50+ MB mobi file upload to Kindle App on iPad

So, I’ve been trying to find a way to upload a just-over-50MB .mobi file to my Kindle library for the past few days. It was not bought through Amazon, but another eBook service. The limit for using the “Transfer To Kindle” app on either Windows or iPad is 50 MB, so that won’t do it.

I was able to transfer it to my Kindle reader (a PaperWhite) by connecting it to my PC via USB and simply copying the file. Worked great! I’m going to try the same method with my iPad running the Kindle app, but I suspect it won’t work - or will it? My attempt will have to wait until the lightning-to-USB cable I ordered from Amazon arrives tomorrow. (The cable I use for charging the iPad is unconnectable from the wall - don’t ask :-))

Googling has revealed numerous sites claiming you can use DropBox or various other cloud services to get around the 50 MB limit of Transfer To Kindle, but no matter how I try, the Transfer To Kindle “feature” of the Kindle app on my iPad always manages to get in the way and prohibit it.

Anyone have any ideas?

The cable should fix it.

Otherwise, try ResilioSync.

I’ll also say that someone had to put in some extra effort to enforce that 50M limit… and I have no clue why they might have thought it’s a good idea. (And I’m a retired professional computer geek. I HATE arbitrary limits like that, with no reason for existence other than to create more ways for things to go wrong.)


The cable should fix it.

I should know later today, and hopefully I won’t have to install the iTunes monstrosity on my PC to do the actual transfer.

Otherwise, try ResilioSync.

Thanks, I’ll take a look.

I downloaded and installed the free version of “AnyTrans” yesterday, but I’m not sure if it’s truly free to use or will require payment, but it looks pretty capable. See https://www.imobie.com/anytrans/guide.htm

As for the 50 MB limit, yeah, it’s pretty annoying. I can’t imagine there’s some vast library of > 50 MB mobi files out there that Amazon is deliberately trying to exclude, but perhaps there is. Seems more likely that the 50 MB limit was fine 5 years ago, but now needs to be updated. I wonder if there are any kindle books available from Amazon itself that exceed 50 MB.

Finally, my understanding is that I still won’t be able to get my 50 MB mobi file loaded into my online Kindle library and can only load it on individual devices (“side loading” I think is the term). Is that correct?

Well, connecting my iPad to my PC with a USB cable only allowed me to see the DCIM folder on the iPad which is just the photos and videos. The rest of the file system and any app-specific files - like those for the Kindle app - are not visible.

But, the AnyTrans app I mentioned does work! It allowed me to transfer an epub file to the “Books” folder, but didn’t allow a mobi file to be transferred. Sadly though, transferring the epub version of the mobi book I wanted to get to Kindle went to the Apple Books app library instead. In addition, the epub file is below the 50 MB “Send To Kindle” app limit, but epub is not a file format it allows to be sent that way! What a PITA.

So, at this point, I am back to square one. This really shouldn’t have to be this dang hard.

I don’t suppose you are a user of Calibre? It can convert a large number of formats and can make wireless both wired and wireless connections with readers. There is also a plugin available for removing DRM.


I don’t suppose you are a user of Calibre? It can convert a large number of formats and can make wireless both wired and wireless connections with readers. There is also a plugin available for removing DRM.

Thanks. I briefly looked at Calibre a while back, and though it seems to be very well supported and highly capable, it also seems to be pretty complicated. Maybe I’ll have to give it another go.

Now, it turns out that although the mobi file that I downloaded on the iPad from the vendor (delphiclassics.com) ss 52.3 MB in size, which exceeds the 50 MB “Send To Kindle” limit, the mobi file I downloaded on the PC from the vendor is only 49.8 MB which is just under the 50 MB limit! The result is that I can use “Send to Kindle” from my PC for this book, but not from my iPad! Why the size is different I’m not sure. Perhaps the iPad uses a larger block size or some such thing. The actual number of bytes in the file should be the same, though I am so far not able to see that info on the iPad. On the PC, the file is exactly 52,295,271 bytes in size, and only 2500 bytes larger “on disk”.

So, in this particular case I lucked out, but the general problem of the 50 MB limit remains. For now at least.

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Try this with a large .mobi file (if anyone’s having similar problems with a .epub file, this should work there too with the obvious tweak):

  1. make a copy, changing the extension from “.mobi” to “.zip”
  2. decompress the file into a folder
  3. look in the folder to see what’s so big. Maybe some large pictures? (jpeg pictures don’t compress worth a darn - because they’re already compressed.) Find something, or some collection of things, that is big and you’d be content to not have in the book
  4. make another copy of the .mobi file, leaving the extension alone
  5. using a .mobi editor (Calibre is the most well known one but I doubt if it’s the only one) open up the copy from #4 and delete the thing(s) you found in #3. Save the result and see how much it’s shrunk.

1) make a copy, changing the extension from “.mobi” to “.zip”
2) decompress the file into a folder

Good idea, but it didn’t work for me. The result was a zip file that couldn’t be recognized as a zip file. Some brief googling seems to imply that other software is needed to unpack a mobi file, at least on Windows which is where I tried it.