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Why Is My File Size So Huge?

Ben wrote:

I have a 60+ page CS3 file that saves at around 450MB and growing. Doing a quick preflight check shows that there are no embedded images nor saved image previews. The linked photos themselves are high resolution, around 2-3MB a piece. If it’s not saving any image data and merely linking 500 .jpg images, why would this file be so large?

Ironically, I know the answer to this one because of my long history with QuarkXPress, which also exhibits this curious phenomenon. There are a number of things that can make your InDesign files huge. The first thing to always try when trying to reduce file size is to choose File > Save As. That clears out any gunk that has accumulated while you’ve been working on the file.

However, in this case, the problem is, in fact, your images. These images were probably saved from a digital camera to disk, and then imported directly into InDesign. Unfortunately, many cameras save their files at 72 ppi (pixels per inch, sometimes called dpi). It may be a 17 MB, 3000 x 2000 digital capture, but if it’s saved at 72 ppi, then it’s about 41 by 27 inches large. So you import it into InDesign and scale it down to the proper size, which increases its effective resolution (watch the Info palette to see original vs. effective ppi).

Now here’s the rub: When you import an image, InDesign saves a low-res “thumbnail” preview of it, right? That’s what’s stored in the InDesign file itself (so you can still see the image if the original on-disc image is missing). But when you import a 72 ppi image, InDesign saves the entire image as the preview! It essentially embeds the whole thing because it’s trying to save a low res (72 ppi) version of your 72 ppi image.

The solution: Open your file in Photoshop, choose Image > Image Size, turn off the Resample Image checkbox (if you don’t want the image data to change), then set the resolution to something reasonable (such as 225 or 250 ppi). Now save the file and reimport it into InDesign. InDesign places the image at the proper size, makes a much smaller proxy image, and the next time you do a Save As, your file size should drop considerably.
Sure, there are other reasons that InDesign files can get huge, but images are the main problem I’ve encountered.

(By the way, I discovered why InDesign files jumped in size between CS and CS2: Color management was turned on by default in CS2 and InDesign started embedding CMYK profiles in its files. A CMYK profile may be 1-2Mb in size, so the minimum InDesign file size–what you’d get if you just had an empty INDD file–suddenly got much bigger.)

By the way, Ben later replied:

A quick batch in Photoshop helped me to fix these up to about 180dpi at no larger than 8 inches in either horizontal or vertical.  The file size wasn’t decreasing until as you suggested doing a simple Save as.  Sometimes it’s the slightest things that can trip you up.

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Comments

59 Comments on “Why Is My File Size So Huge?

  1. Amazing what a simple trick like this can do. I couldn’t understand how our parish bulletin, normally saving at ~90MB, suddenly jumped to 206MB two weeks ago. After reading this, I found the single errant .jpg, and once it had been replaced by a more reasonably-sized version, the file dropped from 206MB to 53MB.

    Now I’m considering mustering the energy to re-visit all those older .indd files, to re-claim some valuable disk space.

    Thank you so much for this tip.

  2. I had a file that was 27 MB big. I made some corrections, and it ballooned out to 2.89GB. Huge file. None of the above helped. Someone somewhere else suggested I save it as a .idml file. Then re-open.

    Once I’d resaved it as an indesign file, it was down to 14 MB!!

    It might have had something to do with fonts. A font missing dialogue box appeared immediately on saving the new file.

    Problem is now fixed – tho i have no idea how or why this happened…

    • This worked so well for me. 2 page indd coming in at 1.92GB?! When I did the idml trick, it dropped it to 3.3MB and got rid of some little corruption in there or something. I didn’t get any font problems though.

  3. I work on a monthly magazine which usually ends up being about 5mb. Last month there were a number of graphics in the magazine, jumping the size up to 60mb. I use the previous month’s magazine as a template for the next month, deleting all of the old articles. This month, after deleting all of the articles and graphics from the previous month, the file size was still 60 mb. There was no sign of any graphics anywhere in the file, so was mystified as to why the file was still so large. I tried what was mentioned in this forum, of doing another “save as” of the current file, and it worked. The file size is now down to 5mb. I’m not sure I understand why this worked, but I am thankful it did. Thanks for the help!

    • Ron: no, PDF file size is usually controlled in the pdf export dialog box. PDF file size often has nothing to do with INDD file size because it involves image sizes, compression, etc.

  4. I have kind of a different, but related question. Sometimes, I export a file from InDesign as a PDF Low Resolution. Then , when ready to print, I export a High Resolution version of the same file.

    Why is it that sometimes the Low Resolution PDF ends up being a larger file size than the High Resolution PDF?

    It makes no sense.

    MW

    • Melissa: That’s a fascinating question, but there is one way in which it actually does make sense. High-resolution really means “high quality” in that InDesign tries to maintain everything as vectors as much as possible. Low-resolution will convert more to raster (bitmapped) images. Raster often will take more space (file size) than vector.

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