Fixing "Your Web Part Will Not Appear in the Toolbox" Issue in SPFx Workbench

 If you're working with SharePoint Framework (SPFx) and encounter the frustrating error "Your web part will not appear in the toolbox" after running gulp serve, don't worry—there’s a simple fix!

Many developers face this issue where the workbench fails to load the web part even after restarting gulp serve multiple times. When checking the browser console, you may see an error like this:

nginx
Failed to load debug manifests: Error: Script error for: https://localhost:4321/temp/manifests.js

This error indicates that the debug manifest files required to load the web part are not loading correctly.

Quick Fix for the Issue

Follow these simple steps to resolve the problem:

1. Open a New Browser Tab

   • Copy and paste the following URL into the address bar:

     bash
     https://localhost:4321/temp/manifests.js
     

   • Press Enter to load the URL manually.

2. Bypass the Browser Warning

   • Your browser might display a security warning or an error message.
   • Force the page to load (for example, in Chrome, click Advanced > Proceed to localhost (unsafe)).
   • If successful, you should see a JSON response in the browser.

3. Refresh the Workbench

   • Go back to your SPFx workbench (https://localhost:4321/workbench) and refresh the page.
   • Your web part should now appear in the toolbox! 🎉

Why Does This Happen?

This issue occurs because the browser sometimes blocks localhost requests due to security restrictions. Manually loading the manifest file helps the browser trust the request and allows your web part to load properly.

Conclusion

Next time you face the "Your web part will not appear in the toolbox" issue in SPFx, try manually loading the manifest file before restarting gulp serve. This quick trick saves time and gets you back to development without unnecessary debugging.