Both tools mock HTTP APIs. They start from opposite ends of the workflow: Mockoon hands you a GUI to write fixtures by hand. Gostly records the traffic your service already sees and serves that back.
Mockoon is, by a comfortable margin, the best free desktop mocking GUI on the market. It is MIT-licensed, ships as a clean Electron app with a CLI for CI, and lets a single developer compose a working mock for a single API in minutes. Around 1.6M downloads and a strong community speak for themselves.
Gostly is a different shape of product. Instead of a desktop tool an individual developer drives, Gostly is a server-side proxy a team drops in front of an upstream API. It records every real request and response in LEARN mode, then replays them in MOCK mode. AI fills in unrecorded requests, but it is grounded by the recordings — not free-running on a text prompt.
The choice is rarely about features and almost always about workflow. If one developer is mocking one API and the JSON shape is small enough to type, Mockoon is the lighter, friendlier tool. If a team has multiple services whose responses keep drifting from whatever the mock said last sprint, Gostly is built around that pain.
| Feature | Mockoon | Gostly |
|---|---|---|
| Free, OSS desktop GUI | MIT | No |
| Free OSS proxy / server | No | FSL |
| Hand-authored fixtures (GUI builder) | Yes | No |
| Records mocks from real upstream traffic | No | Yes |
| AI-assisted endpoint generation | from text prompt | grounded by your traffic |
| CLI for CI | Yes | Yes |
| Team workspace + multi-seat sync | Cloud Team | Team plan |
| Latency / status-code injection | Yes | Yes |
| Stateful CRUD across requests | No | roadmap (Q4 2026) |
| Drift detection vs upstream | No | v1 today; canary-replay v2 Q4 2026 |
| Self-hostable | desktop only | single binary or K8s |
Roadmap items are explicitly labelled. We do not claim shipping features that are not shipping today.
Choose Mockoon when
Choose Gostly when
| Tier | Mockoon | Gostly |
|---|---|---|
| Free | Desktop app, MIT, unlimited | Unlimited services, OSS proxy (FSL) |
| Solo / Pro | $10 / mo (Mockoon Solo, 100–200 AI endpoints / mo cap) | $10 / mo single user (unlimited services, AI on miss) |
| Team | $100 / mo for 5 seats (Mockoon Team) | / seat / mo |
| Self-host / Enterprise | Mockoon Enterprise — custom | $499 / mo Self-host · $25K+ Enterprise |
At the Pro tier the prices are identical; the products are not. At the Team tier Gostly is $79/seat/mo versus Mockoon's $100 for five seats — so for very small teams Gostly tracks lower, and for larger teams Mockoon's flat block-of-five may be cheaper. The right comparison is workflow, not sticker price.
Drop in the proxy, record an hour of staging traffic, see whether replay-from-reality changes the calculus for your team.
Evaluating for a team of 3+? We’d love to talk before you commit.