I must open jnlp-files directly with firefox

[PfeifferAachen]

Although the settings specify that jnlp should be opened with Java WebLauncher, this is not done for security reasons. It must be possible to store an exception /whitelist in Firefox.

[Jon]

Thanks for submitting an idea to the Mozilla Connect community! Your idea is now open to votes (aka kudos) and comments.

[jscher2000]

Currently, there is a global preference, not restricted by content type, file extension, or website. So that is not ideal, but if you open .jnlp files frequently, you might want to use it. Here's how you set it up:

(A) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

More info on about:config: Configuration Editor for Firefox. Please keep in mind that changes made through this back door aren't fully supported and aren't guaranteed to continue working in the future.

(B) In the search box in the page, type or paste browser.download.skipConfirmLaunchExecutable and pause while the list is filtered

Firefox should display a bar with Boolean Number String and a plus button. If instead Firefox display a row with true or false and a trash can at the far end, skip to (D).

(C) Keep the Boolean data type and click the + button to add the preference

(D) If the value is false, double-click the preference to switch the value to true

[jscher2000]

By the way, there is some strange glitch with the "default" program Firefox selects for JNLP. As shown in the attached screenshot, you get better results if you click Use other... and go find the proper launcher (for me, that was "C:\Program Files\Java\jre1.8.0_321\bin\javaws.exe").

[godlo]

FF 109 64bit
I tried the "browser.download.skipConfirmLaunchExecutable" solution without any luck. 😞
It still only download JNPL instead asking.
Plus In "Applications" there's no "JNPL file" to configure. 😞

SOLVED:
I solved installing Firefox ESR

[alex-valenzuela]

You can add JNLP to file associations on latest firefox, no need to use ESR
add this on the right place to "handlers.json" on your Firefox profile directory...

"application/x-java-jnlp-file": {
"action": 4,
"extensions": [
"jnlp"
]
},

https://support.mozilla.org/en-US/questions/1262664

[ELCARS]

Tape in class:

"browser.download.viewableInternally.enabledTypes = xml,svg,webp,avif,jxl,jnlp"

and goes to!