The WICG has a set of standard proposals called WebPackage, with the goal to make it easier to save and share websites offline.
Per the repository:
[These specifications] will allow people to bundle together the resources that make up a website, so they can be shared offline, either with or without a proof that they came from the original website.
One of the standards is Web Bundles, and I’m excited about this because it looks like it will solve some of the annoyances with web apps and archiving, by storing everything in a single, portable file.
Many web apps have come and gone over the years, as domains expired and their developers moved on. Sometimes they make the source code available, but using the app means getting the entire chain working, from development dependencies to running a web server on your computer.
If these web apps also supported Web Bundles, you could save the bundle file to your computer, always ready to open in your web browser.
Web Bundles could also lower server load and costs. With most of the resources for your app stored locally on your user’s computers, all you would have to host is the initial app download and updates.
Third-party APIs would still be a problem, though. I think the best offline use cases would be documentation, small utilities, or games. There’s tons of little web development utilities that would work well as a Web Bundle, like gradient generators and shadow editors. Web.dev has a few demos, including the entire web.dev site, a Minesweeper clone, and the Squoosh image optimization tool.
Web Bundles are still in draft and there’s no estimate on when they would become more widely available, because the standard needs more work. Chromium 80+ includes support behind a flag, so if you use a Chromium-based browser like Edge, you can play around with Bundles today.