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Image loading speed, a key factor for user experience

Category: Features

Imagen Image loading speed, a key factor for user experi

Internet connections are getting faster and faster, even on mobile devices. Everything seems to be moving fast and no one wants to waste an extra second waiting to see the image of a newsletter. This can be negative for the sender and can be avoided by optimising the weight of the campaign to ensure that it loads faster.

To calculate how much a message weights, two elements are taken into account:

  • HTML, i.e. the code it is written in. If it is not clean, has strange scripts or is too large (it should not exceed 102kb), it affects deliverability and may be considered spam or worse cut.
  • The size of the images that had to be downloaded, either when opening the email or when the user activates this option in their email manager. Remember that email marketing does not send any attachments or embedded files, but links to external webpages.

Indeed you have received an email in which you have had to wait a long time to see it fully loaded. It seemed like forever, although it probably took only a few seconds to charge. This perception of slowness is a mistake you can't afford to make because, if the user loses interest, the click-through rate will drop and they won't complete the action you were expecting them to do.

The weight of the images affects the user experience and the results of your campaigns, as well as impacting your reputation by giving the impression that you have poorly designed your message. You can minimise waiting time by optimising image load times, or in other words, how long images take to download.


How do you calculate image load times?

Our campaign editor does it for you, so just click on the rocket icon in the preview menu. You will then be able to see the message size in kb and calculate the loading time of all your images according to the different connection types.



This chart will be handy for you because:

  • It warns you if any image is broken (it will be identified in the status column).
  • It shows you the individual size of each image, so you can identify at a glance which one is slowing down the charging time and try to optimise it.
  • Calculates in milliseconds the charging time of the entire number of images according to the chosen speed.

In the info dialogue at the top, you will see our recommendation in red if the loading time is too high or in blue if the loading time is optimal. 


The following table gives you an overview of the recommended loading time for each type of internet connection:


By default, in the editor preview you will see the calculation taking into account the loading speed when viewing the inbox from a desktop computer, but you can change the broadband in the drop-down menu:


How to optimise images for a newsletter?

Not all the images in the mailing can be optimised the same way, for example, the header is usually smaller (in kb) than the product photos. In general, we recommend that you look at the following:

  • The size: they don't need to be wider than 580px.
  • The resolution: 72 dpi is usual, do not use images with printing resolution (300 dpi) because they do not look better on screen.
  • The extension: avoid BMPs, if possible use JPG or GIF extensions.
  • The maximum weight of each image should not exceed 100kb. Actually, our editor will allow you to upload up to 200kb images because, when you upload it, we will automatically optimise it to reduce its weight. If this is not possible, you will see a warning and you will have to do it on your own with an image optimisation tool.


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