Spec Versions
Which UCP spec versions are stores running? Track version adoption and drift across the ecosystem.
The Universal Commerce Protocol uses date-based versioning (YYYY-MM-DD). The protocol, capabilities, and extensions version independently — so a store can run the latest checkout capability while staying on an older protocol version. Stores can also declare supported_versions for backwards compatibility. Validate your manifest against any version with the UCP Validator.
2026-08-25
Also supports: 2026-01-23, 2026-04-08, 2026-08-25
2026-04-08
Also supports: 2026-04-08, 2026-01-23
2026-01-23
Also supports: 2026-01-23, 2026-01-11, 2026-04-08
2026-01-11
UCP spec versioning
How does UCP versioning work?
YYYY-MM-DD format. The protocol itself, individual capabilities, and extensions can all version independently. Adding optional fields or new endpoints is backwards-compatible; removing fields or changing types is a breaking change.Can a store support multiple spec versions?
supported_versions for backwards compatibility. Each supported version has its own profile URL, allowing agents to negotiate which version to use.What happens when the spec version changes?
dev.ucp.* capabilities version with the protocol by default, while vendor capabilities (com.{vendor}.*) version independently. Stores should update their manifest version when they adopt a new protocol release.Explore Protocol Data
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