Seven registries issue the credits that make up the voluntary carbon market, and buyers routinely talk about them as if they're interchangeable brands of the same product. They aren't. Here's what actually separates them, and what that difference means for a project you're evaluating.
- Registry size reflects market share and history, not credit quality. A small registry isn't automatically a weaker one.
- ART TREES stands apart structurally, crediting entire jurisdictions rather than individual project sites.
- Isometric is the newest major registry and the only one built specifically around durable removal methods rather than broad avoidance and reduction categories.
- The registry a project sits on matters less than the project itself. Use registry choice as context, not as the deciding factor.
The Seven Registries at a Glance
Every registry tracked in our carbon offset projects database falls into one of these seven. Project counts below reflect current tracked totals and will shift over time as new projects register.
| Registry | Projects tracked | Founded | Defining characteristic |
|---|---|---|---|
| Verra (VCS) | 4,983 | 2007 | Largest by project count, widest project-type range |
| Gold Standard | 4,105 | 2003 | Explicit weight on UN SDG co-benefits |
| Climate Action Reserve | 1,268 | 2001 | North American, strict protocol-specific methodology |
| American Carbon Registry | 979 | 1996 | Oldest registry, voluntary plus compliance-eligible |
| Cercarbono | 234 | 2016 | Colombia-based, Latin America focus, ICROA-backed |
| Isometric | 62 | 2022 | Durable removal only, newest major registry |
| ART TREES | 28 | 2018 | Jurisdictional scale, credits states and countries |
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Verra (VCS)
Verra administers the Verified Carbon Standard, the largest voluntary carbon registry by project count and the widest ranging by project type, spanning forestry, renewable energy, methane capture, agriculture, and more. Its scale is both its strength and the reason it draws the most scrutiny, a registry this large inevitably includes projects across the full range of quality, which is exactly why independent ratings matter more here than on smaller, more homogeneous registries.
Gold Standard
Gold Standard was established with backing from WWF and other environmental groups, and that origin shows in its methodology: alongside emissions reductions, it places explicit weight on UN Sustainable Development Goal co-benefits, things like local employment, water access, and biodiversity impact, as part of what a project has to demonstrate. Buyers specifically prioritizing co-benefit reporting, not just tonnes of CO2, tend to find more of what they're looking for here.
American Carbon Registry (ACR)
ACR was founded in 1996 as the first private voluntary greenhouse gas registry in the world, making it the oldest registry on this list. It works to create confidence in the environmental and scientific integrity of carbon offsets, and it covers both voluntary and compliance-eligible project types, meaning some ACR-registered projects can also generate credits usable in certain regulated compliance markets, not just the voluntary market.
Climate Action Reserve (CAR)
CAR traces back to 2001, originally established as the California Climate Action Registry before growing into a national and now broader North American registry. It's built around strict, science-based protocols and maintains a meaningful presence in both the US compliance and voluntary markets, with close ties to regulatory programs like California's and Washington's cap-and-trade systems.
ART TREES
ART TREES is structurally different from every other registry on this list. Instead of crediting individual project sites, the Architecture for REDD+ Transactions issues TREES credits at jurisdictional scale, crediting entire states or countries for forest protection and reforestation outcomes measured across their whole territory. That means an ART TREES credit represents a slice of a much larger, government-level forest protection program, not a single defined site the way a typical Verra REDD+ project does.
This jurisdictional structure is worth understanding before comparing ART TREES credits directly against project-level credits from other registries, they're answering a different question about scale and accountability.
Cercarbono
Cercarbono is based in Colombia and certifies climate, nature, and circular-economy projects, primarily across Latin America, with more than 190 projects currently in its certification cycle. It positions itself around a blockchain-enabled registry and streamlined certification timelines, and it's backed by ICROA, giving it recognized standing alongside the larger, longer-established registries despite its smaller current footprint.
Isometric
Isometric is the newest registry on this list, launched in 2022, and the only one built specifically around durable carbon removal rather than the broader mix of avoidance and reduction categories older registries cover. Its focus is technologies like biochar, direct air capture, and mineralization, with measurement standards built for that narrower, removal-specific category rather than adapted from a broader methodology base. It has also positioned itself as faster to work with than older registries, with new protocols developed in weeks rather than months in some cases.
Does the Registry Actually Matter?
Less than buyers often assume, and more than "just pick the biggest one" would suggest. Registry choice determines the methodology framework a project was built under and the geographic and category focus you'll find there. It does not function as a quality score. A rigorously-run project on a smaller registry like Isometric or Cercarbono can be a stronger buy than a poorly-executed project sitting on Verra simply because Verra has more total volume.
The practical approach: use the registry to understand what kind of project you're looking at and what methodology framework applies, then evaluate the individual project on its own merits, ideally cross-referenced against an independent rating from an agency like BeZero Carbon, Sylvera, or Calyx Global, and checked against ICVCM's CCP-Approved status where available. Registry first, then project, then rating, in that order, but never registry alone.
For the step-by-step version of that project-level check, see our carbon offset due diligence checklist.
Comparing projects across registries?
The CRBN.CREDIT projects database tracks 11,659 projects across all seven registries, with registry-reported issuance and retirement figures on every one.
Frequently Asked Questions
What's the difference between Verra and Gold Standard?
Verra's Verified Carbon Standard is the largest voluntary registry by project count and covers the widest range of project types. Gold Standard, originally backed by WWF and other environmental groups, places additional weight on UN Sustainable Development Goal co-benefits alongside emissions reductions.
Is a bigger registry automatically a better one?
No. Project count reflects market share and history, not credit quality. A registry's size affects how many project types and geographies you'll find there, not whether any individual project on it is well-run.
What makes ART TREES different from the other registries?
ART TREES operates at jurisdictional scale, crediting entire states or countries for forest protection, rather than individual project sites. That's a structurally different model from registries like Verra or Gold Standard, which credit specific, individually defined projects.
Which registry should I buy credits from?
The registry matters less than the individual project and its independent rating. A well-run project on a smaller registry can outperform a poorly-run project on a large one. Registry choice should follow project quality, not the other way around.
What is Isometric and why is it newer than the others?
Isometric is a registry focused specifically on durable carbon removal methods like biochar and mineralization, applying measurement standards built for that narrower category rather than the broad range of avoidance and reduction project types older registries cover.
A note on this article. Project counts reflect the CRBN.credit database as of September 2026 and will change as registries add and update projects. This comparison describes registry structure and focus, not a ranking or quality assessment of any individual registry or project, and is for informational purposes rather than investment advice.