Privacy
Last changed 30 August 2026.
There is no account, no email address, no password and no sign-up. We
do not know who you are, and the page is built so that we cannot find
out.
What the page keeps on your machine
One random string, in your browser's own storage, made up by the page the
first time you open it. It looks like anon-3f9c21b4. It is not
derived from anything about you or your computer, it is never sent anywhere
except to ask for work and to hand back counts, and nothing is registered
against it.
Also stored: whether you had scanning switched on, so a refresh does not
quietly stop it.
There are no cookies and no third-party scripts of any kind. No analytics,
no trackers, no advertising, no fonts or libraries loaded from anyone else's
server.
What the server keeps
- How far the whole scan has looked, as a small number of ranges. This is
the point of the project.
- A running total against your random ID: how many blocks it has turned
in and how many primes those held. Two numbers, no history — not when, not
from where, not which blocks.
- A count of how many people have contributed, kept as a filter rather
than a list, so the number exists and the roster does not.
- If a block is ever flagged as unusual, that block is written
down in full, including the IDs that scanned it. That is the only way a
finding can be traced back to the person who found it.
Blocks that come back ordinary — which is essentially all of them — are
not stored individually at all. They merge into the record of ground already
covered and the individual result is gone.
Your IP address
Your address reaches our server the same way it reaches every website you
visit, because that is how the internet delivers a reply. We use it for one
thing: a limit on how many blocks a single address can request in an hour, so
nobody can flood the project. That count is held in memory, expires within
the hour, and is never written next to your ID or your results.
The web server also writes ordinary request logs, as web servers do.
What we never do
- Sell, rent, share or hand anything to a third party.
- Attempt to identify you, or to link your ID to your address.
- Profile you, advertise to you, or contact you. We have no way to.
- Run anything on your machine beyond the page you can read in
view-source. It counts prime numbers. That is all it does.
Stopping, and erasing
Close the tab and everything stops immediately. Clearing this site's data
in your browser deletes your ID, and you become a completely new anonymous
volunteer next time — there is nothing to delete on our side, because there
was never anything there tied to you.
Changes
If this ever changes, the date at the top changes with it.