Last updated: March 21, 2022

For security, compatibility and performance reasons, Pressbooks restricts the range of third-party plugins that are included on our hosted networks. Anyone interested in using a particular WordPress plugin with our hosted offering of Pressbooks is welcome to submit a plugin request. All requested plugins undergo a review process and are evaluated with reference to our plugins policy.

Please see below for a list of plugins evaluated to date and the results of the evaluation.

Permitted Plugins

The following third-party plugins have been tested and approved for use on Pressbooks networks.

Note: Available plugins may differ based on service level. Some plugins listed below are part of the Pressbooks hosting stack and may not be administered by network managers.

• Enable Media Replace. This plugin allows authors to replace media files uploaded to a book a single time in the media library rather than replacing it everywhere it has been inserted into the text.
• H5P. This plugin allows users to create, share and reuse interactive HTML5 content and applications, such as quizzes and assessments
• Hypothesis. This plugin allows authors to enable the Hypothesis web annotation client so that readers can highlight, comment, and interact with a text through social annotation.
• Koko Analytics. This plugin provides authors with privacy-friendly page visit analytics for their books.
• Lord of the Files. This plugin helps sanitize file uploads and can be used to allow users to safely upload SVG files.
• Parsedown Party. This plugin allows authors to write and publish content using markdown.
• Redirection. This plugin allows network managers to set up redirection rules for various URLs on your site.
• Regenerate Thumbnails. This plugin allows authors to regenerate the thumbnail sizes for uploaded images.
• TablePress. This plugin allows users to create, import, and display sortable, filterable tables.
• WP QuickLaTeX. This plugin lets users create equations and use other basic commands in LaTeX.

Disallowed Plugins

The list of disallowed plugins below is not a judgement on the quality or suitability of these plugins for various use cases. Plugins are generally disallowed because they are incompatible with the Pressbooks application in a non-trivial way, they duplicate functionality that exists within the Pressbooks application, or they do not meet the performance requirements of our enterprise hosting service.

• Broken Link Checker
  This plugin placed an unacceptable load on server resources when evaluated in 2017. Users who wish to check their networks/books for broken links may be interested in using the W3C’s link validator: https://validator.w3.org/checklink instead.
• CM Tooltip Glossary
  As of Pressbooks 5.6.0, Pressbooks now includes a native glossary tool which includes most of the functionality provided by this plugin. See https://guide.pressbooks.com/chapter/create-and-display-glossary-terms/.
• OpenStax Import for Pressbooks
  This plugin was closed in May 2019 and is no longer being maintained. Prior to the plugin being abandoned by its creators, the plugin required users to upload .zip files of the books in question, many of which are very large. The size of these files and the strain this process puts on server processes meant that we were unwilling to install the plugin on our production networks.
• Show/Hide Content
  As of McLuhan 2.3.0, Pressbooks now includes a web theme option to allow users to collapse and expand sections delineated by top-level headings within the webbook. See https://guide.pressbooks.com/chapter/appearance/#webOptions.
• Simple Custom CSS
  As of Pressbooks 4.3.0, users can enter custom CSS for web, ebook, or print stylesheets using the ‘Custom Styles’ tool. See https://guide.pressbooks.com/chapter/customizing-your-exports-with-custom-styles/.
• Simple Lightbox
  As of McLuhan 2.4.0, Pressbooks includes a lightbox feature for linked images that can be activated in web theme options. See https://guide.pressbooks.com/chapter/appearance/#webOptions.
• SSL Insecure Content Fixer
  On our hosted networks, our Nginx configuration serves all our network content over HTTPS, so this plugin would only be needed for third-party content.

Pressbooks maintains all Pressbooks-developed plugins to ensure they are functional and compatible with core Pressbooks functionality. Pressbooks will make reasonable efforts to ensure its core functionalities are compatible with endorsed plugins.

Request a Plugin Review

Network managers for Pressbooks networks may request that Pressbooks evaluate a third-party plugin for installation on their Pressbooks network. To request evaluation of a third-party plugin, please use this Google form.

Upon receiving a new form submission, the Pressbooks development team will test and evaluate the plugin for suitability for inclusion on our hosted networks. At the end of this evaluation, Pressbooks will inform the requester whether the plugin has been placed in the disallowed or endorsed category. In some cases, Pressbooks will inform the client that the plugin could be endorsed with additional custom development work, and may provide suggestions or an estimate for funding the requested development.

Before permitting a plugin to be installed on our hosted networks, Pressbooks reviews the plugin for suitability. We generally expect plugins to:

• be open source
• be actively maintained
• be compatible with WordPress multisite
• meet WordPress plugin standards
• meet our internal standards for performance, security, and privacy
• work well from a user perspective (does what it’s supposed to do)
• work on all supported output/export formats
• be broadly useful for many types of users or help users to accomplish common publishing tasks
• refrain from displaying unwanted notifications or advertising

Request Custom Development

If there’s a specific feature that you would like to be made available for your network or your users, we occasionally take on custom development projects for Pressbooks clients at additional cost. Custom development projects are selected based on how well they fit with our overall product goals, as well as our internal time and expertise constraints.

If you’d like to discuss a custom development project or idea, please contact sales@pressbooks.com. We will happily set up a call to discuss your needs and provide a quote.

We also welcome ideas and suggestions for new product features from users who are unable to fund their development. Our product owner regularly reviews suggestions made in our GitHub “Ideas” repository and adds them to our prioritized product backlog.