How can I disable "add application for mailto links" bar in Firefox?

Question

Every time I log on to my webmail I see a bar like on image below. I don't want to add this as an application and it is pretty annoying to close this every time. How can I disable it permanently?

The bar says this:

EDIT:
I tried to use Firebug to see what causes this bar to appear but with no luck. Anyone help?

EDIT 2:

Su's answer from http://webmasters.stackexchange.com :

This is done by registering a protocol handler. From that page:

navigator.registerProtocolHandler("mailto", "https://www.example.com/?uri=%s", "Example Mail");

The site would just have to run a similar snippet at an appropriate moment(login, in your case).

Link: registering a protocol handler

How can this be blocked?

Answer 1

have you tried going to about:config

There are some keys in there relating to mailto:

network.protocol-handler.external.mailto;true
network.protocol-handler.expose.mailto;false
network.protocol-handler.warn-external.mailto;false

You could try toggling them, I can't test as I can't recreate whats happening for you, I think maybe the first of the three to false maybe a good start,

Be careful when editing this config as it may cause strange things to happen maybe even break firefox.

Answer 2

It insists on being added, right? So try the following.

• Add it.
• Go to Firefox Settings / General / Applications.
• You will see that next to mailto there is a combo box of options to handle mailto links. That which you just added is in the list of options. Most probably it is the selected option.
• Just choose another one; the one which was selected before the first step.

As a result

• the message will never appear again (since you clicked Add application in the first step),
• Firefox will operate as before (since in the last step you chose the mailto app, which was in use before the first step).

Definitely the message should contain a "Don't ask me again" option, which is a bug in Firefox, as Danny Garside pointed out.

Answer 3

This looks like it has been a persistent bug in Firefox for ~10 years.

There's also a more recently raised bug with a broader scope that might encompass this one.

The only solution I have found ([1],[2]) has the unfortunate side-effect of disabling the operation of all mailto links.

1. open new tab page address: about:config
2. find variable: network.protocol-handler.external.mailto
3. double-click it to set to false

Answer 4

Another little bad news, because Mozilla has made another change that's why now it didn't work with Firefox-v70.

As you can probably guess, apparently the file "userContent.css" can't rectify this trouble anymore... And no I wasn't able to find another solution even with the file "userChrome.css" But at least, it could be reactivate :

lockPref("toolkit.legacyUserProfileCustomizations.stylesheets",true);
## How to remove the button close on every tabs ?
## Just recopy this example inside the "userChrome.css"
@-moz-document url(chrome://browser/content/browser.xhtml)
{
    .tab-close-button {display:none !important;}
}

So thank you @0x7c0 because I had found this solution :

lockPref("network.protocol-handler.external.mailto",false);
## At this moment, the notification has vanished on the new website of Tutanota.
## Which can be reach only at this new adress : "https://mail.tutanota.com/login"
## That's right, now the previous adress : "https://app.tutanota.com/#login" doesn't seem to exist (at all).
## I will assume Tutanota has probably made the choice to remove it.

PS : For the record and for once reddit was hepful.

Answer 5

… disable it permanently?

Mozilla bug 668577 - registerProtocolHandler notification should provide a "don't ask me again" button draws attention to How to hide/disable Firefox notification for addon/application | Firefox Support Forum | Mozilla Support (2011-06-30))

https://github.com/MrAlex94/Waterfox/issues/680#issuecomment-401004043 gives a (legacy) Stylish 2.1.1 workaround that's effective for:

Add Tutanota

Add o2 Poczta

For this case, you could try:

@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);

/*
Adapted from https://support.mozilla.org/questions/994658#answer-556629 
for https://superuser.com/q/363827/84988
*/

notification[label^="Add o2 Poczta"][value="Protocol Registration: mailto"] {
  display: none !important; 
}

Firefox Quantum might require a different approach but the essence of the workaround should be the same; styling.

Answer 6

There seems to be a new about:config option in Firefox (at least in 125 there is, but probably added earlier) - browser.mailto.dualPrompt, which, when set to true changes the message and the button to two buttons - "Set Default" and "Not now". Clicking "Not now" seems to add the handler to the list, but doesn't make it default and thus stops asking (survives browser restart, dunno if it will show later).