Monaco Editor and Glitch Project Environment: DOM Node Retention

Short answer

In Glitch’s web‑IDE, closing a file tab does not automatically call editor.dispose() on the underlying Monaco instance. The platform relies on the browser’s garbage collector to clean up detached DOM nodes, which can delay or miss cleanup, especially after many open/close cycles. As a result, long‑running sessions can accumulate ~2–5 MB per editor instance in memory.

What the platform actually does

• Glitch creates a new Monaco editor for each open file tab.
• The tab‑close handler removes the tab’s UI element but does not invoke dispose() on the editor.
• Detached DOM trees and event listeners remain until the browser’s GC runs, which may be non‑deterministic.
• No public API exposes a hook for the platform to perform cleanup automatically.

How to verify the leak in your session

1. Open Chrome DevTools (or Firefox) and go to the Console tab.

   monaco.editor.getEditors().length
   

   After closing all file tabs, the number should be 0 if all editors were disposed. A non‑zero value indicates undisposed instances.

2. Navigate to the Memory panel.
   • Take a heap snapshot before opening many tabs.
   • Open and close several tabs repeatedly.
   • Take another snapshot and filter for Detached DOM tree and monaco objects.

   Persistent detached nodes confirm that disposal is missing.

3. Optional: In the console, run

   monaco.editor.getEditors().forEach(e => e.dispose());
   

   and observe a drop in the heap size and the editor count.

What you can do now

• Use the manual disposal snippet above after closing a tab or at session end.
• If you are a Glitch maintainer, consider extending the tab‑close handler to call dispose() on the editor instance.
• Keep an eye on Glitch’s changelog; a future update may add automatic cleanup.

Missing diagnostic detail

To tailor a more precise recommendation, could you let us know which browser you are using and whether you have any custom extensions or Glitch plugins enabled that might register additional listeners? This information helps determine if the leak originates solely from Monaco or is amplified by third‑party code.