Digital sustainability is often treated as something complex. It gets tied to infrastructure decisions, cloud providers, or large transformation programmes. In reality, a lot of digital emissions come from everyday decisions that are made without much thought.
Every time a website loads, data is transferred. That data needs energy to move through networks, power servers, and render on devices. On its own, each interaction is small. At scale, it adds up quickly.
One of the most consistent contributors to this is image usage.
Why images matter more than you think
Images are a core part of how websites work. They help explain things, improve engagement, and make content easier to process. They also make up the majority of a page’s weight.
The size of the average webpage as of 2024 was around 2.4 MB, and images typically account for 50 to 60% of that. That means more than half of the data being transferred on each page load is visual content. From a sustainability point of view, that matters.
More data means more energy. And when that data is being transferred thousands or millions of times, small inefficiencies become a real issue.
The relationship between data and emissions
There is a direct link between how much data is transferred and the emissions created.
According to a study by the International Energy Agency (IEA), the internet accounts for around 1% of global electricity demand. That translates into around 300 million tons of CO2 annually equivalent to the carbon footprint of the aviation industry.
Estimates suggest that transferring 1 GB of data can result in around 3 kg of CO2 emissions. The exact figure varies depending on infrastructure and energy sources, but the direction is consistent. More data leads to more impact. More images leads to more data.
Where inefficiency tends to come from
Most organisations are not intentionally creating inefficient websites. It usually comes down to a lack of visibility and process.
Common issues include:
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Uploading images far larger than they are ever displayed
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Using file formats without thinking about efficiency
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Adding decorative images that do not add any real value
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Serving the same large assets to every device
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Repeatedly loading images that could be cached
None of these decisions look like a problem in isolation. Together, they create a constant flow of unnecessary data.
Practical ways to reduce image-related impact
You don’t need to sacrifice quality to reduce file sizes. It is more about being deliberate.
1. Use the right format for the job
Different formats behave differently.
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JPEG works well for photography where some compression is acceptable
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PNG should be used when transparency or sharp detail is needed, but not by default
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WebP and similar formats can reduce file sizes significantly, by up to 30%, without noticeable quality loss
Choosing the right format upfront avoids carrying unnecessary weight.
2. Resize images to match how they are used
A common issue is uploading images that are much larger than they need to be. If an image is displayed at 800 pixels wide, there is no benefit in uploading a version that is 3000 pixels wide. It just increases the amount of data being transferred.
3. Compress images properly
Most images can be reduced in size without any visible difference.
Tools like TinyPNG or ImageOptim remove unnecessary data from files. This is one of the simplest changes to make and usually delivers immediate results.
4. Serve different images to different devices
Not every user needs the same file.
Using responsive image techniques allows smaller images to be served to mobile devices, rather than forcing them to download large desktop versions.
5. Avoid loading everything at once
Lazy loading means images are only downloaded when they are needed.
For pages with a lot of content, this reduces the amount of data transferred upfront and improves performance at the same time.
6. Cache images effectively
If someone visits your site more than once, they should not need to download the same images again.
Caching reduces repeated data transfer and makes returning visits more efficient.
What small changes look like in practice
In isolation, reducing image sizes looks like a small step, but the overall impact can be huge. On a website that receives thousands of visitors daily, optimising images can save gigabytes of data transfer every month, which in turn reduces CO2 emissions.
For example, if a website reduces the file size of a single image by just 50 KB and that image is loaded 10,000 times a day, this equates to a daily saving of 500 MB of data. Over a year, this could prevent the emission of approximately 180 kg of CO2. If you were to offset this figure, you would need to plant several trees. As usual, prevention is the best cure.
The bigger opportunity is removing what is not needed
Optimisation helps, but it only takes you so far. The bigger gains usually come from stepping back and asking a more uncomfortable question: should this image exist at all?
A lot of websites are carrying visual elements that don’t really do anything. Background textures, decorative icons, repeated imagery across pages, stock photos that don’t add meaning.
From experience, this tends to happen early in the process. Designs are created to look complete and visually engaging, often in ideal conditions with no constraints. Then those designs get built as-is. At that point, removing anything can feel like going backwards, so everything stays.
From my earlier experience working at a branding agency, I’ve worked on plenty of sites where we added images simply because the layout felt empty without them. Not because they improved understanding, not because users needed them, but because it felt like something should be there. Once those decisions are baked into templates and rolled out across dozens of pages, they become much harder to challenge.
The result is a site that looks polished, but carries a lot of unnecessary weight.
Why this matters for organisations
For smaller businesses, this is usually about performance and cost.
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Faster websites
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Lower hosting and bandwidth usage
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Better user experience
For larger organisations, it becomes a scaling issue.
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Reducing unnecessary data across large digital estates
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Setting standards for teams to follow
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Supporting wider sustainability goals
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Avoiding inefficiencies that compound over time
The underlying principle is the same. Reduce what is not needed, and improve what remains.
A more sustainable web comes from better decisions
There is often an expectation that digital sustainability requires a big change. A new platform, a different provider, or a major overhaul. In most cases, this changes are not where the real impact comes from.
Real impact comes from the smaller decisions that we make every day. What gets added to a page, what gets left in place, and what gets reviewed or ignored over time. These decisions tend to build up in one direction. More content, more assets, more data. That’s how websites become inefficient.
A more sustainable approach is about being more deliberate. Not just adding by default, but questioning whether something is needed in the first place. Image optimisation is a good example of this. It is simple to implement, easy to measure, and often highlights wider inefficiencies in how digital content is managed. When that same thinking is applied across content, design, and development, the overall impact becomes much more noticeable.
Where to start
Most websites are carrying more data than they need to, but it is not always obvious where that comes from. Images, third-party tools, and legacy content all play a role. Starting with a basic measurement gives you a clearer picture. Once you have that view, you can focus on the changes that will have the most impact. That might be reducing image sizes, removing unnecessary assets, or simplifying how pages are built.
From there, it becomes an ongoing process. Review, improve, and repeat. Over time, that leads to a website that is lighter, faster, and easier to manage. The good news is that images are typically fairly easy to take control of, meaning you can start seeing improvements as quickly as overnight. Those improvements aren’t just limited to CO2 reduction either, your site will load faster, and every single inbound marketing channel benefits from sitespeed. Search engines favour faster sites, your page quality score for paid campaigns improves, and your bounce rates reduce. It’s a no brainer!
Need help understanding where you currently stand? Get in touch to discuss a digital sustainability audit, and we’ll help you to start making the right changes today.
