Quick answer: Mockoon is a well-liked desktop tool for designing mock APIs, with strong templating, rule matching, and a CLI for CI. Powerduck is a local-first studio that generates the mock from your OpenAPI contract instead of asking you to hand-build routes. The difference is the source of truth and the drift that follows. Mockoon gives you precise manual control over a standalone mock; Powerduck guarantees the mock matches the contract, the tests, and the docs, and regenerates on save. Pick Mockoon when you want a dedicated, highly customizable mock designer; pick Powerduck when the mock should be derived from the spec and never quietly diverge.
This page compares the two honestly, including the CLI, cloud, and templating, and links to the focused guides. Start with the table, then read the sections that match how your mocks are maintained today.
The two at a glance
| Capability | Mockoon | Powerduck |
|---|---|---|
| Primary role | Desktop mock designer | OpenAPI studio with mock generation |
| How routes are created | Hand-built | Generated from the spec |
| Source of truth | The mock file | OpenAPI contract |
| Regenerates on contract change | Manual update | Yes, on save |
| Templating | Rich dynamic templating | OpenAPI examples and responses |
| CLI / CI | CLI, Docker, GitHub Action | OpenAPI CLI |
| Entry price | Free desktop; cloud paid | Desktop and Hub free |
| Best for | Fine manual control of a mock | Spec-synced mocks across the lifecycle |
Hand-built routes vs generated mocks
Mockoon is genuinely powerful for designing a mock: you decide every route, status, and response. The cost is that the mock is a separate artifact you maintain, and it drifts the moment the contract changes without anyone noticing. A generated mock starts from the spec, so the routes, parameters, and responses are correct by construction and update on save. The direct comparison is in Mockoon manual routes vs OpenAPI mocks, and the drift problem is in mock drift: Mockoon vs contract mocks.
Templating vs authored examples
Mockoon's templating is one of its strongest features, and it is the right tool when you need bespoke, dynamic responses that are not part of the contract. A spec-driven mock uses the examples and response schemas you already author, so the data the mock returns is the same data the docs show and the tests assert. The tradeoff is in templating: Mockoon vs OpenAPI examples.
CLI, cloud, and where the free tier runs
Both are usable in CI. Mockoon ships a CLI, Docker image, and GitHub Action, and a paid cloud for collaboration; Powerduck runs from the OpenAPI CLI and hosts mocks and docs together on the Hub within plan limits, so the hosted mock is never out of sync with the reference. The CLIs are compared in Mockoon CLI vs Powerduck CLI, and the hosting is in Mockoon cloud vs free Hub mocks.
Stateful scenarios and record-replay
Realistic workflows often need state — a create followed by a list, a token that expires. Mockoon supports scenarios and record-and-replay for exactly this. A spec-driven studio keeps the stateful behavior tied to the contract and the tests, so the same flow the agent exercises is the flow the spec describes. The scenarios are compared in stateful scenarios: Mockoon vs Powerduck, and the alternative to recording traffic is in record and replay vs spec mocks.
Where to go next
Powerduck is the local-first way to keep mocks synced to the contract; Mockoon is a strong dedicated mock designer. See it on the Powerduck homepage. For the wider picture, read the API mocking guide and the OpenAPI guide.
Frequently asked questions
Does Powerduck match Mockoon's templating?
Mockoon has richer bespoke templating for responses that are not part of the contract. Powerduck uses the examples and response schemas you already author, so the mock, docs, and tests share the same data instead of a separate template.
Can I run a generated mock in CI?
Yes. Run it from the OpenAPI CLI or as a container, just as you would with Mockoon's CLI. The difference is that the mock is derived from the spec rather than a separately maintained file.
Which is better when the API changes often?
A generated mock regenerates on save, so it cannot drift from a fast-changing contract. A hand-built mock gives more control but has to be updated by hand each time.
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