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Carbon Emissions of the Web’s Most Popular Sites

Discover which websites are the ‘dirtiest’ when it comes to carbon emissions per visit as well as the most eco-friendly options on the web.
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Keyboard with 'zero emissions' written on enter key

Even the most environmentally conscious people might not be aware that a person’s carbon footprint, the amount of carbon released into the atmosphere as a result of your day-to-day life, is also impacted by their virtual life too. 

Everything, from internet shopping to sending emails to streaming content produces carbon emissions which negatively affect the environment and can lead to climate change.  

But not all online carbon footprints are equal – in fact there’s a stark difference in emissions between some of the world’s most popular websites. To learn more, we used the Website Carbon Calculator to discover which site’s homepage uses the most energy to load, not forgetting to bear in mind factors such as whether the data centre is using green energy. 

So, which websites are the ‘dirtiest’ when it comes to carbon impact, and which are the most eco-friendly? Read on to find out more...

Sites with the Highest Carbon Footprint

Looking at the 200 most popular websites in the UK, the environmentally dirtiest is the self-titled ‘front page of the internet’, Reddit. The website is used by millions of people around the world as a place to share news, content and discussions. According to the data, a single visit to the website leads to 13.05g of CO2 emissions. There are estimated to be around 430 million monthly active Reddit users worldwide, so just one homepage visit for all of those people would equate to over 5,611.5 tonnes of carbon emitted every month. That’s the same amount of energy it takes to power around 2,374 homes for a whole year. 

The second dirtiest website in the UK is the ideas and inspiration platform, Pinterest, which emits an estimated 12.43g of carbon with every homepage visit. With around 415 million active monthly users, a single homepage visit from each of these would equate to around 5,157.5 tonnes of monthly carbon emissions. 

The Cleanest Websites In The UK

Taking the top spot as the cleanest website is one of the most visited online resources in the world, Wikipedia. The website produces an estimated 0.04g of carbon per visitor. It seems the simplistic design of the site has a positive impact on its environmental footprint, which is hugely beneficial, considering the site receives an estimated 5.83 billion visits a year. 

LinkedIn, the professional social network, comes in at second place – emitting 0.23g of CO2 for every visit, and international fashion brand H&M follows closely behind, with 0.29g of carbon being emitted with each visit to their site. 

Sites with the Highest Carbon Emissions

Popular sites in the US see a very similar picture to the UK, with Reddit, Pinterest and Nintendo topping the list for the worst carbon output per homepage click. The US list does, however, include some America-specific brands, including electronics store Banggood and homewares providers such as Kohls and Home Depot. 

The Cleanest Websites In The US

When it comes to the cleanest sites, it’s also a very similar view to the UK’s list, although the US is, understandably, missing some home-grown British brands like Marks and Spencer. Instead, some of the lowest emission sites in the US include Dominos, FlipKart and the Japanese website platform Fc2. 

Carbon Emissions of Websites By Industry

You may find that you commonly visit certain types of sites more than others – perhaps you’re a social media lover, or are regularly eyeing up clothing sites to keep your eye on the latest trends. A lot of us have also been spending a lot more time on certain sites to help facilitate working from home. To dig a bit deeper into the carbon emissions of different websites, we broke the data down by industry. Read on to find out the best and worst offenders…

Social Media

Many of us sign into our social media profiles every day, and there’s been much discussion around the effects these platforms can have on our mental wellbeing. However, it may be that you haven’t considered the environmental impact that just logging on to your favourite network might have. 

One of the world’s most popular instant messaging apps, Viber, has well over a billion members with over 260 million of those being monthly active users. However, it tops our list of social media sites with the highest carbon output, producing over 13g of carbon per view. 

On the other end of the scale, video making and social networking service, Triller, has an impressively low carbon emission level of just 0.02g per view (the lowest of any website featured in our research). While it may be beaten in popularity by its similar rival TikTok, it proves to be a far more environmentally friendly option. 

