During an extension development, I noticed that the Firefox debugger console doesn’t display any errors while injecting content scripts, for example, a syntax error, which I reckon would be quite common during development. To test this, I injected pure garbage as a script, and console had no indicat…

Just stumbled on this bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1410932 . The error was indeed displayed on the Browser Console!

I assume you’re looking in the Web Developer Tools console of the page the script is injected in? https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Debugging#Debugging_content_scripts

Yes, I’m. That’s where I’d expect all content script output anyway!

Iirc load errors of the script (which includes syntax errors) are logged to the browser console/add-on debugger since the script is never actually injected. I’m sure others will correct me if I’m wrong on that.

I think the Firefox console only reports uncaught errors. Syntax errors in content scripts injected with tabs.executeScript() are reported to the background page, and are thus not uncaught. (Which is similar to what Martin Giger said.)

I’m talking about a content script mentioned in the manifest, and not injected from a background page. For example, "content_scripts" : [{ "matches": [ "<all_urls>", "file:///*/*" ], "js": [ "test.js" ], "run_at": "document_end" }] with test.js containing: console.log("befor…

@jeenuv , could you be more specific as to what you mean by “the browser console”? I have the same problem now and can’t find the error outputs anywhere. Thanks!

There is multiple console windows - sometimes some webextension errors are not logged into Web Console (the one you see when you press F12 or Ctrl + Shift + K), but only in Browser Console (Ctrl + Shift + J). You can find it also through the Firefox main menu / Web Developer. Related bugreport for …

Small mistake, the shortcut for the browser console is Ctrl + Shift + J.

Console doesn't display content script errors

Add-ons Development

jeenuv (Jeenu) December 4, 2017, 7:28pm 5

Well, the script is injected. I could see all console.log messages before a syntax error, for example.

Topic		Replies	Views
Why don't I see my extension's content scripts in the Debugger pane Add-on Support	5	952	September 1, 2024
Why I can't see the content script when I debug the addon? Development	12	8732	April 11, 2026
Console logging Development	9	8471	October 11, 2019
Temporary add-on's content script isn't showing up in tabs Development	0	391	July 8, 2021
WebExtension - Debugging background-script and browser-action? Development	8	16016	April 7, 2016

Console doesn't display content script errors

Related topics