Download websites that use Socket.io

About Socket.io

Real time features leave a trace in the page source, and Socket.io is one of the clearer ones. A site that loads the library is not serving a brochure. Somewhere in the product there is a chat window, a live dashboard, a collaborative editor, a notification tray or a game loop, and the server needs to push data to the browser without waiting to be asked.

Socket.io is a JavaScript library that wraps the WebSocket protocol and falls back to HTTP long polling when a proxy, a corporate network or an old browser refuses the upgrade handshake. The fallback is why the library outlived the arrival of native WebSocket support everywhere. Released in 2010 under the MIT license, Socket.io also ships rooms, namespaces, automatic reconnection and acknowledgement callbacks, all of which a team would otherwise hand roll on top of a raw socket. Server side support centres on Node.js, with client libraries for other languages maintained by the community.

As of October 2026 we detect Socket.io on 15,584 sites. 6,151 of them carry a domain registered in United States, and the suffix mix is weighted to .com. Registration country describes where the operating company sits rather than where its users are, so a list built on this signal reads as a directory of product companies and agencies, not as an audience map.

Persistent connections also constrain the infrastructure underneath a site, which is why the signal carries further than the front end. A server holding open sockets keeps state per visitor, cannot be scaled by a stateless request router alone, and needs sticky sessions or an adapter backed by a shared store once it runs on more than one machine. A site loading the library is therefore a site whose hosting bill grows with concurrent users rather than with page views, and that is a different purchasing profile from the rest of the web.

A per domain lookup answers one question, which is whether a given site runs the library. The downloadable list answers the questions that only a population can answer. Which hosting providers concentrate real time applications. How the library correlates with a particular framework, payment provider or analytics stack. Whether a market you are entering already runs on socket based products or still polls for updates. Vendors selling managed WebSocket infrastructure, observability, load testing and message queues use exactly that cross tabulation to size a segment before contacting anyone inside it.

Detection has limits worth stating plainly. The library is usually identified from the client bundle a site serves or the transport path it opens, and a build step that inlines and renames modules can hide both. Sites behind that kind of bundling go uncounted, so treat the figure as a floor rather than a census. Version information is a second gap. The served bundle rarely announces which release it came from, which is why no release breakdown appears beside Socket.io while other technologies on this site carry one.