  Urgent computing workloads are time critical, unpredictable, and highly
dynamic. Whilst efforts are on-going to run these on traditional HPC machines,
another option is to leverage the computing power donated by volunteers.
Volunteer computing, where members of the public donate some of their CPU time
to large scale projects has been popular for many years because it is a
powerful way of delivering compute for specific problems, with the public often
eager to contribute to a good cause with societal benefits. However,
traditional volunteer computing has required user installation of specialist
software which is a barrier to entry, and the development of the software
itself by the projects, even on-top of existing frameworks, is non-trivial.
  As such, the number of users donating CPU time to these volunteer computing
projects has decreased in recent years, and this comes at a time when the
frequency of disasters, often driven by climate change, are rising fast. We
believe that an alternative approach, where visitors to websites donate some of
their CPU time whilst they are browsing, has the potential to address these
issues. However, web-based distributed computing is an immature field and there
are numerous questions that must be answered to fully understand the viability
of leveraging the large scale parallelism that website visitors represent. In
this paper we describe our web-based distributed computing framework, Panther,
and perform in-depth performance experiments for two benchmarks using real
world hardware and real world browsing habits for the first time. By exploring
the performance characteristics of our approach we demonstrate that this is
viable for urgent workloads, but there are numerous caveats, not least the most
appropriate visitor patterns to a website, that must be considered.
