I mean, you can be completely sure that the website works offline by unplugging the cable/turning off your wifi connection after it's completely loaded. But that's just a functional test, not something you can expect users to do during a normal browsing session
My initial plan was to replicate the functionality of tools like tinyjpg, thus just offering users a simple interface with good defaults. But I already had in mind the lossy/lossless re-encoding functionality, as well as the quality slider, which I plan to add sometimes in the future
In my (quite small) experience, developing with NextJS has been a breeze.
Some time ago I've decided to rewrite a landing page, written in Node + EJS templates + JQuery, using some kind of static generator. I have always heard good things about NextJS as well as Gatsby, but after some exploration I decided to go with NextJS, since Gatsby seemed more complex and better suited for CMS/other complex websites rather than a simple, light landing page.
The developer experience has been amazing. Plus, I've found an awesome library[0] for dealing with i18n, which completely absorbed the pain of dealing with multiple languages: getting SEO right, make links work, and so on.
Plus, pairing NextJS with PReact, brought my pages first-load size down to ~40KB (external resources excluded), which I didn't think it was possible for something built with React.
The only things that I missed from CRA-like apps were environment variables, which have been added with this release, and a good integration with third-party tools like eslint, typescript and prettier. I did not use typescript because it was just overkill for a simple landing, and I'm launching eslint by hand and in the CI, so I really miss how good the integration is when developing a normal React App bootstrapped with CRA (which has all of this awesomeness out of the box).
I mean, you can be completely sure that the website works offline by unplugging the cable/turning off your wifi connection after it's completely loaded. But that's just a functional test, not something you can expect users to do during a normal browsing session