I am in the team who builds an eReader which supports Reflowable books and books are in ePub format.
When I launch the Reflowable book the page count is dynamic in nature.

For Example:
Given I have book that has 100 pages on default 100% screen size
When I zoom in to 200 percent, the page count increases to 200 pages
When I zoom out the screen to 50 percent the page count decreases to 50 pages

In this scenario how can a user bookmark the page, because the content always flows in the book. If I bookmark page-2, and I zoom in the page-2 content will be scattered to 3 and 4 pages. I am not sure how a user can bookmark pages. Hope the answer works across all the zoom in-out percentages.

4 Answers 4


You could add a highlight text function then once the user highlights the text they have the option to bookmark the text.

That way regardless of how zoomed in/out they are, they are still able to get back to the right spot and continue reading merrily.

The blogging webpage Medium does this in quite a nice way:

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  • 1
    @Pri I would suggest testing this method. Especially for the discoverability of such a feature and if it is intuitive for the user to do it this way. Mar 12, 2018 at 10:34
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    Yeah, we have this feature already that we term as Annotations. I believe Reflow book user uses mostly Annotation feature, rather than bookmark
    – A user
    Mar 12, 2018 at 11:09

Rob E's excellent answer covers the case where the application can (and the user wants to) mark specific passages of text.

If you also have (or want to offer) a simple "bookmark this page" option, without the user needing to mark a specific passage, then I think you should store the "location" of the paragraph at the top of the current page. When returning to the bookmark, display the stored location at the top of the new page.

My first instinct was to suggest storing the location that's closest to the middle of the current page (with the reasoning that if you put that bit of text in the middle of the page when you return to a bookmark you would be "reasonably close" to where the reader wanted to be, most of the time, for most zoom levels).

However, as an avid Kindle user, I thought about when I use the bookmark function as opposed to highlighting a passage of text:

  • If a work of fiction has a map of the area where the action takes place, I'll often bookmark that page so I can return to it easily if I need to check the geography.

  • If there is some kind of glossary, list of characters, ... list of almost anything, I again might bookmark the first page of such a list so I can return to it easily.

The common thing is that the thing I'm marking is usually either the only thing on the page (very often the case with maps) and/or forcibly starts a new page (usually the case with glossary or similar). In both cases, going back to the beginning of the page originally marked seems to be the correct thing to do.

Also, as Monty Harder pointed out in a comment, when using a bookmark for its "traditional" purpose – going back to where you left off reading – then bringing the text that used to be at the top of the page back to the top of the page (even if the zoom-level is different) is the safest option: at worst, you might have to skim over some parts you've already read. However, if you brought what was in the middle of the page back to the middle, there is a chance (if the zoom-level has increased) that unread portions of the text have been pushed back on to the preceding page.

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    This has the advantage that if I'm returned to the top of the page where I left off reading, I can quickly locate the exact spot where I left off, but if you try to bring up what was at the middle last time, I might miss a few lines that flowed onto the previous page. Mar 12, 2018 at 22:29
  • This is also a good work around. Mar 13, 2018 at 8:54

When bookmarking my place in a physical book, unless it's a chapter boundary or similar, I always place the bottom of the bookmark on the specific line where I want to resume. Bookmarking ebooks, whether reflowable or not, should work the same way - you don't bookmark a page but a specific point in the text.

  • "Bookmarking ebooks, [...] should work the same way" The "problem" is that with all eBook interfaces I've seen, you either bookmark a (whole) page, or highlight a portion of text. You could add a paragraph/line/character-level bookmark function – but then you'd have three ways of marking, which could be cumbersome; you could change the bookmark function to operate at para/line/char level, but that would require extra "fiddling" if you only want to mark the page. While not perfect, I think I'd stick with bookmark page; highlight/annotate specific position.
    – TripeHound
    Mar 13, 2018 at 8:44

The Document Object Model (DOM) structure of the document might be useful here: While the display reflows, the underlying markup of the EPUB ought to remain the same, so a bookmark could be a reference to a node in the document.

The brute-force way to do this would be to give every paragraph, for example, a unique ID based on chapter and paragraph number. Alternatively, you might find it better to store a bookmark based on the DOM alone - that's what a computer recognises.

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