Curl 8.21.0 Adds WebSocket Support for Real-Time Data Transfer 🔗
New WS/WSS protocol handling expands curl’s reach into live-streaming and IoT applications
The latest release of curl, version 8.21.
0, introduces native support for WebSocket (WS) and Secure WebSocket (WSS) protocols, enabling direct real-time data transfer from the command line. This update allows developers to test, debug, and interact with WebSocket servers using familiar curl syntax—such as curl ws://example.com/socket—without relying on external tools or custom scripts. Built on libcurl’s robust transfer engine, the feature handles framing, masking, and pings automatically, aligning with RFC 6455.
This enhancement strengthens curl’s position as a universal data transfer tool, already supporting over 20 protocols including HTTP, MQTT, SFTP, and SMB. For developers working with live dashboards, financial tickers, or IoT telemetry, curl now offers a lightweight, scriptable way to subscribe to WebSocket endpoints and inspect payloads in real time. The release also includes performance improvements in HTTP/3 handling and updated CA certificate bundles.
Despite its breadth, curl remains a C-based tool with a steep learning curve for advanced options. Its monolithic design prioritizes portability and protocol completeness over modularity, which can complicate embedding in memory-constrained or security-sensitive environments.
The catch: WebSocket support in curl does not yet include per-message compression extensions or subprotocol negotiation, limiting compatibility with some optimized WebSocket services.
Why this leads today curl/curl’s pervasive use in developer workflows means its ongoing stability and incremental improvements directly enhance the reliability of networked operations across the software ecosystem.
- Debug WebSocket APIs directly from terminal
- Test IoT device telemetry over WS/WSS
- Monitor live financial data streams via command line
Source: curl/curl — based on the README and release notes.