Upcoming website migration ? How to do it sustainably - Dave the SEO

Missed Dave's Talk at the October 2025 Green SEO Event (Brighton SEO Fringe)? Well here is an extended version, more ideas to ensure your new site is built to be sustainable and you choose the best hosting options for performance and sustainability, saving energy, water, resources and cutting your carbon footprint along the way. Website Migrations are your one shot to make your website greener (and as a knock on faster and cheaper to run too).

Transcript

1. Upcoming website migration? Here’s how to do it sustainably. davetheseo.com linkedin.com/in/davecousin/ @davetheseo.bsky.social
2. If you’re not migrating, do what you can, But there’ll always be limitations Migrations are your one true shot to make your site sustainable NOW & for the FUTURE *(And in case your Stakeholders aren’t convinced you can save money and boost Sales too)
3. What this isn’t about Recycling your Old Site – Not fit for Purpose? Chuck it. & Let’s make that new site darn Sustainable
4. Introduction to Sustainable Web Design First a celebration: WSG is the framework we need: Though a bit late for this presentation https://www.w3.org/TR/web-sustainability-guidelines/
5. Intro to Sustainable Web Design The web & tools & sites that run on the web are getting more energy hungry But Sustainability is about more than just Carbon Footprint & Electricity usage Data Centres also consume: • Water, often in areas with water deprivation • Rare Earth Minerals & Resources used for making batteries & servers • With Environmental & Human Cost https://www.npr.org/2022/08/30/1119938708/data-centers-backbone-of-the-digital-economy-face-water-scarcity-and-climate-ris & https://www.latimes.com/world- nation/story/2019-07-28/china-rare-earth-tech-pollution-supply-chain-trade & https://www.kitco.com/opinion/2025-02-27/data-centers-growing-appetite-surging-demand-rare-earth-
6. Intro to Sustainable Web Design Many Platforms & CMS can be more sustainable or a disaster Depending on how they are set up & the site built Others are intrinsically Bad Some are particularly Good
7. Intro to Sustainable Web Design A well designed site on ‘bad’ hosting could be worse than a bad site on ‘eco-friendly’ hosting. DON’T assume that Big Hosting Company = BAD OR Small ‘Green’ Hosting Company = GOOD https://trellis.net/article/microsoft-mining-hard-drives-for-rare-earths/ & https://www.washingtonpost.com/climate- environment/2023/06/21/renewable-energy-credits-certificates-greenwashing/
8. Counting Calories What actually impacts use of energy for a website: Transmission Uses: • Electricity Data Storage Uses: • Electricity • Hardware Processing: Client Side & Server Side Uses: • Electricity • Hardware • Water
9. Counting Calories Transmission Energy Use Factors: • The More you send • The Further you send it • How you send it (e.g. Fibre vs 5G) • Number of Connections (+1kb per connection) • Caching Settings
10. Counting Calories Data Storage Resource Use Factors: • The more you store • Regardless of frequency used • The number of places it is stored • Efficiency of Edge caching (CDN)
11. Counting Calories Processing Resource Use Factors: • The amount of rendering, interactivity • Client-Side vs Server-Side • # of Database requests • Caching: Pages, snippets etc. Did you know? (Green) Server- side is generally more efficient & cuts transmission Reqs
12. Hosting Choices - CDNs Edge Caching is designed to be efficient • Only the files that get used locally on each server • Cache reflects demand • Transmission cost minimised • Way better than a server network (don’t do this) - Traffic +
13. Hosting Choices – Green Hosting Look Out! • Hosting providers using another service e.g. AWS? • Green Credentials don’t stack up? • Recycling Commitments? • Water Commitments? (Pollution, ground water use, water stress) • Data Centre Locations? (Brown or Green Field, Urban vs Rural, Climate) • Reusing waste heat?
14. Hosting Choices – Green Hosting Look Out! • Green Credentials don’t stack up? • Renewable vs RECs (Renewable Energy Certificates) or GOs? (Guarantees of Origin) • Create Additionality? • Look out for PPAs or similar (Power Purchase Agreements) • Or own Renewable Generation?
15. Hosting Choices – Green Hosting Availability of truly Green Hosting has been slow to become available for small companies. Own Renewables x2 Water Replenishment Managed Hosting Enterprise Co- Location Own Solar Generation Efficient data centre + CDN (e.g. Cloudfront) Enterprise Co- Location Hydro & Wind Projects inc. India & Europe Use of RECs, lack of Transparency S3 + Cloudfront
16. Easy to Fix Areas of Waste Opportunity: Browser Caching Tip: Check Cache Control How often must files be redownloaded? Check, images, fonts, CSS, etc. Tip: Don’t expire Images etc. Images never expire, instead update file names if a new image is needed.
17. Easy to Fix Areas of Waste Opportunity: Unused Code Tip: Legacy Code Unused code? e.g. styles? Features that were never used? Tip: Compiling How often is main JS and CSS recompiled? Does it remove unused code? Tip: Code for specific Pages Which code, e.g. styles, JS for interactivity, only used on a certain page(s)? e.g. Checkout? Move inline?
18. Easy to Fix Areas of Waste Opportunity: Page Design Tip: Image Sizes Resized for Viewport? Full Res for Thumbnails? Tip: Fonts Use standard/system fonts? Minimise # of Web Fonts (1-2)
