Why a few kilobytes can hide half your campaign
Gmail clipping is the most visible consequence. Everything after the cut — often the footer, the unsubscribe link, sometimes a CTA — disappears behind a link most recipients never click.
Weight also acts before and after delivery. Very heavy campaigns can be slower to process at send time, and heavy resources slow rendering on mobile, where a delayed hero image is often the difference between a read and a swipe.
A clipped email is a partially delivered email.
The weight limits that matter
Two different measures, two different problems. HTML weight decides whether Gmail clips your email. Total weight — HTML plus every image, font and GIF downloaded when the email is opened — decides how fast it loads.
How to read an email weight check
A complete check looks at three things: HTML weight (the clipping factor), total resource weight (the loading factor), and the list of referenced domains (the reliability factor).
5 best practices
- Keep HTML under 100 KB: clean up unused styles, duplicated blocks and editor-generated code.
- Compress every image (a tool like Squoosh works well) and export it at its actual display size.
- Prefer light formats — JPG for photos, PNG only when transparency is needed — and use animated GIFs sparingly.
- Host assets on a reliable, fast CDN and avoid unnecessary third-party calls.
- Keep total weight under 500 KB so the email stays smooth even on slow networks.
Common mistakes
- Measuring the exported HTML file instead of the email actually sent: link tracking and platform code add weight after export.
- Duplicating desktop and mobile versions of the same blocks in responsive templates, which can nearly double the HTML.
- Pasting content from a word processor or design tool, which brings hidden markup and inline styles.
- Placing a heavy animated GIF in the first screen, delaying the one area that matters most.
- Forgetting the tracking pixel, often placed at the end of the HTML: when an email is clipped, the open may not be recorded.
How Inbox Maestro checks it
Inbox Maestro weighs the test email your platform actually sends — after tracking and platform code are added — and measures its exact HTML weight, its clipping risk and its total weight, including every image and resource downloaded when the email is opened. It also lists every referenced resource and domain, so you know where the kilobytes go. The result appears in the Checkup section of your report, under Composition.
Action: → Drastically reduce the weight of external resources: aim for a size under 500 KB and never exceed 2,000 KB. Prioritize image optimization.
Frequently asked questions
Why does Gmail clip emails?
Gmail truncates messages whose HTML exceeds roughly 102 KB, showing “View entire message” instead of the full content. The limit applies to the HTML code, not to the images.
What is a good size for a marketing email?
Aim for HTML under 100 KB and a total weight (HTML plus images and other resources) under 500 KB, for smooth loading even on slow connections.
Do images count toward Gmail clipping?
No. Clipping is triggered by HTML size alone. Images affect loading speed and total weight, which are separate — and equally real — issues.
Why is total weight higher than the message size shown in my email platform?
Because the message size usually covers only the email itself: its HTML and text. Images, GIFs and fonts are hosted separately and downloaded when the recipient opens the email. Total weight adds them up, so it reflects what a phone actually has to load — and that is what decides how fast your campaign appears.
Does email weight affect deliverability?
Indirectly. Very heavy campaigns can be slower to process, and slow-loading emails degrade engagement — which mailbox providers take into account over time.