Can I remove android system webview?

I use Firefox as my default browser on my phone. Is it OK if I remove android system webview from my device? Will this break my phone?

Nothing should break. Applications might no longer be able to open the browser without switching apps, but you can install Andoird System WebView again from the PlayStore (example source).

If you want to try removing it, go for it. This is something that you should be able to easily restore.

Just (as always) backup everything important beforehand.