Does the size of email images affect open rate or click-through?

  • 15 March 2021
  • 4 replies

Userlevel 1
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Has anyone noticed a difference in email open rate or click-through rate if the email contains large images so that the total email is 500 KB, 1 MB, even 1.5 MB?

The reason is that we could work faster if we could upload to Klaviyo our full images and not have to worry about tweaking their dimensions, quality and format to get them as small as possible (as we do on our website).

For example one image might be a PNG that is 417 KB but if we optimized it we could make it a JPG at 84 KB.

Is that worth the effort?



Best answer by David To 16 April 2021, 22:21

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Userlevel 6
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Hi Scott @ScottCodes

This is a great question! I cant speak from experience on whether or not I have personally noticed any differences in email OR/CTR (perhaps others in the Community can weigh in on this!) - but I do know that the image size of a graphic does not impact the size of an email, since images are loaded from an external source (e.g., your Klaviyo image library). With that being said, I don’t see the benefit of trying to optimize the graphic size. The exception is whether you use a GIF, which counts each frame as an individual image to load. More details on that in this article. There’s also a post in the forum re: best image resolutions that might be helpful for additional context: 



Userlevel 1
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Thanks for the reply.  I’m not sure I understand.  It sounds like you’re saying that an image in our Klaviyo library of say 1MB will not load any slower in the email browser than if we compressed it to say 100 KB.  How does that work?  

Userlevel 6
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Hi @ScottCodes

Ah, my apologies - I think I misunderstood your original question. The image size of a graphic does not impact the size of an email, but that doesn’t mean that the size of the image does not impact the load speed. There’s another post in the Community where @mkprkr and I address how the load time and image size are correlated. Per the details below, I was wrong to say that you shouldn’t try to optimize the size of your image to increase load speed.


Here’s the answer I shared, for easy accessibility: 

It sounds like currently, the emails you are sending with Klaviyo take a long time to load images, and you’d like to know what the reason could be?

As @mkprkr points out, generally the images you see in an email are actually links to an external URL where the images are located. When an email is sent out through Klaviyo, the browser is the one who loads the images; Klaviyo only sends the location of the image via the URL. Therefore, if you have detected that the images are loading slower, it is highly unlikely that the source of the problem is Klaviyo.

To add to this, some ways to mitigate this could be to reduce the size of your image (but don’t reduce it so much that it loses the quality!). In this blog post on 5 Rules for Using Images in Your Email Templates, it’s highlighted that: 

the larger your images are, the longer they’re going to take email clients to load. A long load time can be the difference between someone reading or ignoring your email. People are impatient — Kissmetrics reports that 40% of web visitors will abandon a page if it takes more than 3 seconds to load, and the same is true of email load times.

To make sure your emails don’t load too slowly, test them using a service like Litmus’s Image Check.

In fact, you can even resize an image directly in the Image Block editor. More details and tutorials on that here. 

Userlevel 7
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Hello @ScottCodes,

Elaborating further on what @cassy.lee has mentioned. We would highly encourage optimizing your images for better load times within the emails to encourage users to immediately see the content of your emails and have the elements be available to be clicked on.

However, you may still be seeing less than desirable open rates for emails that have an overall size greater than 102KB due to clipping. 


Although images are not counted towards your overall email size when sent, should your email size be greater than 102KB, it would impact the open rates of your emails from your Gmail users. This is because when an email is clipped, the tracking pixel Klaviyo uses; which is housed at the bottom of your emails is omitted and therefore not tracking these “opens”. 

Through a combination of having larger images causing the content of your email to be delayed in loading and the email being clipped due to surpassing this 102KB limit may lead to less than anticipated open and click rates. For best practices to alleviate clipping in your emails, you can reference our Why Is My Email Being Clipped? article.