Why this glossary matters for SEO teams

Search teams make ranking decisions based on discoverability and user experience. Those same technical signals determine server load and device work which in turn drive energy use and carbon emissions. Understanding precise definitions and metrics helps teams measure impact, prioritise fixes that improve both search and sustainability, and report results in a verifiable way.

How to use this glossary

Use the terms below when you write audits, define targets, or compare tools. For each metric the entry explains what is measured, the typical unit, how to collect it, and how SEO teams should interpret it. When you see a formula it is presented in general form so you can adapt it to your telemetry and regional grid data.

Core metrics and terms

• Website carbon footprint

  The total greenhouse gas emissions attributable to a website for a given boundary and period. Emissions can be reported as absolute totals for an organisation, as emissions from an application or service, or as emissions per visit. Reporting requires a defined scope, a measurement method, and clear time boundaries.

• Per visit emissions

  Emissions divided by the number of visits during the same period. Unit is grams of CO2 equivalent per visit or gCO2e per visit. This metric normalises traffic so teams can compare pages, templates, and campaigns regardless of volume. Calculate it by dividing total operational emissions attributable to web traffic by visit count for the chosen period.

• Per page view emissions

  Similar to per visit emissions but divided by page views rather than visits. Use this when comparing template variants or content types that drive different numbers of page views per session.

• Operational emissions

  Emissions from the electricity used by servers, network equipment, caches, and end user devices while serving and consuming the website. Most website calculators focus on operational emissions and exclude embodied emissions unless explicitly stated.

• Embodied emissions

  Emissions associated with manufacturing, shipping, and disposing of hardware such as servers and end user devices. These are often part of broader organisational reporting but are typically omitted in per visit web calculations unless you adopt a full lifecycle boundary.

• Grid carbon intensity

  The mass of CO2 equivalent emitted per unit of electricity generated in a given electricity grid, typically expressed as grams of CO2 equivalent per kilowatt hour or gCO2e per kWh. Grid intensity varies by country and by time of day when the grid has higher or lower renewable contribution. Use reliable regional or temporal datasets when converting energy to CO2.

• Energy per visit

  Electrical energy consumed per visit measured in kilowatt hours per visit or kWh per visit. Multiply this by grid carbon intensity to convert to grams of CO2 equivalent per visit. Energy per visit can be estimated from server energy profiles plus an estimate of network and device energy.

• Data transfer per visit

  Total bytes transferred from origin and CDNs to the client during a visit. Measured in bytes or megabytes per visit. This metric correlates with network energy and influences page speed metrics that matter for SEO.

• Client device energy

  The electrical energy consumed by a visitor device to parse, render, and execute page code. Device energy depends on device type, CPU work, rendering complexity, and screen technology. Estimating device energy requires device class assumptions or measured samples.

• Server energy

  Electrical energy consumed by origin and backend systems to serve requests. This includes web servers, application servers, databases, and any background compute invoked during a visit. Measure server energy via provider reports, direct metering, or modelled estimates based on CPU utilisation and instance types.

• Network energy

  Energy used by the network infrastructure to carry data between servers and clients, including ISPs and backbone providers. Network energy is often modelled from data transfer volumes and published energy per byte factors for different network segments.

• CO2 conversion formula

  A simple conversion from energy to carbon is grams CO2e equals kWh multiplied by grid intensity in gCO2e per kWh. Use consistent units and a documented source for grid intensity. Example form: gCO2e = kWh * gCO2e per kWh.

• Scope 1, Scope 2 and Scope 3

  Framework categories from common greenhouse gas protocols. Scope 1 covers direct emissions under organisational control. Scope 2 covers purchased electricity consumed by the organisation. Scope 3 covers indirect emissions in the value chain such as cloud provider electricity or the energy used by customers to browse a website. When attributing website emissions, server energy often sits in Scope 3 if using cloud hosting.

• Carbon intensity of hosting

  A combined metric describing how much CO2e is emitted per kWh used by hosting infrastructure after accounting for the provider mix of generation and any contractual renewable electricity. Providers may report residual mix or claim matching using certificates. Verify provider statements when using them in calculations.

• Renewable energy certificate

  Market instruments like certificates that represent the generation of renewable electricity. Certificates change accounting for the buyer and issuer. Distinguish between physical real time matching and certificate based matching when treating a host as low carbon.

• Time of use emissions

  Emissions calculated on an hourly or sub hourly basis using the grid intensity at the time each request was served. Time aware calculations can show lower emissions when traffic shifts to periods with more low carbon generation.

• Page weight

  Total bytes of all resources required to render a page including HTML CSS JavaScript images fonts and other assets. Page weight strongly influences data transfer per visit and often server and network energy. Reducing page weight is an action that benefits both speed and carbon.

• Core Web Vitals

  Performance metrics that measure user perceived loading and stability. Core Web Vitals include metrics such as Largest Contentful Paint and Cumulative Layout Shift. Faster Core Web Vitals generally indicate less device work and often lower per visit energy, making them relevant to both SEO and sustainability goals.

• Crawl emissions

  Emissions attributed to search engine crawling activity. Crawl emissions depend on crawl frequency size of content and the efficiency of server response. Reducing unnecessary crawling with proper sitemaps robots rules and cache headers reduces server load and associated emissions while preserving discoverability if done carefully.

• Carbon per conversion or carbon per revenue

  Business level metrics that divide emissions by conversions or revenue attributed to the website. These metrics help prioritise optimisation where environmental and business outcomes align. Choose the attribution method consistently and document assumptions.

How to measure responsibly

Measurement requires clear boundaries and documented methods. Decide whether to include only operational emissions or to add embodied emissions. Choose a time window and the traffic segmentation you will report on. Use verifiable data sources for energy consumption and grid intensity. When modelling server or network energy, prefer provider reports or measured telemetry over generic factors when possible.

Practical measurement steps

1. Define scope and boundary for the site or property you measure.

2. Collect traffic counts for the measurement period including visits and page views.

3. Measure or estimate data transfer per visit using logs synthetic testing or analytics that include resource sizes.

4. Estimate energy per visit by combining server energy estimates network energy per byte and device energy where relevant.

5. Apply a credible grid carbon intensity value for the region and period you are reporting.

6. Divide total emissions by visits or page views to calculate per visit or per page view emissions.

Decision criteria for SEO teams

Pick metrics that align with stakeholder needs and are actionable. Per visit emissions are useful for teams comparing pages and templates. Carbon per conversion helps product and marketing teams prioritise ROI aligned changes. Track page weight and Core Web Vitals because they are both actionable and correlated with lower energy use and better search outcomes. When suppliers claim low carbon hosting verify the claim with a combination of published residual mix data and independent evidence.

Common pitfalls to avoid

Do not compare per visit numbers without ensuring the same boundary and grid intensity. Avoid using certificate based claims as a direct substitute for actual time of use matching unless you state that accounting choice clearly. Be cautious about precise device energy claims unless you have measured representative device populations because device energy varies widely by model and user behaviour.

Example reporting dashboard components

A practical dashboard for SEO and sustainability should show per visit emissions with confidence bounds, page weight median and distribution, Core Web Vitals for prioritized templates, data transfer per visit for key page types, and carbon per conversion for business prioritisation. Include the assumptions used to convert energy to carbon and a link to the data sources or queries used.

Where to learn more

Look for organisations that publish methods and open data for grid intensity and for web specific calculators that document assumptions. When evaluating external tools check that they let you change grid intensity time of use and the hosting emission factors so you can reproduce the numbers with your own telemetry.