Comparison
CO2.js vs Kepler
CO2.js vs Kepler: JavaScript library for estimating the carbon emissions of digital services and website visits. Prometheus exporter that measures…
Carbon-Aware Computing · both listings verified
| Field | CO2.js JavaScript library for estimating the carbon emissions of digital services and website visits. | Kepler Prometheus exporter that measures Kubernetes pod and node energy consumption. |
|---|---|---|
| Pricing model | Free | Free |
| Pricing published | Public pricing | Public pricing |
| Starting price | Free | Free |
| Licensing | Open source | Open source |
| Pricing details | Apache License 2.0; published as an npm module by The Green Web Foundation, with bundled carbon intensity data under CC-BY-SA and ODbL terms. | Apache License 2.0; distributed as an open-source project in the sustainable-computing-io organisation on GitHub. |
| Free tier | Yes | Yes |
| Assets covered | ||
| Platforms | Web | Cloud, On-premise |
| Region support | Global | Global |
| Compliance | Not stated | Not stated |
| API available | Yes | Yes |
| Last verified | 2026-10-22 | 2026-10-22 |
Editor's take on CO2.js
Fits web and product developers who want byte-level carbon estimates and green-hosting checks inside JavaScript applications, once a page or request has been measured. The trade-off is the model: emissions are estimated from data transferred combined with a grid-intensity model or hosting lookup, not from server-side measurement, so savings attributed to code changes depend on traffic assumptions matching real usage. It is a library, so dependency updates and reporting logic stay with the integrating team. Teams needing audited, organisation-wide accounting should feed its figures into a reporting platform.
Read the CO2.js listingEditor's take on Kepler
Fits platform teams running Kubernetes that want pod- and node-level energy metrics alongside existing Prometheus telemetry. The trade-off is attribution: it reads hardware power sensors and distributes that power across containers, so figures are estimates derived from sensor readings rather than per-container measurement, and accuracy tracks its attribution model. It exports metrics only, so carbon conversion, dashboards and reporting live in whatever stack consumes Prometheus. Clusters with virtualised or shared GPUs, or teams wanting a managed service, should verify support before relying on it.
Read the Kepler listingJudgement is written by the editor. Paid placements never change the ranking or the recorded field values.
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