Posted 29th September 2011 | By Nick Evans, Chairman

Resizing images, is it necessary? I'm going to start by answering the question - Yes. A thousand times, Yes!

I've seen a lot of emails recently with images that have obviously been resized in the HTML editor rather than an image editor. I'm sure it looks great in their editor and it will probably look fine on most email clients too as a size has been defined. However images really should be saved as the size you want them to be in your email and then added to your html.

The reason? Well when you resize a 4096 x 3072 pixel image to 256 x 192 pixels, using your image editing software, it generally reduces the file size (unless you have done something horribly wrong). This is a good thing.

When you take the same 4096 x 3072 image and "resize" it in your HTML editor it does not actually resize the image. It takes the full size image of goodness knows how many megabytes and forces it to fit into the dimensions you specify in the code. This is a bad thing because the full image needs to be downloaded before the recipient's machine can make it fit into the dimensions.

When these huge images are downloaded it increases your server load (or your ESP's server load). I'll use a real-world example for this, the largest image file-size I have seen recently in an email (for a local delicatessen) was 5.6MB - I took that image and resized it to the dimensions required in the email and the file size was 30kb. Therefore the resized image could be downloaded 187 times, compared to 1 download of the original. I made a few more tweaks to the image compression and got the file size to 9kb (without any obvious loss of quality), meaning the file could be downloaded 622 times compared to 1 download of the original.

Can you see why it matters now?

The next issue is that it can take a long time to load on your recipients machine. When, what looks like a small image, takes a long time to download it feels as if your email is broken or your servers are slow. It's not a great user experience. Whilst resizing in the HTML editor may make things easier for you it means your customers get a rubbish experience.

Can you see why it's worth the extra time now?

What about people on their smartphone (or mobile internet)? Think about them the next time you want to resize in your html editor. That 5.6MB image mentioned earlier is enough to download a couple of MP3s or stream a youtube video. Very few smartphone contracts now have 'unlimited' data and if they do there is usually a fair usage cap - imagine how annoyed your customers could be when they open up one of your emails and the 4 or 5 images you couldn't be bothered to resize suck up 20-25mb of their allowance.

Can you see why its important to resize your images externally now?

Then there is the potential that it may harm your deliverability. Some spam filters will detect that you are using a large image file and decide that you are untrustworthy, because in the past spammers have used large images to avoid spam filters. This means your mail could end up in the spam folder rather than the inbox simply because you didnt resize your images.

Can you see that resizing your images can destroy a good email campaign now?

So are you still too lazy to resize your images externally rather than in the html editor, knowing it increases your server load, makes your email look broken, offers a dreadful recipient experience and could potentially harm your deliverability?

Dont have an image editor on your machine? Or worried that it will cost too much to get one? Well there are lots of free downloadable alternatives varying in complexity. I would recommend Aviary which is an online image editor that can resize images amongst many other things.

Obviously at ExtraMile Communications we resize all images using an image editor before using them in an email for any client.

As a final example, today a global company of experts in email deliverability used by global brands - we hesitate to name them as they are much bigger than us! - sent an email with an image that was 2.6mb. We took the image and resized it to the size it was in the email, making it 37kb. We then tweaked the compression slightly and reduced the file size to 8kb with no discernible loss of quality, a reduction in file size of 99.7%

So even the experts get it wrong occasionally.

Rant over!


Ean from ExtraMile Communications Ltd in Eccleshall, Staffordshire.

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