Definition
Email weight is the total size of an email file, measured in kilobytes (KB) or megabytes (MB). It includes the HTML code, embedded or inline CSS, images hosted externally or embedded, and any other assets. Email weight directly affects load time, user experience, and deliverability.
Gmail clips emails that exceed 102KB, replacing the bottom of the email with a "message clipped" link that reduces visibility and engagement. Mailbox providers also consider file size as a deliverability signal. Keeping email weight low is a standard optimisation practice.
Email Weight Guidelines
| Email Weight | Impact |
|---|---|
| Under 50KB | Excellent — fast loading, no clipping risk |
| 50–100KB | Good — standard optimisation target |
| 100–102KB | Risk — Gmail clipping threshold |
| 102KB+ | Gmail clips the email, reducing engagement |
| 200KB+ | Slow loading, potential deliverability issues |
Best Practices
- Keep total email weight under 100KB to avoid Gmail clipping
- Optimise images — use JPEG at 60–80% quality, PNG for simple graphics
- Host images externally rather than embedding them as attachments
- Minify HTML and CSS to reduce code weight
- Limit the number of images to 3–5 per email
- Use web-safe fonts instead of importing large web-font files
- Remove unused CSS and redundant code from email templates
- Test email weight before every send using testing tools
Related Glossary Terms
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Email Analytics
The measurement, collection, analysis, and reporting of email performance data to understand subscriber behaviour and optimise campaign results.
Email Marketing Best Practices
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Email Campaign Optimisation
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Mobile Conversion
Mobile conversion optimises email campaigns for subscribers reading on smartphones and tablets, ensuring a seamless path from email open to desired action on mobile devices.
Multivariate Testing
Multivariate testing (MVT) tests multiple variables simultaneously to identify the optimal combination of email elements for maximum engagement or conversion.
Frequently Asked Questions
Yes, but differently depending on how images are hosted. Externally hosted images (linked via URL) do not count toward the email's HTML file size but affect overall load time. Embedded images (base64 or as attachments) significantly increase email weight and should be avoided for all but the smallest graphics.
Most email testing tools (Email on Acid, Litmus, Mailgun Inspect) display email weight. You can also check by viewing the email's source or using browser developer tools. Some ESPs display email weight in the campaign editor or pre-send checklist.