From an article by Ramces Red published in the maketecheasier web site

(Note: This article describes a program that runs only on Linux computers.):

Archive your favorite websites today!

Archivebox is an easy-to-use Linux archival program that allows you to create an accurate snapshot of any website. This can be helpful for archivists and users that want to preserve information online. Not only that, Archivebox is also incredibly simple and easy to use. For example, you can run the program both as a command line tool and as a web app that you can access anywhere.

Why Should You Archive Websites?

Over the years, the World Wide Web enabled individuals across the globe to easily share and communicate information with each other. One issue with the Web, however, is that websites do not hold up over time.

Most websites only stay active for around two to five years. After that, they either go offline completely or are replaced by a different website altogether. For example, there are little to no websites from the 1990s that are still online today.

Alternatively, you can also use the WayBack machine to archive websites – no installation required.