Is there any tool to verify client-side website code you get served is the same as the open source version?

There are lots of useful End to end encrypted webapps such as [Protonmail](https://github.com/ProtonMail/WebClients), [cryptpad](https://github.com/xwiki-labs/cryptpad), [cryptee](https://github.com/cryptee/web-client) and many others. And part of why we trust them is that the client side code is open source, so we can see that end to end encryption is really going on and is really secure. Its impossible to verify what code they are running in their server, but if the data we send them is already encrypted we can rest easy.

But one concern …

client client-side code open source privacy tool verify version website