Comparison
Carbon vs Prism
Prism turns an OpenAPI spec into a mock server in one command. It is the fastest way to get a spec-driven mock on a port. But Prism is deliberately stateless — POST /pets returns an example, and GET /pets afterwards does not include the pet you just created. Carbon starts from the same spec and models the state so those two calls agree.
Capability by capability
Rows below are checked against Prism's public docs. Where support is "partial" we say what's actually there.
| Capability | Carbon | Prism | Notes |
|---|---|---|---|
| State persistence across requests | Prism responds from spec examples; it does not track created resources. | ||
| Snapshots / rewind (state journal) | |||
| Chaos / failure injection | Can return any spec-documented status via the "Prefer" header; not a chaos preset system. | ||
| Multi-format ingest (OpenAPI, GraphQL, HAR, Postman, gRPC) | OpenAPI 2/3 only. | ||
| Local-first (runs on your laptop) | |||
| No hosted-service dependency | |||
| Framework glue (vitest, jest, playwright) | CLI is easy to boot from a test, but no first-party JS test bindings. | ||
| Drift detection vs real API | Prism has spec validation of live traffic; not the same as diffing shapes across runs. |
When to pick Prism
- You just want to eyeball your OpenAPI spec by hitting it with curl.
- Your consumers only need one canned example per endpoint.
- You want spec-conformance validation in front of a real backend.
When to pick Carbon
- A POST followed by a GET must return what you just created.
- You want to test error paths, latency, and outages without editing the spec.
- Your spec is not OpenAPI (GraphQL, HAR, Postman, gRPC).
Try Carbon against your own spec.
One command turns any OpenAPI, GraphQL, HAR, Postman, or gRPC spec into a stateful local server. See how it compares to Prism on the endpoints you actually ship.