What’s the maximum file size for an HTML email?

A few weeks ago, one of our customers wrote in to ask what the maximum file size is for an HTML email. Keeping in mind how expensive data can be on mobile devices, the obvious response would be, “as small as possible”. But for a moment, we took pause to wonder - is there really a set limit, after which email clients simply spit the dummy?

Thanks to Michelle Klann at Email on Acid, we’ve got an answer - 102kb. In a recent blog post on email size, she explains:

‘If your email exceeds 102K, Gmail will display the first 102K and then it will clip off the remainder with a few different variations depending on the device.’

Listed are the consequences for exceeding this limit in Gmail, the worst case being:

“(after reaching 102k) the mobile version of Gmail for the iPad does not appear to offer any links for viewing the entire message, instead the email is simply cut off.”

Thankfully, images do not count towards this total - just the initially-downloaded HTML content. Of course, an email would have to be pretty long (or code heavy) to clock in at 102kb - which is a usability challenge in itself.

The bottom line is that if your HTML file size is nearing 102kb, your email is too long. Think about how to better refine the email message and/or placing your content on a landing page for easy reading in the browser instead.

Posted by Ros Hodgekiss

10 Comments

  • Steve Martin
    22nd November

    Thank you for this article. I immediately was interested what answer you would come up with.

    Now I have read through it, I wonder why Gmail should be the measure of all things. Google isn’t the ultima ratio for search engines, so why should it be for email? If you look at Thunderbird’s settings for instance, the ‘Do not download messages locally that are larger than __ KB’ has a default value of 50 KB! So if one checks this box without changing the default setting, the answer to the question stressed in the subject would be ‘50 KB’.

    IMHO the ultimate response to the question should be your initial idea: ‘as small as possible’.

  • Ros Hodgekiss
    22nd November

    Hey Steve, that’s a great observation - thanks for letting us know about the default in Thunderbird. Agree that Gmail is by no means the bar when it comes to email, however it’s one of the few email clients that we’ve come across that has a definitive limit.

    I’d absolutely love to know if anyone else has hit kb limits on email clients - if you have, be sure to post a comment.

  • Steve Martin
    22nd November

    Hey Ros, you made a point with the definite limit in Gmail. That’s adding to a longer list of things why one shouldn’t use Gmail I suppose ;)

    Re the TB setting, I found it particularly useful when travelling with the MacBook and checking emails via tethering on a data roaming connection for which high fees apply. So the mobile scenario you mentioned in your initial post definitely holds.

  • Viktor Dite
    23rd November

    >>Thankfully, images do not count towards this total - just the initially-downloaded HTML content.

    if images are not involved in the total, what does this article told us? nothing, i guess. 102kB of pure HTML is so much code, you’ll even not use it on a webpage. why? Googles Bots do only read the first 100kB….

  • Fionnuala McIvor
    23rd November

    Hi Viktor, obviously it depends on the design of your email template, but if there’s more than one column in the layout then your code can bulk up very quickly. Building a pure HTML email correctly with nested tables and CSS included inline (as required by most email clients) along with all the other tricks of the trade, it becomes very easy to reach 100kb of code.

    We’ve also come across this problem in Yahoo Mail (UK) when the code is around 100kb, similar to Gmail in which a message appears and the user must click a button to view the rest of the email. One solution is to remove all the ‘tabbed’ parts of the nested code, which can take the overall HTML file size down enough to meet the cut-off point, but on the downside, it makes the code a little harder to read and amend further down the line.

  • Elliot Ross
    23rd November

    one further thing to watch out for is that by the time your code has been through an email sender, extra code will have been added. It depends on the platform and each build, but common things include links being encoded and tracking information being added - this all adds code, so it’s worth aiming for a lower limit to allow for this.

  • Remy Bergsma
    24th November

    One tip for CSS: when u put the CSS in a style tag in the head tag, put all CSS per class and element on one row. It can shave off some data in the long run, depending on the total amount of CSS lines.

  • Andrew Smith
    30th November

    We proved over multiple split tests that shorter mails had a better open rate (statistically significant - 32% compared to 27% for longer mails). I can only guess certain mail servers spam longer mails more frequently.

    Anyone had any experience of this?

  • Ros Hodgekiss
    30th November

    @Andrew Smith - That’s a great observation there, it could also have something to do with clarity of the message/Call To Action, too. Although this is a pretty un-scientific observation, I’ve generally seen that email campaigns that cut back on the filler text tend to have stronger CTAs and are more easily scannable. Love to hear everyone else’s thoughts on this, too :)

  • Ryan E.
    15th December

    Excellent article, I had an issue back in October with a newsletter that was an internal email for my client. It had a lot of info to pass on to the company. I spent hours trying to figure out why my email was getting cutoff, in the end I had to use images for some of the stories, which I despise if not necessary.
    I just went back to the file and noticed it was 64k and the text file was 15k, that’s still under the specified amount. So, I went to the email in my Gmail account and exported the code base which included HTML, text, and some bits of ISP info and it came in at 115k.
    Thanks for the info again!

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