19. Easy to Fix Areas of Waste Opportunity: Page Design Tip: Images vs Styles Check Dev Tools > Network for Design Element Images, e.g. gradient, buttons, corners Could these be rendered with CSS instead? Even animations can be achieved with CSS
20. Easy to Fix Areas of Waste Opportunity: Cut unnecessary Crawling Tip: Duplicate Content Handle Duplicate content with Canonicals Tip: Spider Traps Look out for things like indexable facets in search or products creating thousands of combinations. Block in robots or use ‘?’ parameters
21. Easy to Fix Areas of Waste Opportunity: HTTP/2 or HTTP/3 Protocol Tip: Avoid HTTP 1.1 HTTP/2 can handle multiple requests on 1 connection – c.+30% faster than 1.1 HTTP/3 establishes & maintains connections more efficiently c.+10-20% faster than HTTP/2 Check all resources, including third party.
22. Easy to Fix Areas of Waste Opportunity: Compression Tip: Use Modern img Formats WebP has compression built in -25-30% vs JPG Tip: Compress Text Based Files HTML, JSON, CSS, JS can be compressed by up to 70%
23. Easy to Fix Areas of Waste Opportunity: Third Party Scripts Tip: Review what you are using & Migrating Check legacy for unused scripts e.g. Heatmap, Social. What’s being used? What’s slow & bloated? Don’t migrate by default Tip: Use Google Tag manager (GTM) Use for: Easy management (on/off), Conditional firing, Don’t load before permission, Async Loading,
24. Performance Vs Energy Usage Choices Opportunity: Delayed Loading Tip: Use Lazy Loading Prioritise above first fold elements Other elements load only when scrolled within a %age of position Tip: Load on Click Setup YouTube, Maps etc. to show thumbnail and load applet only on click
25. Performance Vs Energy Usage Choices Opportunity: Consolidating Elements Tip: Consolidate Templates Ensure that your new site doesn’t create more templates than needed. 2-5 flexible templates may be sufficient. Tip: Reuse elements in multiple templates & pages Use the same design elements but also scripts. e.g. Use same audio player throughout the site.
26. Backend Opportunities Opportunity: Cut Database Requests Tip 1: Are all requests needed? Don’t make automatic DB requests unless they change the page Are hidden widgets, 3rd party tools etc. making requests?
27. Backend Opportunities Tip 2: Have cached pages & objects Have page version for cookieless users ready to serve. Serve the same version to search engine crawlers. Use Object Caching for query results that rarely change. Use tools such as Prerender that can work with most platforms to store and serve a cached page. c.60% of traffic is cookieless and can be served a cached page (40% Bots+ 20% uncookied humans) https://www.statista.com/chart/31516/how-respondents-handle-cookie-settings/ | https://prerender.io/blog/bot-vs-human-traffic/
28. Backend Opportunities Opportunity: Polling vs Pushing Tip: Use Push Notifications such as WebSockets Push notifications (from the server) to tell the front end to update are more efficient. Polling needs regular ‘check-ins’.
29. Backend Opportunities Opportunity: Server Side vs Client Side Rendering Tip: Is Server Side Rendering Possible? Transmit a rendered version of the page, less files means less transmission. Green, efficient data centres use less energy than users’ machines. Interactivity is still possible with some Client Side Rendering where needed.
30. Backend Opportunities Opportunity: Headless Tip: Use Headless + Static Site generator Uses API to pull content, e.g. JSON. Front & back end decoupled. Lightweight Static Site Generator creates cacheable HTML Avoid scripts, CSS etc. cut down what’s stored and transmitted.
31. Reducing Main Thread Work Opportunity: Review Scripts Tip: Break Up Long Scripts Stopping interaction may mean page keeps loading when user wants to click away / navigate Tip: Defer Non-Critical JS If a user is coming through a page just to navigate or to engage briefly, some JS may not need to run
32. Reducing Main Thread Work Tip: Avoid Unnecessary Loops Loops in scripts may keep main thread working for longer than needed without doing anything useful. Tip: Manage DOM Size, check node count and simplify Check node count. If high check for nodes & elements that don’t impact the site visually or for interactivity.
33. Measuring Energy Consumption Ensure Staging Hosting matches your planned live hosting for accurate results. Use traffic estimate to get Annual CO2 • Screaming Frog is easy to use with staging sites, uses co2.js, URL level ratings Quick / Free alternative https://www.websitecarbon.com/ • Enable JS Rendering • Set, under Spider > Advanced ‘Green Hosting Carbon Calculation’ if using Green Hosting • Complete Crawl • Go to Validation Tab • Check Carbon Rating & CO2 (mg) • Check Resources CO2 per Page & Size
34. Measuring Energy Consumption Don’t forget storage What is actually on your servers? Remember to delete/ archive all files for your legacy site Quick / Free alternative https://www.websitecarbon.com/
35. Recommended Add-Ons and Tools Akamai CDN / Edge Caching Img + Vid manager Lazy Loading Minify Remove Blank Spaces from JS, CSS Plugin for Wordpres s, Shopify & Others Lazy Load Can Code Manually Use Hosting Dashboar d Use Plugins WP Rocket Focused on Speed Caching Lazy Loading Removed unused CSS Image Formats More Dev Tools Lighthouse Coverage Network Performance Database Optimisers Add-Ons Exist for WP, Drupal, Joomla + More Save disk space and Requests Prerender Use for SSR Use to cut Database Requests with cached pages