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Last Reviewed: July 27, 2020

External Libraries on Pantheon

Learn to incorporate external libraries on the Pantheon Website Management Platform.

There are some scenarios when an external library is required. The Pantheon platform includes a number of PHP extensions and common libraries that are available for use.


wkhtmltopdf allows you to create a snapshot or capture the content of a web page easily in a PDF. Wkhtmltopdf version 0.12.5 (with patched qt) is currently installed on the Pantheon Platform. For more information regarding the qt patch, read the wkhtmltopdf documentation.

wkhtmltopdf is located in your application container at /srv/bin/wkhtmltopdf. You must install or create a compatible plugin or module to complete the following steps:

Download and enable the Print module from the Drupal Dashboard, or using Drush via Terminus:

terminus drush <site>.<env> -- en print --y

Create a symlink to the hosted library and your site's libraries directory via Git:

mkdir -p sites/all/libraries/wkhtmltopdf
ln -s /srv/bin/wkhtmltopdf sites/all/libraries/wkhtmltopdf/wkhtmltopdf
git add .
git commit -m "Added wkhtmltopdf library"
git push

Unable to Generate PDF File

Due to a known issue in wkhtmltopdf 0.12.5 and sites that use the CSS quotes property, some users may have issues with downloading a PDF created by wkhtmltopdf. In Live environments, creating a PDF fails silently. On Dev, you'll encounter the error Unable to generate PDF file.

To confirm the source of the error, log in to the Drupal Admin and click Reports in the menu, then Recent Log Messages and look for print_pdf or (returned 127): No stderr output available.

If you encounter this error, remove the offending quotes property from the CSS.

PhantomJS (Unsupported)

In its own words, PhantomJS is a headless WebKit with JavaScript API. It has fast and native support for various web standards: DOM handling, CSS selector, JSON, Canvas, and SVG.

However, PhantomJS development has been suspended until further notice. While Pantheon continues to include the following binaries, they may be removed in the future.

  • PhantomJS (1.7.0) is located at /srv/bin/phantomjs on your application container.
  • PhantomJS (2.1.1) is located at /srv/bin/phantomjs-2.1.1 on your application container.

Recently, PhantomJS started erroring on domains with Let's Encrypt. A known workaround for this is to ignore SSL certificate errors using the following option: --ignore-ssl-errors=yes

Drupal PhantomJS Configuration

After you've downloaded and enabled the PhantomJS Capture module, you'll need to configure the image toolkit settings. Go to the image toolkit settings page at /admin/config/user-interface/phantomjs_capture to specify the library path.

Apache Tika

The Apache Tika toolkit detects and extracts metadata and structured text content from various documents using existing parser libraries.

Tika can extract content from a number of document formats such as HTML, XML, Microsoft Office document formats, and PDFs and more.

See the Solr for Drupal guide for instructions on using Apache Tika with Pantheon Drupal sites.

There are no known plugins in the repository that will enable the use of Tika.

Older Versions

Pantheon also supplies the following older version of Tika:

  • /srv/bin/tika-app-1.1.jar

Sites that are using an old version of Tika should be upgraded to the supported path as soon as possible.


ImageMagick is a software suite to create, edit, compose, or convert bitmap images. It can read and write images in a variety of  formats (over 100) including  DPXEXR, GIF, JPEG, JPEG-2000, PDF, PNG, Postscript, SVG, and TIFF. Use ImageMagick to resize, flip, mirror, rotate, distort, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and Bézier curves.

To check the available version of ImageMagick on Pantheon, refer to the PHP 8.3 Info page here.

Drupal ImageMagick Configuration

Once you have downloaded and enabled the ImageMagick module, you'll need to configure the image toolkit settings. Go to the image toolkit settings page at: admin/config/media/image-toolkit to select ImageMagick.

When creating a new preset, if the "Division by Zero" warning appears, add the image_allow_insecure_derivatives conf variable to your settings.php file.

Some modules (like ImageAPI Optimize) require the explicit path to the ImageMagick library. Use the path /usr/bin/convert.

ImageAPI Optimize's support for 3rd-party services (like advpng and OptiPNG) are not available at this time.

WordPress ImageMagick Configuration

After you've installed the ImageMagick Engine Plugin, you'll need to enable it in your plugin settings and configure the settings. In the Regenerate Images sidebar, select the sizes you would like to reimage and click Regenerate.

ImageMagick Engine Settings

Regenerate button in sidebar

Troubleshooting and FAQs

How do I request the addition of a new library or a newer version of an existing library?

Please contact support with a description of your use case and a link to the library's webpage. We welcome new requests, but please bear in mind they are not guaranteed and it is possible the feature request may be denied. As a result, we recommend you set aside enough time for alternative solutions.

Will you set up and configure the module/plugin for me?

No. This is not within our scope of support. It is important to be aware of how a Drupal module or WordPress plugin is setup and how it functions. This will prove invaluable in cases where you need to plan and build your site.