You can configure a number of settings for the draw.io backend in Confluence Server. These settings are entered as a list of key=value pairs.


  1. As an administrator, click on the gear icon, then select General configuration.
  2. Under the draw.io add-on section in the left panel, click on Configuration.
  3. Click on the Configuration tab.
  4. Paste your configuration in the Server Configuration field, then click Save changes.

Supported key=value settings

  • htmlscale: Specify the scale used for rendering HTML labels on the server-side. This setting is used when creating and exporting images in Safari and IE11 (and earlier versions), if useExternalImageService is not enabled. The default is 0.6 in version 6.5.6, and 0.63 in later versions on Linux, and 0.75 on all other operating systems. This defines the ratio between pixels when HTML is rendered as well as the units used for rendering other graphics elements.
  • serveroffline: Set a flag to enable or disable the use of any external services from the Confluence server(s). These are extended icon search and cross-domain proxy load. 

The extended icon search uses external draw.io servers to find additional matches for shape search queries search service for icons after the built-in search runs out of matching icons. Queries are anonymised at the draw.io servers and deleted after the request is made. Enabling serveroffline disables extended searches.


If external images are embedded into the diagrams, that are hosted cross-domain from the domain of the Confluence server, the browser cannot generate an image output of the diagram due to CORS errors. In order for cross-domain images to be displayed in diagram image representations, they must be loaded via a proxy server. The server is external to avoid SSRF issues with the Confluence Server loading the images. Enabling serveroffline disables proxying.


The default is 0 (external calls enabled).


  • vsdurl: Link to our external server to be able to convert .vsd and .vss files. You cannot convert these files on the Confluence Server instance itself. Note the entire diagram file is sent to our servers, which have our usual strict security policies applied. Set vsdurl=https://convert.draw.io/VsdConverter/api/converter.
  • customlibs: Toggle the custom libraries feature on or off. The default is 1 (enabled).
  • viewerurl: Set the location of the JavaScript file needed to display diagrams exported to HTML. You can host this file within the intranet. The default is https://www.diagrams.net/js/viewer.min.js.
  • emf2png: Use our external server to convert .vsd and .vsdx diagrams that contain EMF images to prevent some converted shapes displaying as black rectangles with crosses. You cannot convert EMF images on the Confluence Server instance. Set emf2png=https://convert.draw.io/emf2png/convertEMF to enable this functionality. Only the EMF image is sent to our servers, which have our usual strict security policies applied
  • emailpreview: Toggle whether diagram previews in emails and rest API calls are enabled or disabled. Default is 1 (enabled).
  • macrooutputtype: Sets viewer container layout. Available values are block and inline. Default is block. (since 9.4.1)


For example, several of these settings have been added to the Server Configuration field.