Keep your email’s HTML under about 102KB. Go over that and Gmail cuts it off, showing a “[Message clipped] View entire message” link instead of the rest.

That’s the short answer. The rest is worth knowing too.

The limit isn’t official

Google doesn’t publish it. 102KB is the number the email industry works to, and Al Iverson’s testing at Spam Resource found the real cutoff sits a little above that. So 102KB gives you a sensible margin rather than being an exact line.

What counts towards it

Only the HTML of the email. Images load from a server, so their file size doesn’t count, however big they are.

What does add up:

  • heavy template code, especially from drag-and-drop builders
  • the same inline styles repeated on every element
  • long tracking URLs, since your ESP rewrites every link
  • extra code your ESP adds, which you won’t see in your editor

Long issues built in heavy templates are the usual culprit. Digest-style newsletters with dozens of stories are particularly prone to it.

What clipping costs you

It’s more than a tidiness problem. Everything below the cut stays hidden until someone taps through, which usually includes:

  • your unsubscribe link and postal address, which CAN-SPAM and other laws require you to show
  • your last few stories or a sponsor placed near the bottom
  • the open-tracking pixel, if your ESP puts it at the end of the email, which means a clipped email may not register an open at all

A missing unsubscribe link also makes the spam button the easiest way out, which you don’t want.

How to stay under it

Check the HTML size before you send. Many ESPs show it, and email testing tools will too. If you’re close to the limit:

  • trim the template’s code, or switch to a leaner one
  • cut down repeated inline styles
  • shorten the issue, or link out to the full version of long sections
  • send a test to a Gmail account and scroll to the bottom

If your template is regularly near the limit, it’s worth fixing properly, because newsletters tend to get longer over time, not shorter.

References

  1. [1] testing at Spam Resource — spamresource.com