Resend request in network tab is immediately blocked

I am having an issue when I want to resend a request through the network tab. It happens on my site, where nothing changed for one year.

The first request made by the app is OK, but when I am trying to resend without modification I am receiving blocked status with information in the console:

he resource at “xxxxxxxx” was blocked by OpaqueResponseBlocking. Reason: “Javascript validation failed”.

The request is hitting the backend because I can see logs of the backend, but the problem is that I am not able to see the response “No response data available for this request”, status of Request is Blocked, but in details I can see “OK”

How to resolve the issue, how to turn off validation?

Hi, this seems related to opaque response blocking, which is under the preference browser.opaqueResponseBlocking.javascriptValidator. You could turn this off in about:config.

At the moment this preference is turned on in Nightly channels and “early beta”. Developer Edition is almost identical to beta in terms of releasing. And early beta means this preference will be true in the first few versions of a beta cycle (for instance to gather feedback), and then turned off for the “late beta cycle”. This was a recent change ( so it’s probably the first beta version impacted by this.

The feature itself is being specified at:

Is there any way you could share a public link where we can reproduce the issue? If you get into this problem without modifying anything in the request, then it’s probably a DevTools bug and we should investigate.

(edit: I filed to track this on our side)


thank you! It worked when I disabled browser.opaqueResponseBlocking.javascriptValidator.

I can not share the link fully public (directly in this post), the problem is that these projects are mostly internal. Also, I was trying to compare working and not working requests and the difference was only in the initiator,

if it’s fine for you, can you send us the link in a DM on (either me, nchevobbe or julian, jdescottes) ?

thanks a lot!

@ Nicolas_Chevobbe

I have the same since two weeks or so. I can’t see send images in the chat @ - the src will always return 404.
It’s only Firefox related!

Set browser.opaqueResponseBlocking.javascriptValidator to false works.

FF v120.0 and now v120.0.1 :wink:

I have the same issue since a few weeks for a page that worked correcly before.
I have look the parameters but I can’t find where I can change opaqueResponseBlocking
Thanks for help.

Described fix worked for me aswell. The issue was observed with whatsapp web only for me (; Dev Options Console output: “a resource is blocked by opaqueresponseblocking whatsapp”)

This happened when a link, video or image was pasted into whatsapp web chat to share. The tab “crashed” and was unusable, sometimes not closable for a few seconds.