Short version: there are no accounts, no sign-ups, no tracking cookies, and the visitor counter never stores your IP address. The simulations themselves send nothing anywhere — they run entirely in your browser and work with the network switched off.
Every page asks for a one-pixel image at /hit.gif. That request is how the site counts visits. For each one it records:
/light-workgoogle.com, never the full address you came fromsciencesim.orgThe visitor id is not an identifier of you. It is a SHA-256 hash of your IP address, your browser's user-agent string, the date, and a secret known only to this server, cut down to ten characters. Without that secret it cannot be worked back to your address, and it changes every day, so the same visitor on two days looks like two visitors. That is why the statistics count "visitor-days" rather than people.
Visits counted before the site moved to Cloudflare were hashed by the previous host. When those records were copied here, each visitor id was hashed again, with the date and a separate secret that is not kept on the server, so those ids cannot be worked back to an address either.
The counter skips requests that identify themselves as bots. If your browser blocks the request, nothing is recorded and nothing else is tried in its place. If the server’s secret is ever missing or too short, it records nothing rather than fall back to a weaker hash.
This site carries no advertising, and no advertising code of any kind runs on it. Nothing on these pages is loaded from an ad network. If that ever changes, this page will say so before it happens, and visitors in the UK, the EEA and Switzerland will be asked for consent first, as those rules require.
The site is hosted on Cloudflare: the pages and the visitor counter are served by Cloudflare Workers, and the films are stored in Cloudflare R2. Like any web host, Cloudflare receives your IP address and the ordinary details of each request (the page asked for, your browser’s user-agent string, the time) in order to deliver the page, and it supplies the coarse country and city described above. The records Cloudflare keeps of these requests are covered by its privacy policy. Cloudflare’s documentation says its dashboard shows me traffic totals and, for up to the last seven days on its Free and Pro plans, a sample of individual requests (every request, when there are only a few), including their IP addresses. I do not export those records or combine them with the visitor counter. Cloudflare also offers request logs for the site’s own code (Workers Logs), which would record the details of every request that code handles; they are switched off here.
Cloudflare can add its own analytics, scripts and cookies to the sites it hosts. Those features are switched off here.
The exception is security: if Cloudflare decides a request looks automated, it may show a check page, and passing it sets cookies, among them cf_clearance, which Cloudflare’s documentation says stores proof that the check was passed. Ordinary visits set no cookies.
Cloudflare is a US company. It says it primarily stores data in the United States and the European Economic Area, and it relies on the EU–US Data Privacy Framework and its UK Extension for transfers.
Counter records are kept for as long as the site runs; there is no automatic deletion. They contain no cookies, no addresses and no user-agent strings, so on their own they cannot be traced back to a person. I do not match them against Cloudflare’s request records.
These simulations are built for school classrooms, so many visitors are under 18. Nothing here asks a visitor for information, and nothing here builds a profile of anyone. There is no login, no comment box and no upload. A teacher can put this site on a classroom screen without any pupil data leaving the room.
If you are in the UK or the EEA you have rights of access, correction and erasure over personal data about you. Because the counter’s records hold no name, address or cookie, and I do not match them against Cloudflare’s records, there is in practice nothing here to retrieve or delete on request — but if you believe otherwise, write to me and I will look.
Questions, corrections, or anything on this page that reads wrongly: science.sim1801@gmail.com
If what the site collects changes, this page changes with it, and the date below changes too.
Last updated 23 September 2026 · ScienceSim · sciencesim.org
