Guillaume Rozier, 24, created covidtracker.fr, which is used by news outlets all over the country.
He told The Connexion he never expected all the attention he has received.
He came up with his idea in early March last year before the first lockdown. “No one was really talking about Covid-19 at that time,” he said.
“I decided to do something quite simple.
“Using data provided by Johns Hopkins University in the US, I made a graphic comparing the number of Covid-19 cases in Italy and France at the time. I realised that there was exactly the same progression in both, but France was around seven or eight days behind. That shocked me a little.
“I shared this graphic with my friends and family and put it on Twitter and people seemed interested.
“In the following days, they asked me for an updated graph. I did that every day for a bit but it got annoying so after a while I decided to create a website and put the graph there.”
He estimates that, by January, there had been more than a million unique visitors.
There are now six people working on the website, doing it in their own time free of charge, as does Mr Rozier.
He says it is a public tool and he has no plans to sell the website or make money from it.
He launched a new service called VaccinTracker at the end of December, which can be found through the website.
At first, Mr Rozier had to search through local media outlets to find data as the government did not provide vaccination numbers publicly.
This resulted in the government contacting him to offer him official data that he could then publish on his website.
A few days later, at the beginning of January, he received a call from Health Minister Olivier Véran to congratulate him on his work.
The government began to publish its own vaccination data on January 11.
All the data displayed on covidtracker.fr is official and available publicly via government websites, although not usually in such an easy-to-digest manner.
Mr Rozier said: “My employer is very understanding. He sees CovidTracker as a public service so he is flexible with my hours and doesn’t mind if I take time out during the day to do interviews, or whatever.”
He said his day-to-day life has changed since the website became popular. “I speak to the media a lot,” he said. “Since September, there probably hasn’t been a single week that I haven’t spoken to a journalist.