Rather off-topic question: aren't WebExtensions meant to work on all browsers? I don't see either Chrome extensions working with Firefox 57 or the reverse.

Some WebExtensions will work in all browsers. Other WebExtensions will only work in certain browsers that offer a capability that the extension needs. Kind of like webstandards have always worked.

For example, Opera and Firefox support the Sidebar API, which allows essentially arbitrary HTML pages to be placed in, you guessed it, a sidebar. Chrome does not support this, because they supposedly just don't want to have sidebars in their browser (it's not exactly an unsolvable task to implement).

Overall, Firefox will support the most extension APIs, but even there not all extensions will work, because there's always going to be some APIs that only make sense in one specific browser.

Lastly, it is necessary for the extension authors to port their extension. The work they have to do for porting might often be as minimal as just repackaging, testing and then uploading to the other browser's extension webpage, but they do have to do it.

So, this is going to cut off many extensions, too. If they're unmaintained, no one's going to port them. And Mozilla has much stricter policies for telemetry, ads etc. in extensions, too, so another chunk of extensions won't get ported for that reason.

If there is a specific Chrome extensions that you care for getting ported and it's unmaintained, then you can try it with Chrome Store Foxified [1], which will do the repackaging automatically. The testing you'll have to do yourself and then the fixing of potentially broken things and uploading, that depends on the license of the extension, if you're allowed to do that.

[1] https://addons.mozilla.org/en-US/firefox/addon/chrome-store-...

Firefox and Chromium will never support full keybinding-driven navigation. WebExtensions severely limits when keys can be captured, so there are many cases where they cannot be used: when the addressbar is focused, while pages are loading, etc.

Qutebrowser keybindings essentially have full control over the page at all times.

FWIW some people from the Tridactyl project are working with Mozilla at getting a better keyboard WebExtension API for Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=1215061

It's going quite slow however...

as I understand it webextensions are aiming to be a superset of chrome extensions.

WebExtensions are a common extension format/API, i.e. Chrome extensions are WebExtensions.

However, each browser vendor has their own specific additions, and hopefully Mozilla will add some things addons like Vimperator would need, see e.g. https://bugzilla.mozilla.org/show_bug.cgi?id=1215061

Shouldn't be a problem here, as QtWebEngine is Chromium.