Home Working

An abundance of previously unknown or underused sites have sprung into popularity over the last year, seeing a surge in use thanks to a dramatic increase in remote working. As a whole, home working websites fared pretty well compared to other industries, with even the higher emitting sites still boasting only moderate figures. 

While we weren’t able to track the figures for every home working site, from those in our list, it was clear that file sharing platform DropBox produces the most amount of carbon, with 7.35g emitted per visit. 

Meanwhile, project management and internal communication tool Basecamp boasted the lowest emissions with 0.23g of carbon released per visit. 


Although always popular, entertainment and streaming sites, regularly used for watching TV, lounging with a movie, reading reviews or gaming, have also seen an increase in use over the last year, as we’ve all spent more time seeking recreational fun in our homes. 

Japanese gaming company Nintendo releases the highest amount of carbon in this category, with a carbon emission of 11.43g per visit to their website, much higher than the rest on the list. Amazon’s movie and series-streaming service Prime Video can proudly hold the title of lowest carbon emissions per visit within the entertainment industry, producing just 0.38g for each click. 


Whether it’s groceries or takeaways, having food delivered to our homes has been a lifeline to help many people enjoy their favourite dishes over the last year. But what cost could these sites be having from a carbon perspective?

Diet company Slimming World, whose site contains recipes and tips, produces the most amount of carbon in our food industry list, emitting 3.26g per homepage visit. At the other end of the scale, multi-restaurant delivery service Deliveroo can claim to be the most environmentally-friendly website from our list, producing a minimal 0.45g per click.


Renowned for its beautiful underwear and impressive live fashion shows, Victoria’s Secret is one of the world’s most iconic lingerie brands. It’s also one of the highest carbon emission sites in the fashion category, producing 6.64g of carbon per homepage click. 

At the other end of the scale, budget-friendly clothing retailer H&M may be known as a fast-fashion outlet, but its website is the lowest in the industry for carbon emissions, with only 0.29g per visit. 


Travel is rarely an industry applauded for being carbon-friendly, with long haul flights generating more carbon emissions than the average person produces in a year. However, when it comes to their websites, they’re comparatively low on the emissions scale when likened to other industries. 

The highest carbon producer is Qatar Airways, but with their 3.16g per homepage click figure being the highest number on the list, that’s still fairly impressive considering many other sites clock in well over four times that amount.  

Meanwhile, travel and holiday aggregator Rome2Rio is the cleanest site in the travel category, with 0.32g of carbon emitted per homepage visit.


Another industry that has historically been associated with high emissions (although modern technologies are definitely showing huge environmental improvements), our automotive category produced some interesting results. We’d expected to see electric vehicle and clean energy company Tesla topping the bill of cleanest sites, but it actually featured as the 7th worst in the industry, with 2.79g of carbon produced per homepage click. This was, however, markedly lower than Mazda, which was by far the highest carbon emitter with 16.19g per visit. 

At the other end of the scale, Japanese car manufacturer Honda was able to take top spot for cleanest website in its category, with 0.71g of carbon produced per homepage visit. 


And finally, another business type which has been historically notorious for a questionable environmental impact is the cosmetics industry, although many brands have tried to make moves towards more ‘green’ ingredients and production methods in recent years.

American make-up and skincare brand Clinique's website produces 9.63g of carbon per homepage visit, making it the highest emitter in the category. Meanwhile, affordable skincare brand The Ordinary is the cleanest in the industry, producing 0.67g per click.

Armed with this new knowledge about the dirtiest and cleanest sites on the web, do you think you’ll change your online behaviour? One step could be finding a broadband or energy supplier that has eco interests at heart. Compare green energy deals to find out more.

Want to understand the impact of your own carbon footprint? Head to our carbon footprint calculator.


All carbon estimations are based on data from Website Carbon and are correct as of February 2021. Carbon emissions of sites may change due to changes to the website. 

The top websites in the UK and US were based on SimilarWeb’s top 200 websites. Pornography sites were removed.  Industry specific lists were also compiled using a seed list of most visited sites by sector in the UK from SimilarWeb. 

Not all sites could be scanned using the Website Carbon calculator.