standard color formats and proper indentation for maintainability.

Broken links reduce deliverability and can flag your emails as spam. Test all links thoroughly before sending.

Avoid unsupported HTML

Most email clients do not support the following:

  • JavaScript or Flash
  • Embedded audio or video
  • HTML forms
  • Iframes
  • Text layering

Use hyperlinks to share additional content safely.


FAQ