To configure the backend in the Add-on Configuration tab of CONFLUENCE_BASE_URL/admin/drawioConfig.action, a list of key=value entries can be added. Currently, the following keys are supported:

  • htmlscale: Specifies the scale used for rendering HTML labels on the server-side. This setting is used for creating and exporting images in Safari and IE11 and earlier, if useExternalImageService is not enabled. The default value for this setting is 0.6 (in version 6.5.6) or 0.63 (in later versions) on Linux and 0.75 on all other operating systems. It defines the ratio between px units for rendering HTML and the units used for rendering other graphics elements.
  • externaliconsearch: A flag that controls whether or not to enable the use of external image search service when searching for icons in editor. Default settings enables external icon search. Using externaliconsearch=0 disables it.
  • vsdurl: for Confluence server cannot convert .vsd or .vss files on the Confluence Server itself. It's possible to link our external server to enable conversion of these file types. Note the entire file is sent to our servers, which have our usual strict security policies applied. The value of this entry is the URL of the .vsd converter, which is
  • customlibs: A switch that toggles the custom libraries feature. Set it to 0 to disable custom libraries, otherwise they are enabled.
  • plantuml: Enables the SVG generation using Plant UML syntax. The PlantUML server is not built into You can either use the service we provide at or host PlantUML server yourself and reference that. Our custom version of PlantUML and server are built at Take the latest release and use a servlet engine, like Tomcat, to host the war.
  • viewerurl: HTML exported diagrams require a JavaScript file to display. This is the URL of the viewer JavaScript file which can be hosted within the intranet. If left blank, it defaults to
  • emf2png: Some .vsd and .vsdx diagrams contain EMF images. We cannot convert EMF images on Confluence Server, this requires our external server service. If you find these files convert some shapes to black rectangles with crosses, it's likely they contain EMF images. Assign to this key to enable this functionality. Only the EMF image is sent to our servers in this case and the standard security precautions are applied.
  • emailpreview: A switch to enable or disable diagram previews in emails and rest API calls.  Set it to 0 to disable it. Default is 1.

In the Server Configuration it will look like this: