Guide
Why Isn't My Canvas Extension Loading? How to Fix It on Custom Canvas Domains
The most common reason a Canvas extension or userscript doesn't load is that your school runs Canvas on its own custom domain (like canvas.asu.edu or lms.yourschool.edu) instead of canvas.instructure.com, and the tool doesn't recognize the page as Canvas. The second most common reason is a browser permission that got switched off. Here's how to diagnose and fix both.
Key takeaways
The usual culprit is that your school runs Canvas on a custom domain the extension does not recognize.
Second most common: a browser update silently reset Developer mode or user script permissions.
Site access must be on all sites, or your school's domain must be allowed, for Canvas tools to activate.
CanvasTool detects Canvas itself rather than a fixed URL, which is why it works on institutional domains.
Why do custom Canvas domains break extensions?
Many extensions are configured to activate only on *.instructure.com addresses. Universities and school districts frequently host Canvas on their own subdomain, so when you visit canvas.yourschool.edu, the extension never activates because the URL doesn't match what it's watching for.
Well-built Canvas tools solve this by detecting Canvas itself rather than a fixed URL, since every real Canvas page exposes identifiable Canvas markers regardless of the domain. CanvasTool uses this approach, which is why it works on institutional domains out of the box.
Step-by-step fix checklist
Work through these in order:
1. Confirm you're on an actual Canvas page. Course pages, the dashboard, and grades pages count. Your school's general portal page (before you enter Canvas) doesn't.
2. Check the extension or userscript is enabled. For extensions: your browser's extensions page, confirm the toggle is on. For userscripts: open the Tampermonkey dashboard and check the script's enabled switch.
3. On Chrome and Edge, check Developer mode and user scripts. Userscript managers need Developer mode enabled at chrome://extensions/ (or edge://extensions/) and user scripts allowed in the manager's details. Browser updates occasionally reset these, which silently kills every userscript you have. This is the #1 fix for "it worked yesterday."
4. Check site access permissions. Click the puzzle-piece icon, find your extension or Tampermonkey, and make sure site access is set to "On all sites" or that your school's Canvas domain is allowed. If it's set to "On click," the tool only runs when manually triggered.
5. Hard refresh. Ctrl+Shift+R (Cmd+Shift+R on Mac) after any change.
6. Test in a clean profile or incognito. Enable the extension in incognito (extensions page, details, Allow in Incognito) and try there. If it loads, another extension or a cached session is interfering in your main profile.
What if it still doesn't load?
If you've cleared the checklist and the tool still isn't detecting your school's Canvas:
- Grab your exact Canvas URL (the full address bar while on your dashboard).
- Contact the tool's support with that URL. Domain detection can be verified against your school's setup quickly. For CanvasTool, the fastest route is the support page, which connects to our Discord.
Setup problems with CanvasTool specifically are usually one of the permission steps above; the install guide walks through the full setup with screenshots of where each toggle lives.