localhost:631 (cups) won't open on macOS Big Sur (11.2.3 (20D91))

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localhost:631 (cups) won't open on macOS Big Sur (11.2.3 (20D91))

This post is to answer to this previous post: https://discussions.apple.com/thread/252329817

My colleague found this worked and it seemed so crazy that I tried it and confirmed that it did!

I don't know why, but now we had the same fix for 2 mac's, so hopefully it will help others :-)

Before:

Then try this:

Open system preferences.

Go to Security & Privacy > Firewall.
Unlock your padlock with your system password.

Actually I think I unlocked mine at system preferences, then went to firewall?

Then... the technical part, get ready, it's pretty intense:

lock your padlock...

Now try localhost:631 again: both of ours worked...

I don't know why, but just thought it was easier than some other suggestions we have seen.

Hope it helps!

Luke.

Posted on Apr 7, 2021 12:37 AM

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Answer 1

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Luke__Skywalker Author

Level 1

4 points

Apr 7, 2021 9:03 AM in response to leroydouglas

Hi leroydouglas,

I think my original post (which is not editable) would have really benefited from the screenshots that I failed to add properly! Sorry for the confusion...

So, the issue is that localhost cannot be connected to.

I did write out the text from the error message in the second post (when I saw my screenshot was missing)... and then pasted the screenshot in my next one.

The issue is not that the interface is disabled.

You normally see this info on how to enable it if it is disabled, as you posted above. But again, that is not the issue.

I also wrote how odd it seemed that this workaround actually worked. But as it worked on 2 mac's that both could not connect to localhost:631 before and then could immediately after the steps detailed above I thought I would post it here hoping it would help others as the things in the other linked thread did not work, and were not as simple.

Hopefully this clears up the confusion.

To summarise it though:

First we had this when trying to get to localhost:631:

Then we did this:

Open system preferences.

Go to Security & Privacy > Firewall.
Unlock your padlock with your system password. (Actually I think I unlocked mine at system preferences, then went to firewall)
lock your padlock again...

Now try localhost:631 again: both of ours worked...

Again, I am no expert and I don't know why... but it did work. Twice. It's like snake oil... or Apple have a bug.

I only posted to be helpful. The previous thread was closed.

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Answer 2

Apr 7, 2021 6:32 AM in response to Luke__Skywalker

Luke__Skywalker wrote:

localhost:631 (cups) won't open on macOS Big Sur

I don't know why, but just thought it was easier than some other suggestions we have seen.

?

From the browser CUPS management, copy and paste:

localhost:631/admin

If no interface—

From the Terminal.app copy and paste:

cupsctl WebInterface=yes

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Answer 3

Apr 7, 2021 8:12 AM in response to leroydouglas

Thanks Barney-15E - yep, I just pasted them in! Doh... I know now, thanks :-)

leroydouglas, I know how to enable the interface, that was not the issue.

This screenshot below would have been the 'before' screenshot (if I had done what Barney said instead of just pasting):

My description above fixed it on 2 mac's running macOS Big Sur (11.2.3 (20D91).

And if you you see the other thread in the link that is ref the other solutions.

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Answer 4

Apr 7, 2021 12:40 AM in response to Luke__Skywalker

Oh, all my screenshots have not appeared after posting.

Before: was just that we can't access localhost:631 "safari can't the page "localhost:631" because safari can't connect to the server 'localhost'."

Then one at the end showed localhost working.

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Answer 5

Apr 7, 2021 8:50 AM in response to Luke__Skywalker

Luke__Skywalker wrote:

Thanks Barney-15E - yep, I just pasted them in! Doh... I know now, thanks :-)

leroydouglas, I know how to enable the interface, that was not the issue.

My description above fixed it on 2 mac's running macOS Big Sur (11.2.3 (20D91).

Then try this:

Open system preferences.

Go to Security & Privacy > Firewall.

Unlock your padlock with your system password.

Actually I think I unlocked mine at system preferences, then went to firewall?

Then... the technical part, get ready, it's pretty intense:

lock your padlock...

I guess I fail to understand the issue here or the fix as you post —in macOS Big Sur 11.2.3 (20D91)

How exactly does Firewall fit in to your 'fix' ...(?)

System Preferences>Security & Privacy lock by default when you exit.

All I did was simply run the command line to see the CUPS interface in the browser.

please advise...

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Answer 6

etresoft

Level 8

45,870 points

Apr 7, 2021 8:59 AM in response to leroydouglas

leroydouglas wrote:

I guess I fail to understand the issue here or the fix as you post —in macOS Big Sur 11.2.3 (20D91)

How exactly does Firewall fit in to your 'fix' ...(?)

System Preferences>Security & Privacy lock by default when you exit.

All I did was simply run the command line to see the CUPS interface in the browser.

please advise...

I haven't used that CUPS web interface in years. I just tried it in Big Sur and it failed just as predicted. Then I unlocked and re-locked the firewall preference pane and then the interface started working. It actually says that the web interface is disabled, but there was an actual response, not a "not found" error.

For people who do need the CUPS web interface, this would be a useful trick to kick start it going.

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