That the frontend is hosted on someone else's server is a convenience, but I see your point and agree. Technically nothing is uploaded anywhere, nor does it call any APIs to do the de/encryption. Instead, it uses the cryptography mechanisms built into your browser. Local file access and creation are via FileSystem api[0]. Said differently, you could save the page to your desktop—ensure all the includes are to local files, and still run it. In fact, thats's what I did with Portable Secret[1] which others noted was previously posted here. I can confirm this works and nothing "calls home".

[0] https://developer.mozilla.org/en-US/docs/Web/API/FileSystem [1] https://mprimi.github.io/portable-secret

That project and the parent do exactly what you wish:

- run encryption locally

- do not upload anything

You may not realize that’s the case because it’s a web form

> Why is everybody forcing me to upload to the web the very files I want to keep private to myself?

This isn't the use-case I had in mind.

My personal one: I want to build a small utility web app for a very specific task, and it would be used by me and by some of my friends (less than 10 users total). The entire thing can easily be front-end code, which is nice, because I can just host it on Netlify and not bother with hosting, managing it, etc., thus making the complexity of it all much lower.

But there is one catch - the web app uses an external API, and, along with it, the API access key. This puts a big stop sign for making it front-end only. And I don't want to up the level of complexity by managing the back-end just for the API access key retrieval (for a webapp used by less than 10 people). Exposing the API key in the front-end code on a publicly accessible website is one of the worst ideas I can think of.

I haven't done the evaluation on how well the solution in the OP would serve my specific purpose, but it looks promising.