Carbon offset at checkout — CarbonClick vs EcoCart vs Cloverly?

Three good options, each best for a different shape of brand:

• EcoCart — US-strong, best default-on UX. Cart-weight + shipping-zone math runs automatically. Default-on attach rate 30–55% vs <5% opt-in. Pricing: free for the brand (offset cost passed to customer at ~$0.40–$2/order) or absorbed by the brand. Magento integration via official extension or REST API. Best for $1M–$50M GMV DTC.
• CarbonClick — NZ-founded, AU/NZ/EU strong. Cleaner project transparency (customer sees which reforestation/cookstove project funded their offset, with certificate ID). Pricing similar. Magento integration via custom REST. Best for brands with European customer base sensitive to project provenance.
• Cloverly — API-first, dev-friendly. Best for brands who want to ship offsetting as a deeper UX (e.g. offset previewed at PDP, not just checkout). Pricing: per-API-call + offset cost. Magento integration via custom module. Best for technically mature teams who want differentiated UX.

Math matters: at $2/avg-order with 40% attach, a 50k-order/yr brand offsets ~10,000 orders ($20k/yr in offsets purchased) — customers fund it, brand gets the certification halo + the public-disclosure marketing.

The trap: default-on without disclosure is illegal under EU Green Claims Directive (must show cost + project + opt-out). Default-on with disclosure is fine and is the math-winning pattern.