Background colors

Images are generated with a transparent background by default.

As mermaid diagram with light themes are barely readable on dark backgrounds (and vice-versa), it is possible to force a background color by appending the following query parameter to any /svg or /img URL: ?bgColor=<color>. The color value is interpreted as an hexadecimal color code by default, but you can also use named colors by prefixing the value with !.


  • Add a red background using hexadecimal color: ?bgColor=FF0000
  • Add a white background using named color: ?bgColor=!white

mermaid chart example with background color