Hedera consensus nodes use gRPC for communications between nodes. Web browsers have technical and security limitations that prevent direct use of standard gRPC. gRPC-Web enables browser-based applications to call gRPC services with familiar web protocols. In this article, we explore what gRPC-Web proxies are, why they are used in the Hiero JS SDK, the role they play in enabling browser-based Hedera applications, and how gRPC-Web proxies are supported by the network.
What Are gRPC-Web Proxies?
gRPC is a high-performance protocol that uses HTTP/2 and protocol buffers. However, browsers have technical and security limitations that prevent direct use of standard gRPC. gRPC-Web was created to let browser apps call gRPC services with familiar web protocols.
A gRPC-Web proxy is a lightweight server between the browser and the gRPC backend. Its job is to convert the browser’s HTTP-based requests into native gRPC calls and vice versa. The browser sends regular HTTP/1.1 or HTTP/2 requests with special content types (e.g. application/grpc-web+proto), and the gRPC-Web proxy translates those into the binary gRPC format understood by the backend service, then relays the response back in a format the browser can handle. In essence, the proxy acts as a bridge that enables gRPC communication over standard web protocols.
Without a gRPC-Web proxy, a web application wouldn’t be able to directly talk to a gRPC service running on a server. The proxy handles necessary tasks like HTTP to HTTP/2 conversion, managing binary Protobuf messages over text-based protocols, and satisfying browser security requirements (such as CORS and TLS).
gRPC-Web Proxies in the Hiero JS SDK
The Hedera consensus nodes use gRPC APIs, which work well in backend environments (like Node.js servers). However, browsers restrict a direct connection to Hedera nodes for front-end web applications due to security sandbox rules. These rules block low-level gRPC streams and enforce using TLS and approved domains, so a dApp running in Chrome or Firefox simply cannot open a raw gRPC connection to a Hedera node.
Developers building on Hedera need a way to call native APIs that use gRPC without running into these restrictions. To enable this, the Hiero JavaScript SDK (formerly Hedera JS SDK) provides built-in support for gRPC-Web proxies. The goal is to make the proxy layer transparent to developers. When the SDK is used in a browser context, it automatically routes all network calls through a gRPC-Web proxy endpoint instead of trying to contact the node directly.
By bundling proxy support directly into the SDK, Hedera enables web developers to start building dApps without needing to deploy any additional infrastructure. You don’t have to know all the details of gRPC-Web or host your own proxy just to get started.
See the proxy information in the JavaScript SDK for the different Hedera environments.
gRPC-Web Proxies for Web-Based dApps
In practice, every interaction, like creating accounts, querying balances, or submitting transactions, goes through a proxy when using the Hiero JS SDK in a browser. The SDK automatically routes these calls through the proxy, which converts browser requests into standard gRPC calls and then back to a browser-friendly format. This setup meets browser security rules and simplifies development.
The primary benefit of the proxy system is quick and easy connectivity to the Hedera network from web apps. For those developers who want more control in their applications, the SDK allows configuring a custom network or proxy addresses.
The Hedera Address Book Includes gRPC-Web Proxies
With the implementation of HIP-1046 in August 2025, the Hedera address book now includes gRPC-Web endpoint information. The Hiero JS SDK can automatically discover and utilize the gRPC-Web endpoint information in browser contexts. This removes the need for hard-coded proxy URLs and eliminates manual coordination if endpoints change over time.
Here’s how you can take advantage of this:
- Upgrade the SDK to the latest Hiero JS SDK to enable dynamic endpoint discovery out of the box. The SDK will pick up the right gRPC-Web endpoint from the address book when running in the browser.
- If your app or tooling previously maintained a static list of proxy URLs, switch to using the network’s address book (via mirror node) as the source of truth going forward.
Closing Thoughts
We covered gRPC-Web proxies, what they enable, and their role on the Hedera network. These proxies have enabled easy and robust connectivity and access for browser-based applications on Hedera. Additionally, enhancements such as native gRPC-Web support in the address book make it even easier for apps to communicate directly with consensus nodes.
Now that you know about gRPC, gRPC-Web, and proxies, it’s time for you to build your next project on Hedera. The Developer Playground is a great place to start. Be sure to also join our growing community on Discord to share ideas, get support, and help build the future. #HelloFuture
