Durable Streams introduces a new HTTP-based protocol designed for real-time data streaming to client applications. It aims to provide reliable, ordered, and replayable data streams that can be resumed from arbitrary points. This is particularly useful for modern applications that require consistent data flow, such as AI chatbots, collaborative editing tools, and real-time database synchronization. Unlike traditional solutions like WebSockets or Server-Sent Events, which can fail during network interruptions, Durable Streams ensures users can pick up right where they left off after disruptions. The protocol has been successfully used in production at Electric for over a year and a half, handling millions of state changes daily for real-time Postgres synchronization. Key features include refresh-safe connections, shareable stream URLs, and seamless operation across multiple devices and tabs. It also supports high fan-out, which means a single origin can handle millions of concurrent viewers efficiently. Developers can easily integrate Durable Streams into their projects using the npm packages for various languages, including TypeScript, Python, Go, and Java. The protocol is designed to be simple, leveraging existing HTTP standards without the need for custom protocols. It offers features like real-time updates with long-polling, offset-based resumability, and flexible content types. Testing and development tools, including a command-line interface and a web-based Test UI, help streamline the implementation process. Overall, Durable Streams fills a significant gap in client-side data streaming, providing a robust solution for developers looking to implement reliable real-time features.