CometWeb Insight
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Audit your site in InsightCometWeb Labs / Carbon Badge
Small component.
Your footprint, visible.
Show visitors your page’s estimated CO₂e in a lightweight component that fits your website.
Free, with no account or API key. The badge calculates in the visitor’s browser. It sends no page URL or measurement data to Insight. MIT-licensed source.
cometweb.ioComponent preview
Calculated locally for this page. N/D means incomplete data — not zero emissions.
MIT · Web Component
Source and documentation on GitHubINSTALLATION
Choose a look. Paste the code.
Choose the theme and size in the preview above. No account or server setup needed.
1. Choose where to host the file
The browser downloads a pinned static file from cometweb.io. It calculates on-device, without requesting Insight scans.
Download ESM file v2.0.1 · SRI integrity check includedThe badge writes no cookies or localStorage. File downloads are subject to ordinary hosting logs. Cross-origin resources may hide their size — in that case the badge shows N/D.
2. Paste before the closing body tag
<script type="module" src="https://cometweb.io/scripts/carbon-badge/2.0.1/cometweb-carbon-badge.esm.js"
integrity="sha384-fjg7RaM8cI8U2Bpq+dPBzwKPLEuDTmjHbezvNYhYydb5ug2Wm3IIZo5ZGYWDEw0a" crossorigin="anonymous"></script>
<cometweb-carbon-badge mode="estimate"
theme="dark" variant="default"></cometweb-carbon-badge>If your site uses CSP, allow the chosen script origin in script-src. The estimate describes the current page load and can vary between devices.
DATA SOURCE
Where does the result come from?
The badge estimates one page load. Insight helps you find and prioritise improvements.
mode="estimate"An estimate in the browser
The component uses the local Performance API. It makes no result request and does not use the URL attribute to determine page weight.
Default · no server scans · incomplete data = N/DSWDM v4CO₂e estimation model
No APIlocal calculation, no runtime dependencies
dark / lighttwo component themes
MITmodify and self-host the source
DETAILS
Settings and score bands.
Attributes
modeestimate — default local modethemedark | lightvariantdefault | compact | minimalurlNot needed. The local badge uses the current page, excluding query parameters and fragments.Score thresholds (g CO₂e / page load)
A+< 0.10g
A< 0.20g
B< 0.40g
C< 0.70g
D< 1.00g
F≥ 1.00g
The grams of CO₂e come from the SWDM v4 model; the A+–F letter bands are our own presentation scale, not thresholds published by Sustainable Web Design. This estimates page transfer emissions — not an org-wide footprint or ESG certificate.
No. It displays a CO₂e estimate based on a model and available data. It is not an energy measurement, certification or ESG report.
Browsers do not always expose every resource size, especially for other domains. Check Timing-Allow-Origin headers with your resource providers. If data is still missing, the badge stays ungraded instead of guessing.
Neither. It downloads the component file and calculates locally. You can also host the file on your own site. It writes no cookies or localStorage.
Yes. The source is MIT-licensed. You can modify it and host it yourself while retaining the license notice.
Pairs with