When designing your email templates, you may see a message indicating that the template exceeds 100 KB. In this article, we'll explore what this actually means and how you can avoid it.
Implication of exceeding the limit
Once your email exceeds 100KB, it can negatively affect deliverability, as in some cases, this may cause the email to be marked as spam or lead to a poor recipient experience due to clipped content of the email.
It doesn't mean your email can't exceed this limit. Providers like Gmail may clip the message so the recipient has to expand it, while others might treat such emails as spam. Because it's impossible to predict how each provider will handle oversized emails, it's best practice to keep the message size within this limit to maintain deliverability and a positive recipient experience.
How can you influence the size of an email?
Optimal dimensions
Depending on your use case, your emails may require different dimensions. In general, keep in mind that very long emails that require extensive scrolling also increase the overall size of the message. Try to keep them to a reasonable length to provide the best recipient experience and keep the email size lower.
Complex and inefficient HTML, CSS
Using your own HTML and CSS is a great way to achieve your desired design without the limitations of pre‑made components. However, inefficient code, nested tables, wrappers, excessive inline styles, and unnecessary comments can all increase the overall size of the email.
When making your emails responsive, avoid duplicating sections or stacking content that only increases the size. Instead, follow responsive design best practices by using fluid layouts and media queries to adapt the same components across different screen sizes. Don't keep complete duplicate sections for mobile and desktop if a more straightforward responsive approach can handle both.
Use Visual Builder whenever possible
When your use case allows it, we recommend using the Visual builder over the HTML builder, as it generates more compact code and helps reduce the overall size of your emails. It can save you from potential issues and extra work when optimizing your campaigns in the future. This is especially important to keep in mind when working with Visual Builder, as similar problems often occur when you create separate blocks for mobile and desktop, which in the end increases the size.
Language versions in a single email
It's always better to create a language version of the email using the "Add language version" option than to add it within the same email as another component or HTML block, which would only increase the overall size of the email.
URLs and UTM parameters
Be mindful of the links you use in your emails. Keep them as short as possible to reduce overall email size; long URLs can quickly increase it. Wherever possible, reuse the same URL for repeated CTAs instead of generating new, slightly different ones. Avoid using a large number of unique links with very long UTM or custom parameters; keep parameter names and values concise and remove anything you don't actually need. Remember that custom campaign tracking fields and any additional tracking appended later can increase the final size of the email, especially if it contains many links.
Dynamic content
Try to avoid very long, personalized sections that repeat similar structures. If possible, display fewer products—for example, 3–4 instead of 8–10 or more—mainly when each item includes long titles, descriptions, or separate CTAs. These dynamic, personalized blocks should be used sparingly and optimized for size.
Custom CDN domain
If you want to save a few more KB in your emails, you can use a custom CDN domain. Each link increases the overall size of the email, and shortening links by using a custom CDN domain can significantly reduce the size of link-heavy emails.
Conclusion
Lightweight emails are easier to send, receive, and manage. Stick to under 100KB, and keep your communication fast and clean. Your recipients spend less time waiting for messages to load and more time focusing on what you actually want to say.