How to reduce your website's carbon footprint
Most heavy websites are heavy for the same few reasons. Most of the fixes change nothing a visitor can see. The rest are choices, and they are usually the biggest savings of all.
9Fixes: nobody will notice.
Oversized images.
Many websites send phones the same huge photo they send big screens: a picture shown 400 pixels wide that is really 4,000. Make a copy at the size each screen shows it, and phones download a fraction of the data.
Old image formats.
Most photos are still sent as JPEG or PNG. Newer formats such as WebP and AVIF look the same and are often a third to a half smaller. Every modern browser supports them.
Images loaded too early.
Pictures far down a page are often downloaded the moment it opens, even if no one scrolls that far. Let them load only when a visitor is about to see them.
Too many web fonts.
Many websites download every version of their font, though the page uses two or three. Each one is a separate download. Keep the ones you use, or use the fonts already on every device.
Uncompressed files.
Code and text can be squeezed for the journey and unpacked by the browser, often to a quarter of their size or less. It is usually one setting on the server, and many websites have it switched off.
Files downloaded again.
When a visitor moves to a second page, their browser should reuse what it already has. Many websites tell browsers not to, so the same files download again on every page.
Page builder overhead.
Website builders and themes often load code for every feature they offer, used or not. Switch off what you don’t use, or choose a lighter theme.
Code that never runs.
Many pages download code for features they don’t have, because one big bundle goes to every page. Send each page only what it needs.
Shared compression dictionaries.
A newer technique: later pages download only what is different from the page before. Chrome and Edge support it today; other browsers simply get the normal page.
4Choices: you decide.
Autoplaying video.
A video that plays by itself is often the heaviest thing on a page, many times more than everything else. Show a still picture, and play the video when someone taps it. Visitors who want it lose nothing.
Chat windows.
Chat and help bots often download hundreds of kilobytes, sometimes megabytes, on every page before anyone asks for help. Show a small chat button and load the chat when someone taps it.
Social add-ons.
Embedded Facebook, Instagram or YouTube boxes load another company’s code on every visit. A plain link takes visitors to the same place and downloads almost nothing.
Marketing tags.
Of the 34 websites we scored, 34 load Google Tag Manager (typically 0.55 MB), 32 load Facebook’s code (0.22 MB) and 8 load TikTok’s (0.16 MB). Google Tag Manager alone weighs about 68 times this whole page.
If you no longer market through a channel, remove its tag. Check what each remaining tag loads: many keep loading old campaigns no one looks at.
Some websites go further: one small tag sends visitor activity to their own server, which passes it on to Facebook, Google and the rest (server-side tagging). Visitors download one tag instead of many.
Your profile lists your five biggest savings, largest first. Make the changes, and next month’s measurement shows the difference.