Download websites that use Yaws

About Yaws

The problem this web server was written for is the connection that stays open and does almost nothing. Long polling, chat, streaming, telemetry from swarms of small devices: workloads where the count of simultaneous sockets matters more than requests per second, and where a process-per-connection design collapses. Yaws answers that by being written in Erlang, whose lightweight processes and supervision trees were designed for exactly that shape of load in telephone switches, long before the web needed it.

Language choice is what makes this record useful, because it says more about the organization than about the software. Nobody arrives at Erlang by accident. A team running this server has almost certainly made a deliberate engineering decision, usually tied to a real concurrency requirement, and often made by people with a background in telecoms, messaging or financial infrastructure. So a domain in this list works as a filter for a certain kind of technical organization, which is a much harder thing to buy than a list of sites running a common server.

Scale confirms the reading. As of October 2026 the banner appears on 100 sites, which puts the server in the specialist bracket rather than in the same conversation as general purpose web servers. Released under BSD in 2002, the project has had a long time to accumulate whatever adoption it was going to get, and the shape of the installed base looks settled rather than expanding.

Version data adds a second dimension. We see 9 distinct releases across the detected hosts, with 1.90 accounting for a large share of them. A narrow release spread on a server of this age says these are long-lived installations. Somebody set the machine up, the machine did its job, and no reason to touch it again ever arrived. For anyone tracking patch levels, a settled version distribution is both easier to reason about and more worrying, because hosts that never upgrade are hosts still exposed to whatever was fixed in between.

The usual caveat about server detection applies and bites harder here. The signal is a response banner an administrator can suppress, and any host behind a CDN or a reverse proxy will report the proxy instead. Given that a server like this often gets chosen for internal or backend roles rather than for public marketing sites, the visible population is probably a small fraction of the deployed one.

Checking a single domain answers whether that host advertises the server. The downloadable set answers the questions worth asking about a niche technology: which countries and industries cluster around it, which sites pair it with other components from the same language ecosystem, whether the installed base is thinning between snapshots, and which organizations have the kind of engineering culture a specialist recruiter, a consultancy or an infrastructure vendor would want to reach. For a technology this rare, the value is in seeing all of it at once.