What's the purpose of "This page is intentionally left blank" we see in books?

What's the purpose of "This page is intentionally left blank" we see in books? Why not just leave the page blank and write nothing on it?

I'm voting to close this question as off-topic because it has nothing to do with UX but is a question about the history of book printing.

@VitalyMijiritsky A blank page could have a very specific intention. We use white spaces all the time on screens. Besides, UX is not just digital.

A paradoxically printed page in a book stating that itself is left blank on purpose is a little more on the UX side than "every manufactured object in the world has a user. ", but that's my 2 cents.

9 Answers 9

Such pages may serve purposes ranging from place-holding to space-filling and content separation.

And the reason I see it most often

Intentionally blank pages are usually the result of printing conventions and techniques. Book pages are often printed on large sheets because of technical and financial considerations. Thus, a group of 8, 16, or 32 consecutive pages will be printed on a single sheet in such a way that when the sheet is mechanically folded and cut, the pages will be in the correct order for binding.

And to add to why they write "This page is intentionally left blank" instead of just leaving it blank

They are marked "intentionally left blank", of course, because they don't want readers to worry that a printing mistake has left them missing something good. http://www.quora.com/Why-do-books-sometimes-have-pages-marked-This-page-intentionally-left-blank

As far as I can tell the actual blank page is to account for technical issues/convenience but the phrase "This page is intentionally left blank" itself is for the user to not get confused about the blank page.

It relates to UX in the same way we say "0 search results found" instead of just leaving the page blank.

@Brian: No, they won't keep staring at the page. But they might feel annoyed that they've been sold a defective product, and contact the bookseller/printer and complain. Or (in an examination context) they may panic and believe their exam paper is missing some questions, forcing them to speak to the invigilator/proctor and disrupt the concentration of other examinees (this is the context I've most often encountered "intentionally left blank"!)

I once found 5 consecutive missing pages in the last chapter of a really good novel. I now scan books for blank pages before I read them. These notices help a lot.

You don't see it in all books. You sometimes see it--usually in books that are more academic or legal in nature.

Essentially, it's nice to have in a publication where a user might expect there to be content on that page. A standardized test, or a legal contract are examples where every page needs to be accounted for--even the blank ones that are there.

I only know that phrase from ISO standards. It makes sense to notify the user that there is no important content on the page. Missing pages in an standard you have to conform to would be very bad. "We fully conform to ISO 1337 with this product. " "But whats about xyz on page 6?" "Whoops, seems we don't have the page about not allowing cleaning robots to kill innocent people, bad luck!" wouldn't be very appropriate.

If you might accidentally leave the page blank, you might accidentally insert a page This page left intentionally blank where a proper page should be (for example, a misfeed in a collating machine). A better way of expressing a blank page would be to have the page number and document title in the header/footer as usual, which in itself confirms that the page has not simply skipped the printing process.

There are any number of renderer/printer errors that would correctly display header/footer but would not display body content.

It is very useful with single sheets being printed on both sides, where you want to be able to update the sheets.

You would have pages 1+2 printed on one sheet, pages 3+4 on one sheet, and so on. If you made a change and a chapter changed from 12 to 13 pages, all the following pages would need to be reprinted as well. Instead if you want to insert a single page, you either use an empty page, or you insert a whole sheet with the printed text on one side and an empty page on the other,

Yeah, I've had to do this 2-3 times a year with massive (1000+ page) books of regulations and procedures, that are constantly revised and where page numbers are critical, cross-referenced, and logged. Lots of "intentionally blank" pages, strategically placed, means we can change 1 or 2 sheets, here and there, rather than the whole (bleeping) document!

@DewiMorgan I used to do consulting work for the Air Force. Their old practice was that if a sheet had to be added between the sheet with pages 1 and 2 and the sheet with pages 3 and 4, that the inserted sheet would be labeled 2a/2b. If you needed to insert between 2a/2b and 2c/2d, it was 2b1/2b2. The newer rule is to use decimal. the sheet between 1/2 and 3/4 is 2.1/2.2. If you need a sheet between 2.1/2.2 and 2.3/2.4, it's 2.2.1/2.2.2. Etc.

Interesting! What happens when they reprint it? Do they retain the 23.2.1 numbering in the new printing, or do they break all page references in other materials? I guess if they include the updates, then that's another "edition", and external references should include the edition number, and nobody expects the page number to remain the same between editions?

Printing sheets are done with 8 or 16 pages. This arrangement is much more important in offset printing. If there is any added or deleted context, pages shall be re-organized. Extra empty pages may be added for keeping the same production line.

For not confusing the end user, these empty pages carry that message instead of just being empty.

This talks about blank pages, but the question is asking about the statement "this page left intentionally blank" that is sometimes printed o them.

I didn't think it was anything to do with publishing issues. I thought it was the US Dept of Defense wanting to the distinction between a deliberate blank page and an accidental blank page very clear because an accidental blank page might mean vital information is missing.

@LightnessRacesinOrbit Obviously, if there's something that has happened, but no one claims responsibility, the instigating organization must be the US Dept. of Defense! :P

It can have another explanation for this:

Most people read books from left to right
~> the page which is needed to turn is on the right
~> when scrolling a book, the right page is easier to see
~> title of a new chapter should be on this page
~> if the previous chapter has its last page on the right too, there will need a blank page before starting a new chapter

See recto and verso in Wikipedia

Especially in ebooks it is a nice way to let the reader know that he/she isn't missing something, there is nothing wrong, the blankness of the page really is intentional.

Some kinds of work are printed "as a unit"; before a group of pages is printed, the number of pages preceding it will be known. If a particular printing press is set up to print groups of 24 pages and there are 202 pages before the first page of Chapter 12, then the group containing the first page of Chapter 12 will also contain ten pages from the previous chapter. If that preceding chapter had ended on an odd-numbered page, the publisher may have decided for purposes of appearance to add one blank page (so as to pad the total number of preceding pages to an even number, and meaning there would only be nine pages of content from the previous chapter) but there would never be a need for more than one blank page. Further, if the publisher adjusts page boundaries to avoid having a chapter end with a precisely-filled page, a reader will clearly recognize that the end of one chapter has been reached, see the start of the next chapter on the page facing the blank page, and never have reason to believe--even for a moment--that anything was wrong with the book.

Some other kinds of work are not printed as a unit, however, but instead have different sections printed at different times. For things like unbound newspapers, there's no need to know now many pages will be in the first section before printing later sections (on most newspapers, the first section of the paper is actually the last one printed, and later editions of the paper will combine later-printed first sections with earlier-printed inside sections), but for some kinds of bound publications it may be necessary that sections which are swapped out be replaced with others containing exactly the same number of pages. If a section which had been allocated 48 pages ends up having only 27 pages of content, it may be followed by twenty-one blank pages. Someone who encountered 21 blank pages might quite reasonably be concerned about whether there was a printing problem; marking that the pages were deliberately left blank would serve to allay that fear.

Note that in many cases where there were never two or more blank pages consecutively, readers probably wouldn't care if none of them were marked, but readers may care if some blank pages are marked and some aren't, or if there were any large runs of blank pages that weren't marked. If the first section printed ends one page short of its allotment, the printer may have no way of knowing whether later-printed sections will end with large runs of blank pages. Since the first page of that section will need to be marked if it becomes necessary to mark blank pages elsewhere, it's simplest for the publisher to mark it preemptively.