When I try to load an (unpacked) extension into Edge, why does it say that web_accessible_resources[0] is invalid?

Question

I'm building a browser extension for Microsoft Edge in which I need to inject a script into certain pages. Whenever I try to load the unpacked extension, Edge reports, “Error Invalid value for 'web_accessible_resources[0]'.” However, I've looked at the documentation and some examples and it appears that I have a valid configuration. Below is a minimum working example to reproduce the error:

---

manifest.json

{
    "manifest_version": 3,

    "name": "MWE",
    "version": "0.0.0",

    "web_accessible_resources": [{
        "resources": ["script.js"],
        "matches": ["<all_urls>"]
    }]
}

script.js

<empty>

---

I'm using Microsoft Edge Version 86.0.622.69 (Official build) (64-bit). Why am I getting this error? What can I do to resolve this? I'm able to use Manifest v2 with success, but I want to use Manifest v3.

Answer 1

I tried using the Manifest v2 format for web_accessible_resources. It loaded successfully, but it had a background error that said, “The maximum currently-supported manifest version is 2, but this is 3. Certain features may not work as expected.” I guess that solves that. Microsoft's documentation didn't make that clear.