The guidance covers different aspects that can influence the sustainability of web content.

Explore the guidelines

Content purpose

Many of the most important sustainability impacts of a website are shaped by day-to-day content decisions made by content owners and editors. Every page view, image load, video play, or file download uses energy. Being purposeful about the content you put on the web can avoid unnecessary energy spent on loading digital assets that users do not need.  

This section provides recommendations on ensuring that your content achieves a clear purpose for users.  

Do 

  • Give each page one clear, primary purpose. This involves deciding what action, decision, or understanding users should take away. 
  • Use the title and opening paragraph to clearly explain what the page is for and what users can expect to find. 
  • Remove content that does not directly support the page’s purpose, including any that is outdated. Published information should be kept accurate and up to date. 
  • If content feels long or unfocused, first look for opportunities to simplify or remove what isn’t needed. Only consider splitting content into separate pages where this clearly improves user understanding. 
  • Share only the data users need. Check that published content follows data protection and privacy guidance.  

Don’t 

  • Create new pages without checking what already exists. 
  • Try to meet multiple unrelated needs on a single page. 
  • Include unnecessary background information or duplicate content already available elsewhere. 
  • Keep content simply because it exists. 
  • Use patterns, content, tools, or techniques that may artificially manipulate users into taking actions that are not in their best interest. 
  • Publish unnecessary personal or sensitive data. 

Responsible use of AI

AI tools can support content creation and editing, but they can also increase the volume of content and media produced. Some of these may be unnecessary or low-value content that increases page weight, storage and hosting requirements, user data transfer, and ongoing maintenance and auditing effort, thereby increasing overall environmental impact. In general, using generative AI to generate images and videos are more energy and carbon-intensive than generating text.  

Consider the environmental impact when using AI tools. Any AI-assisted content should continue to adhere to the basic content principles outlined in previous section above to allow users to achieve their purpose or reach their destination on the website as efficiently as possible, therefore improving sustainability. 

One example of positive AI use is in helping to summarise or simplifying content. Avoid using AI to make content longer without adding value, or to automatically expand content length without improving clarity or usefulness. 

Review and edit AI-generated content before publishing to ensure that any unnecessary or low-value content is removed, such as duplicate content or content that may not be useful to users. 

Lastly, avoid creating decorative AI-generated images or media by default. Use media that already exists as a preferred option. Consult the Asset Library in the first instance, or contact the Design team to discuss your needs.  

Content

Content that is unclear, outdated, duplicated, or unnecessarily complex can increase the time users spend on a site, trigger additional page loads, and lead to repeated visits or downloads. Over time, this results in avoidable environmental impact, and a poorer user experience. Hence, a sustainable web page should provide clear, inclusive content that meets the needs of the widest audience, and help users reach their destination as efficiently as possible. Some concrete ways to achieve this are to ensure language is easily understandable (‘readability’), as well as format and organise text in an optimal way for users to scan the page easily. 

Readability 

Do 

  • Keep in mind that there may be users who are non-native English speakers when you write content. 
  • Use short sentences and plain language as these are more understandable.  
  • Explain technical terms or acronyms on first use. 
  • Use consistent terminology throughout the page.
  • Provide sufficient context for users unfamiliar with Imperial systems or processes. 

Don’t 

  • Use jargon, unexplained acronyms, or technical language on pages targeting a general audience. 
  • Use idioms or culture-specific references. 
  • Assume prior knowledge or specialist understanding. 
  • Include background information that users do not need to understand the page’s key message

Further resources

The Flesch reading ease score may provide a useful guide on how readable your content is. There are tools such as the integrated readability functionality in Microsoft Word, Hemingway App, Grammarly or other similar tools available for you to check your writing for clarity and readability. If you choose to use these tools, especially those that use generative AI, please consider sustainability and data privacy implications before use. 

Formatting 

Organise and format content so it is easy to scan, read, and act on. 

Do 

  • Group related content clearly and make section titles descriptive. Use menus, headings, and links that clearly describe what users will find. 
  • Break long content into manageable sections. 
  • Use headings, lists, and spacing to help users scan.
  • Format content in a way that helps users understand easily and quickly what action they should take.
  • Help users explore efficiently. Highlight new content in a lightweight way, such as a “What’s New” section, so users can find updates without extra searching. 

Don’t 

  • Rely on visual styling alone (size, colour, bold) to structure content. 
  • Present long blocks of unbroken text. 
  • Repeat the same content structure or wording across pages without reason. 
  • Add content “just in case” if it’s unlikely to be useful. 

Other resources 

You can use data analytics tools, such as Google Analytics and the internal dashboards, to understand how users navigate your pages and whether they are achieving their intended purpose when they visit your page. You can also gather insights by testing content with smaller appropriate audience groups. Identifying areas where content may be unclear or difficult to find through these tools and methods can allow you to update your pages for a better user experience and improve sustainability. 

