Proton Calendar is not Open Source (Mobile)

The code of Proton Calendar is not open-source since a few years (last update was in 2021 : GitHub - ProtonMail/proton-calendar: Proton Calendar built with React. ).

Last year Proton talked about this and they say they were planning to add it to github repository, but still nothing :

As we have no guarentee that Proton Calendar is 100% E2EE (no one can check the code), it is heart breaking for me to suggest to temporarily remove Proton Calendar from PG.

PS : Today is my birthday

Happy birthday. My understanding is that all of Proton’s web-based source code was moved to this combined “monorepo”:


Thank you !

So the web source is available, isn’t it a problem if the source code isn’t available for other devices (Android, iOS…) ?

Instead of removing it, we could maybe add a note next to Proton Calendar’s section to say that the source code is not available yet for other devices (not updated since 2021), if you think it could be important for users to know.


that’s not the calendar app

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This is Proton Mail app, not Calendar app

It is now 2024 and the Proton Calendar mobile apps aren’t opensource and haven’t been since 2021. While web source code is available in their webclient repo this still violates their open source guarantee on their landing page and dedicated open source page.

All our apps are open source and independently audited by security experts so that anyone can use them, inspect them, and trust them.

For over two years now they have been saying they will publish the repo on Github as referenced above by IksNorTen and again 1 year ago and again 3 months ago.

To me this seems very strange if the Proton Calendar mobile app codebases are mature and well-written they should already be well documented. However the fact that they have been unable to do something as simple as publishing the repo after all of this time and that they still represent all of their apps as open source instills distrust.

In summary, I too believe the Proton Calendar recommendation should be revoked, reconsidered or at least caveated in some manner.


Thank you for the rapid response.

Thanks for updating this thread, and thanks @jonah for your quick answer to this issue.

I wish Proton will soon make changes for this problem with Proton Calendar.

Seems to me that Proton has abandoned the open source path, they also haven’t updated their VPN source code for macOS for more than 8 months.
I think the company’s revenue has grown significantly and they have come to the point they don’t really care about privacy anymore.
Anyway I personally don’t trust them, for some reason they seem suspicious to me.

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This is FUD. Stop it.


Maybe, but I think trusting a company is a matter of personal choice, I trust companies who keep their open source code up to date.


Do you have a counter argument? “FUD” can sometimes be quite warranted. Not saying it is the case but screaming “FUD” is the trendy equivalent of calling something a conspiracy theory in order to dismiss it instead of providing a counter argument. If nothing else, people should still be able to express their doubts and concerns, I think


It’s somewhat ironic because the same user claiming FUD was making unsubstantiated claims about Apple oath yesterday. I could no longer find the thread in my comment history.


Quick reminder to everyone about our CoC:

Always attack the argument, never the person.


In this case it’s just someone saying “their source repos haven’t been updated, I find that suspicious!!1!!1!” rather than an actual argument based on that fact alongside others. Calling it FUD is thus warranted here. Not being fully open source is not a sin in of itself, if they refuse to update the sources that are available then we can rehash the whole “they’re suspicious” argument (if the company already has refused to update repos then the point is moot but I haven’t seen anything about that personally)

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Sure, thats besides the point though, point being that FUD can be perfectly legitimate. In other words, by just calling something FUD youre not adding anything to the conversation since that by itself doesnt tell you anything


It tells you that the person accusing another of FUD believes the point being made is, in their eyes, unworthy of even a debunking because its nature as falsehood or exaggeration is so self-evident.

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In what dictionary?

Again, the point, which youve continued to miss, is precisely that some people have taken to just label as “FUD” any criticism they dont like and leave it at that :wink:. The person youre accusing of “FUD” doesnt gain anything from the exchange, nor will anyone else reading it, since that by itself is not an argument, it doesnt present any new or previously unconsidered facts or reasoning


Please avoid dishonest accusations as well as misrepresentations of why this thread exists, which is far from unjustified given what is explained in my first post, assuming you read it.

It doesn’t make sense for me to say so (as my person is irrelevant to this topic) but I’ll make it clear anyway: I’m a long-time Proton user and I use all their products (including Proton Calendar, which no matter what anyone says is much better in terms of privacy and security than most other calendars with synchronization) and that doesn’t stop me from questioning certain aspects of their services, because nothing is perfect. So it’s NOT spitting on Proton to point out to our community, which is all about service transparency, that there’s a grey area forming on this side of Proton Calendar.

If it were a simple matter of a few weeks’ delay in communicating the code, it wouldn’t be a problem, because it’s difficult to always be on time, especially for services of this importance. But in this case, we’re not talking about a few weeks, or a few months, but a few YEARS.

This problem has been going on for almost 5 years now, despite the fact that the Proton team has said it would be solved soon.

Also an other quick reminder of PG fundamental criterias in case you forgot ( privacyguides_org/en/tools/ ) :

If you’re looking for a specific solution to something, these are the hardware and software tools we recommend in a variety of categories. Our recommended privacy tools are primarily chosen based on security features, with additional emphasis on decentralized and open-source tools.