Fenced diagram block renders as plain code instead of a picture
What you are seeing
A fenced diagram block renders as plain code instead of a picture.
#Why it happens
Either the language is not one of the 27 supported diagram languages, or no signed-in session token was available, in which case the block is left as-is with no error.
#What to do
Check the language name against the supported list, and reload the page so the session token is issued. Diagrams do not render for logged-out viewers.
#Settings involved
Setting | Where | What it does |
|---|---|---|
Administration settings | Nowhere | - |
#Limits that apply here
Limit | Value | What happens |
|---|---|---|
Diagram languages | 27 languages | Only blockdiag, bpmn, bytefield, seqdiag, actdiag, nwdiag, packetdiag, rackdiag, c4plantuml, d2, dbml, ditaa, erd, excalidraw, graphviz, mermaid, nomnoml, pikchr, plantuml, structurizr, svgbob, umlet, |
Session token lifetime | 20 minutes | The short-lived token that authorises diagram rendering and image proxying lasts 20 minutes and is refreshed after 18 minutes, on window focus and on reconnect. |
#A few things that catch people out
There is no admin or project-level configuration at all: no access restrictions, no diagram-language toggles, no self-hosted renderer setting, no approved-domain management.
Permission enforcement is app-managed, so newly requested permissions ship to all installs immediately and sit pending admin approval rather than blocking the install.
#Related
Found it? Good.
