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Generation Preferences

In Generation Preferences, you can control aspects of the files created during Book Generation.

Accessing Generation Preferences

You can access Generation preferences by going to the Vellum menu and selecting Preferences:

The Preferences command shown in the Vellum menu

Note: On macOS Ventura, this will be labeled as Settings

Select the Generation tab to find the available controls:

The Generation Pane in the Preferences dialog


For Kindle, you have control over how Vellum resizes images for ebooks and the types of ebook files Vellum generates.

Kindle Image Sizing

Vellum resizes and reformats images for every ebook platform. For Kindle, you can decide whether you prefer images with Higher Quality or Smaller Size:

Higher Quality
Vellum resizes images so that a full-width image is no more than 1200 pixels wide. Images are optimized with high-resolution devices in mind, with a small amount of compression to decrease file size.
Smaller Size
Vellum resizes images so that a full-width image is no more than 800 pixels wide. More aggressive compression is used to help further reduce file size and delivery costs.

Kindle Ebook Formats

Vellum can generate Kindle ebooks in both epub and mobi formats. When generating, you can choose between:

  • EPUB Only

By default, Vellum generates EPUB Only. When you’re ready to publish your ebook, Amazon requires uploading a file in this format. Before you upload, you can proof your Kindle epub using Kindle Previewer.

If you want to sideload your ebook onto a Kindle — for your own testing or to send to an advance reader — you may need a file in the mobi format. You can generate this additional file using the EPUB + MOBI option.

The following summarizes how you can use Kindle epub and mobi files:

Proof with Kindle Previewer -
Upload to KDP -
Send to Kindle (App) ✓*
Send to Kindle (Email) ✓*
Sideload via USB -
* MOBI support is ending in late 2022 soon

Generic Ebook Format

For Generic output, you can control whether Vellum generates an EPUB 2 or EPUB 3 file:

Vellum defaults to this older version of the EPUB format, as it offers better compatibility across platforms.
This newer version of the EPUB format includes more information for accessibility and can support features like Endnote popups. Some stores may not accept this format, however.