Long articles are everywhere — documentation, research papers, Substack posts, long-form journalism. And browser tabs are how we "save" them. We pin them. We bookmark them. We email ourselves links. Then we come back hours later, scroll frantically trying to remember where we left off, give up, and close the tab.

I got tired of this workflow and built ReadMark , a Chrome extension that automatically saves your scroll position on any page and restores it when you return. This article covers the technical challenges of building a reliable reading position tracker.

The Core Problem: Scroll Position Is Not a URL

The naive solution is to store window.scrollY per URL.…