MokuToc

Most tables of contents cost you a column of the page, and on a phone they are usually hidden altogether, which is exactly where a reader most needs to know where they are. MokuToc sits at the edge of your content as a row of thin dashes and opens the full list only when someone reaches for it. Below your mobile breakpoint the same component becomes a sticky bar naming the current section. It reads the headings that are already on the page, so there is no second outline to keep in sync when the copy changes.