Links  

Links are meant to help users navigate between pages to find what they need. Broken or outdated links waste user time and system resources due to unnecessary page loads, thus increasing the environmental impact of web browsing.  

Some good practices include: 

  • Check links regularly and fix or remove broken ones. 
  • Use redirects only when content is moved or renamed to maintain user experience.  
  • Regularly review and remove redirects that are no longer needed to minimise unnecessary data transfer. Do not send users through unnecessary redirects or dead ends.

Media assets

Images 

Images play a crucial role on the web. They can: 

  • help users understand or contextualise the written content (e.g, photographs, illustrations) 
  • convey information (e.g. charts, infographics) 
  • act as visual cues (e.g. icons) 
  •  enhance visual appeal 

Images can be visually striking, but they also increase page size and energy use compared with plain text. Hence, use images effectively only where needed to achieve an intended outcome. 

If images are necessary, use JPEG (or WebP) as the preferred format. Do not use BMP, PNG, TIFF, SVG or other formats. If you have an image that requires a different format, please discuss your needs with the Digital Team.  

Crop or scale the image to the dimensions required for use in your chosen content type. You can use a free, open-source software like BeFunky to convert or scale your images.  

Audio, animation, and video 

Audio, animation and video can be effective ways to communicate information, but they are among the most resource-intensive content types on the web. They increase data transfer, processing load, and energy consumption, and may not be suitable for all users or devices. 

These types of media should only be used when it adds clear value and cannot be achieved more efficiently using text or static images. 

Do 

  • Use videos and animations only when they add clear value to the user experience, such as explaining a process or providing meaningful feedback.
  • Consider whether a static image, infographic, or simple CSS effect could achieve the same result. In terms of sustainability, static web elements typically fare better than audio, followed by optimised animations, then videos, in this order.
  • Keep videos and animations short, lightweight, and purposeful, if they are assessed to be necessary. They should be triggered only through a user action (e.g. click or tap), and users should have the autonomy to pause, stop, or disable them as they wish. Consider providing a description of what the video is about, as well as a transcript, to help users decide if they want to play the video. This also improves accessibility.  
  • Use CSS-based animations instead of video or JavaScript-heavy solutions where possible. 
  • Test animations across different devices to ensure they work without requiring high-end hardware. 
  • Review videos and animations regularly and remove those that no longer add value. 
  • Use lighter alternative formats of videos and animations.  
     

Don’t 

  • Use videos and animations that are purely decorative or distracting. 
  • Rely on videos or animations to convey essential information that could be provided in text. 
  • Include multiple videos and animations on a page if they compete for attention or performance.  
  • Auto-play videos or animations without user consent. Not all users want to or can view motion-based content. 
  • Use long-running or looping videos and animations that consume CPU and battery resources. 

Other file types 

Large files increase data transfer and energy use. Content editors should aim to keep files lightweight. Documents such as PDFs, Word files, spreadsheets, and other downloadable files can also significantly increase data transfer, storage, and energy use. Hence, if information can be presented as HTML, text, or a simple table, prefer that over a downloadable or embedded files. Avoid designing processes that require users to download or print documents unnecessarily. In case users print the webpage(s), support responsible printing with clean print layouts. 

If it is necessary to provide documents for users to download, these are the best practices to keep in mind: 

  • Explain clearly what the document contains before the user downloads it.  
  • Next to the download link, include the file type, size, and a short description of what the file is.  
  • You may also wish to include metadata that may be useful for the user to discern whether to download the file or not, such as last updated date and language. 
  • Use clear and meaningful file names so users can quickly identify the correct document. 
  • Use the lowest file size that still meets user needs, and never larger than 2MB.  
  • PDFs are preferred over large slide decks (.pptx) or other overly complex formats, as they are more lightweight. Avoid high-resolution files.  
  • Reduce file size before publishing by compressing images, documents, and media before uploading, removing unnecessary pages, and exporting optimised formats. 
  • Make documents viewable in the browser rather than forcing a download when the format allows it. Take care to avoid embedding files in ways that prevent browser caching or efficient reuse. 
  • Reuse a single version of a document instead of publishing multiple copies across the entire site. Avoid re-uploading the same large file multiple times or publish multiple versions of the same document(e.g. same document in PDF and .pptx). 

Content and data management

Storing content and data requires energy use and resources, which produce emissions and have an environmental impact. Hence, good data management helps content stay relevant, accurate, and ultimately sustainable over time.  

Use clear naming and version control for documents so that it is clear which version is the latest one, and which versions are outdated. Removing old or outdated versions helps to reduce the volume of data stored and thus reduces unnecessary energy use and resources.  

Having good data management practices ensures content is stored only when necessary and stored in an efficient and optimised way. Storing content in agreed shared locations rather than each person duplicating the content in their personal folders may utilise less resources.