*On first use it can download up to 300MB into your borwser storage, but does it only once.*
The TTS part runs 100% in your browser, so the audio quality is much better on Desktop devices using Safari or Chrome compared to Android and iOS.
https://desktop.with.audio/reader/new?github
It also works for any link as long as the backend can fetch the content.
Check it out and let me know what you think. If you are interested in more details there is also a blog post about this: https://blog.with.audio/posts/web-reader-tts