How to implement password save?

I’m working on some scenes for a playtest and I’d like to know how to implement a password save system so that playtesters don’t have to restart all over from the beginning whenever they get back onto the browser. That and if they refresh, then the story doesn’t load all over again. Please help?

So far I have a soft save system set up, but as I add more chapters, it might get more frustrating to lose all that story data.