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Mediator
What it is
Mediator is a free desktop GUI proxy for debugging gRPC traffic on Linux, macOS, and Windows. It can direct requests to beta or test servers without requiring changes to client code. When an API schema is available, Mediator parses gRPC requests and responses and can show binary messages as a JSON tree. Schema options include gRPC server reflection, proto source roots compiled with protoc, and FileDescriptorSet files. Mediator can also decode gRPC and HTTPS requests when a server rule matches and the client has installed that installation’s root certificate. Each installation creates a separate certificate, available in DER and PEM formats, so a different installation requires its own certificate to be installed. The proxy listens on port 8888 by default. The project lists Windows MSI, macOS DMG, Apple Silicon macOS DMG, and Linux deb downloads, and includes setup examples for Java, Objective-C/iOS, and Go clients. The project identifies its license as Apache-2.0.
For and against
For
- Runs on Linux, macOS, and Windows
- Redirects requests without client-code changes
- Supports several API schema sources
- Includes Java, iOS, and Go setup examples
Against
- Decoding requires a matching server rule
- HTTPS inspection requires installing its root certificate
- Each installation uses a separate certificate
The verdict
Mediator brings request routing and schema-aware gRPC inspection into a desktop proxy. Certificate setup is an important consideration for HTTPS decoding and when switching installations.
Who it suits
Mediator is for developers configuring gRPC clients who need to inspect traffic or direct requests to test and beta servers.
Plans and prices
Free
Cross-platform GUI gRPC debugging proxy · Apache-2.0 licensed
Read 4 Oct 2026 · github.com
On the record
- Certificate handling
- Each installation generates its own root certificate, available in DER and PEM formats, and a different installation requires reinstalling its certificate.github.com · read 4 Oct 2026
- Client examples
- The README gives proxy setup examples for Java, Objective-C/iOS, and Go clients.github.com · read 4 Oct 2026
- Desktop downloads
- The project lists Windows MSI, macOS DMG, Apple Silicon macOS DMG, and Linux deb distributions.github.com · read 4 Oct 2026
- Desktop framework
- The project says it uses Netty for the proxy protocol, Compose Desktop for the GUI, and Sisyphus as the Protobuf runtime.github.com · read 4 Oct 2026
- Host rewrite
- It can redirect requests to beta or test servers without changing client code.github.com · read 4 Oct 2026
- HTTPS inspection
- It can decode gRPC/HTTPS requests when a server rule matches, using a Mediator root certificate installed in the client.github.com · read 4 Oct 2026
- Intended users
- The repository describes the product as a gRPC debugging proxy and provides setup instructions for developers configuring gRPC clients.github.com · read 4 Oct 2026
- License
- The repository identifies its license as Apache-2.0.github.com · read 4 Oct 2026
- Protobuf decoding
- It parses gRPC request and response messages and can render binary messages as a JSON tree when an API schema is available.github.com · read 4 Oct 2026
- Proxy default
- When the app opens, its proxy server listens on port 8888 by default.github.com · read 4 Oct 2026
- Purpose
- Mediator is a cross-platform GUI proxy for debugging gRPC traffic.github.com · read 4 Oct 2026
- Schema sources
- Mediator supports gRPC server reflection, proto source roots compiled with protoc, and FileDescriptorSet files as API schema sources.github.com · read 4 Oct 2026
