External media

If a large number of images makes your project too big, you can store your images in a separate repo and serve them on a separate server for PDF and web output.

There is a template repo for external media at

Setting external-media paths

You set the full URL for the remote-media location in _data/settings.yml. The remote-media paths must be full URLS. For example:

  live: ""
  development: ""

To disable external media, just comment out the relevant settings or leave the values blank:

  live: ""
  development: ""

Structuring external-media files

At the remote-media domain, the paths to media should match the paths to that media in this project.

For example, if a project called superpotatoes contains two books, mondial and fabula, the remote-media URL might be And on that media server, web images would be stored in and

Images inserted by CSS (e.g. background-image files) cannot be in external media, because their paths are fixed in CSS. So do not move these to the external media location.

Epub and app output

External media does not work for app or epub output. For apps with enough images to warrant external media, it’s recommended that you use a separate Cordova-based repo for your app, into the www folder of which which you simply copy-paste your app-ready HTML.


When using remote-media, translations must have their own image files in their translation subdirectories (e.g. That is, unlike local images they cannot inherit their parent language’s images in the absence of their own images folder.

Local media

Remote media works well for web output, but it means you have to be online, and can make PDF output very slow, because Prince has to fetch every image over the Internet. For faster PDF output you can tell the system to use images on your local machine instead by setting a local-media path, in addition to remote-media.

When a local-media path is set, PDF outputs will use that path to images, so that Prince does not have to fetch every image over the Internet.

The local-media path can be set in two ways:

  1. As a path on your computer’s filesystem, relative to the _site folder.
  2. As a URL served locally, by a webserver running on your machine.

Setting a filesystem path

A relative filesystem path might look like this:

  live: "../../superpotatoes-media"
  development: "../../superpotatoes-media"

(Currently, the live local-media path is not used; but this might change in future. For example, the Electric Book Manager may use the live setting in future. So we recommend setting both for now.)

Note: The development build is the default build type. A live build only really applies to web builds. We set build: live in, which is generally only used for building live website packages.

We recommend that you store your local copy of the external-media directory alongside the main project repo directory, to make the filesystem path to the local images simple.

To use external media from a directory alongside the main project repo, then, you would write the path to go up two levels (../../) and into the external media directory, as shown above.

Setting a local URL

Web output cannot use a relative filesystem path, because a webserver cannot see outside of its own root directory on your filesystem.

So you can use a webserver running on your own machine for offline development, e.g.

  development: "http://localhost:5000"

If you use the electric-book-media template for your external media repo, the OS-specific run- scripts there will launch a local server running at that address. You can run it at the same time as your local Jekyll instance of your book project.