Kindle X-ray overview and guide

It’s time to another self-publishing guide, this time to Amazon’s Kindle X-ray feature. In this post, I’ll say what this tool does, what uses it has, and how to set it up.

What is it?

To tell it simply, Kindle X-ray is digital version of a book’s glossary – but buffed up a lot. Instead of having a glossary on the back of the book like it is with print, it’s built-in into the file and allows the reader to look up the terms (mostly characters and places – more on that soon) just by highlighting the word instead of going to the back of the book, looking it up, and going back.

In general, there are two major cases when Kindle X-ray is useful: scientific texts (where a lot of expert-level terms will be used) and fiction with a lot of characters or custom terms. This applies a lot to fantasy (custom creatures, spells, etc) and Sci-Fi (custom tech), but can work well for any genre.

Setting up Kindle X-ray takes a while (how long is determined by the size of your glossary) and the UI is quite intuitive. If you’ve been making a glossary while drafting, then you have much of the work done already and it’ll be just a matter of copy-pasting those descriptions…

Enabling X-ray

If you want to use this tool for your book, enabling X-ray is done from your KDP bookshelf.

Where to find it…

Before you enable it, the ‘Launch X-ray’ text in the screenshot above will be something like ‘Enable X-ray’ – clicking that will give you a pop-up saying this may take 15-30 minutes (you’ll get an e-mail when it’s done). What happens is that some algorithm goes through your book and makes a list of words that should be in the glossary. This includes all names (determined by capital letters) and some other terms (such as ‘shield wall’ in my case). You can, of course, add anything the auto-search missed and disable anything that it found but you don’t think it’s important enough for the glossary.

For any term, you have pretty much four options: excluded (won’t show), custom description (written by you), Wikipedia description (coming from Wikipedia, mostly relevant for real-world geography or any scientific terms), and excerpt. Now, excerpt doesn’t really show anywhere – it’s pretty much an automatic placeholder for when you enable a term but don’t add a custom description (and don’t choose Wikipedia or it’s a custom word).

An example of Wikipedia description for Shield wall

The sad part, from a reader’s point of view, is that I saw several books where the author enabled X-ray but left it at excerpts, which are… not useful at all in 90%+ of cases.

Creating the glossary

X-ray UI filters

To help you navigate potentially large amount of terms, the X-ray UI has a set of built-in filters. Amazon recommends using X-ray descriptions for terms that appear at least three times, but it’s up to you as the author to decide what is important or not. For example, I haven’t included descriptions for some characters that would be potential spoilers (though they’ll have a description in the sequels, when it’s not a spoiler anymore). You can also publish the X-ray definitions in batches but, apart from fixing issues, I don’t recommend this once the book is live. The issue is that the X-ray glossary won’t automatically refresh on the reader’s device so it’s better to have it all prepared beforehand. And even force-syncing my Kindle failed to update the X-ray glossary for me.

The X-ray description can be up to 1200 characters, but Amazon recommends one paragraph or less. Given the screen size of an e-reader, I’d say 1-2 sentences work the best – longer definitions would mean the reader has to scroll through them. After all, the purpose is a quick reminder what the word means, not a wikipedia-style article (the place for an encyclopedia of your fictional world is on your author website).

As the screenshot above shows, any term can be in five possible states: unpublished (this is pretty much the ‘excerpt’ state – enabled but no description), modified (changes made but not yet confirmed), pending publication (changes made and to be processed in the next batch – more on that soon), published (definition is live) and excluded (word won’t appear in the X-ray glossary).

X-ray UI, costum description

One of the major parts is the ability to merge terms. This is mostly for characters, not so much for other terms. As shown in the screenshot above, this allows you to connect various forms of a name – first name only, first and second name, including/excluding titles, etc. They don’t have to match, so you can even include nicknames.

From my experience (reading though the live version of my book), Kindle X-ray isn’t smart enough to process possessive forms ([name]’s) but whether this is worth adding manually for every single name… I’m not sure. Most of them will appear enough times in a ‘normal’ form anyway.

Also, as I said in the HTML formatting post, using HTML shortcodes for apostrophes instead of an apostrophe will cause X-ray to not ‘read’ the word properly (and thus only the part before the first apostrophe will be recognized).

Confirming the changes

Once you’re done for the current batch, click ‘Review and Publish X-ray’. You’ll get a confrimation screen and, until the changes are processed, will be locked from accessing the X-ray UI (and making further changes). As with enabling X-ray, this takes only a while.


I hope you may’ve found my look into this Kindle feature interesting. As always, feel free to ask questions, and I’ll do my best to answer. And if you’re a self-published author (or will be soon), feel free to share your thoughts and/or experiences. Are you planning to use a glossary for your book? And if yes, would you consider using X-ray over the traditional ‘passive’ approach for the Kindle version of your book?

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