Echo
We build APIs every day, so we wanted more than a place to send requests. Echo makes every response clear, lets your team publish a mock URL while the real service catches up, and shows when a contract change could break an integration.
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Google PlayBuilt for the work, not for the demo
Echo is a desktop client for testing HTTP and gRPC APIs. It opens fast, it stays out of your way, and every request you send comes back readable, with the status, the timing, and the body laid out so you understand it at a glance. Organize your requests into collections, keep your environments tidy, and stop hunting for the call you made last week.
- Test HTTP and gRPC APIs from a fast, native desktop client.
- Read every response at a glance: status, timing and body, laid out clearly.
- Organise requests into collections and keep environments tidy.
- Find the call you made last week without hunting through tabs.
See the difference, side by side
The feature we are proudest of is the one we needed the most. Point a single request at two environments, your staging and your production for example, run them together, and Echo shows you both answers next to each other with every difference highlighted. The moment something behaves differently between environments, you see it plainly, instead of guessing.
- Point one request at two environments and run them together.
- See both responses side by side with every difference highlighted.
- Catch a config drift between staging and production the moment it happens.
Serious where it matters
Echo carries the things teams genuinely need and usually have to pay dearly for: shared workspaces, real access control, single sign on, and an audit trail you can stand behind. It signs in with your Gapfy account and sits comfortably beside the rest of the family. Enterprise care, without the enterprise theatre, because solid tools should never be a luxury.
- Shared workspaces and real access control for your team.
- Single sign-on and an audit trail you can stand behind.
- Signs in with your Gapfy account, beside the rest of the family.
From first request to working integration
Call the real API, build against a mock while it takes shape, and see what a contract change could break. Echo keeps that work in one place.
Five protocols, one editor
HTTP, gRPC with real reflection-based transport, GraphQL with introspection and subscriptions, WebSocket with a binary hex view, and SSE with auto-reconnect. No plugins, no context switching.
Compare across environments
Fire the same request against up to 4 environments in parallel. Side-by-side responses with a structural JSON diff and synced scrolling show exactly what changed.
Collections built for teams
Spaces, infinitely nested folders, drag and drop, bulk operations. Share with your team at Read, Contribute or Full Access, with in-app people search.
Environments and variables
Space-scoped environments with secret variables and a global active-environment picker. Live {{variable}} highlighting and autocomplete keep every request readable.
Automation without ceremony
Run collections and chain requests with JSONPath. Mock calls inside Echo, or publish a public mock URL that answers after the desktop closes. Schedule checks and script with pm.* when you want code.
Private by design
Guest mode works offline with no account and no limits on the local loop. The entire local database is encrypted at rest.
Sync that follows you
Collections, environments, schedules, mock servers and even deletions sync across devices, with conflict capture and one-click repair. The mobile companion for Android and iOS is available on Google Play and the App Store.
Bring your collections
Import Postman collections and environments with full round-trip fidelity, plus Insomnia, Bruno, OpenAPI 3 and cURL. Export back to Postman formats any time.
AI that respects secrets
With a Pro AI seat, explain responses and errors, generate requests, tests, mocks and docs. Secrets are redacted deterministically before anything leaves your machine.
Give your team an API to build against
With Echo Pro or Pro AI, publish a mock at a public HTTP URL. Frontends and integrations can keep moving while the real API is still in progress, without depending on your desktop.
Catch contract changes early
Publish versioned API contracts, bind applications to the versions they use, and compare changes for consumers and producers to see possible breaking changes before you ship.
Echo in your .NET apps
Take the work beyond the desktop. Four NuGet packages bring Echo mock rules and contracts into your .NET apps. Scoped application keys connect each integration to the rules or contracts it needs.
- Gapfy.Echo.Contracts publishes versions of contracts your app provides.
- Gapfy.Echo.Testing checks the contracts it consumes against saved snapshots.
- Gapfy.Echo.Mock.Client intercepts selected outgoing HTTP calls.
- Gapfy.Echo.Mock.Server answers unfinished routes in your ASP.NET Core API.
From solo debugging to team workflows
Echo starts as a fast local tool and grows with you. Sign in when you are ready to share, and keep full control of your data the whole way.
Share collections, keep control
Share a collection at Read, Contribute or Full Access, picked per person with in-app people search. Everyone works from the same source of truth.
Keep building before the API is ready
Bring Echo mock rules into your .NET app. Selected outgoing calls and unfinished API routes can get useful answers while the real service is still taking shape.
Local first, never hostage
Guest mode needs no account and never limits the local loop. Your data lives in an encrypted local database, and you can export to Postman formats any time.
Documentation
Step-by-step guides for getting started, organizing your work, and going deep on every feature.
Free, Pro and Pro AI
Start free to test APIs locally. Pro adds hosted mocks, higher limits and team controls; Pro AI adds the assistant that writes tests and explains failures.
Test your APIs the way they deserve
Echo is ready to download today. Bring clarity to your API work and let every request come back loud and clear.
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