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On Mac OS X, when I run Firefox (and Thunderbird, and ...) which I downloaded from Mozilla, the OS pops up a warning that the file was downloaded over the internet, giving the date on which it was downloaded. I have no problem with that warning on the first time I use a downloaded application - but the repeated warnings are a nuisance.

Is there a way to suppress that dialogue box?

Is there a way to avoid it appearing in the first place? (Some applications I download from a corporate intranet - those don't produce the equivalent warning; any idea what the criteria are for when the warning is generated?)

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That's kind of odd. I've never seen that warning show up more than once for a file. –  Herms Sep 9 '09 at 20:56
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7 Answers

up vote 8 down vote accepted

To remove the quarantine alert you can run the following command in Terminal:

xattr -d com.apple.quarantine /PATH/TO/APPLICATION

You may need to run this is an administrator depending on the permissions on the resulting application (as you said you don't run as administrator). If the application has permissions set that you can't remove the metadata with your user account it explains why it comes up every time. You can either run it as an administrator on your computer or run the command above as an administrator. (Use su admin_name if necessary)

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I found another way to get rid of the warning - install the next release of the software as administrator, after downloading it as administrator (Firefox 3.5.3). However, that is a pure evasion of the problem. This command does the trick. However, it does not seem to be well documented - at least, I didn't find a man page for it (but I can STFW and 'xattr -:' gives sufficient info). Thanks! –  Jonathan Leffler Sep 13 '09 at 4:04
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To stop this from happening in the future, go to Terminal and type this (hitting Return afterwards):

defaults write com.apple.LaunchServices LSQuarantine -bool NO

Or — simpler yet — download Secrets and search for “quarantine.”

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Tip via MacWorld. –  Alan H. Dec 25 '10 at 0:22
    
Thanks for the Secrets URL. –  Jonathan Leffler Dec 25 '10 at 0:37
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http://www.macosxhints.com/article.php?story=20071029151619619

A Vista-esque feature of OS X 10.5 is that it tags web downloads (not just those from Safari) as such, and then warns you about running downloaded apps. Archived (e.g. zipped) files inherit the tags from their tagged container.

Link is to discussion of issue and a few scripts and C++ strings you can run to change the behavior permanently.

Not sure if these are going to work with 10.6

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Tracing through the comments, some are definitely relevant to my scenario. I mainly work as a user without System Admin privileges; I download stuff as my normal user. When it comes to installing stuff into /Applications, I sometimes use the option to provide an administrator ID and password on the fly, and sometimes switch to the administrator ID and run the install. I'm also suspicious that the difference may be between the applications than have a package installer you run compared with the applications that you click on the DMG and copy direct to /Applications. The link is good - thanks. –  Jonathan Leffler Sep 9 '09 at 22:32
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Please provide some details regarding what the link includes and what it is posted for. SU is a canonical site and just a link which may disappear over time is not a sufficient answer. –  Diago Sep 12 '09 at 19:41
    
FWIW: the article shows how to write an AppleScript script that will run "xattr -d com.apple.quarantine" on the newly downloaded item. It places the script with the appropriate name in the appropriate location so that the unquarantine operation happens 'automatically'. The article (tagged 10.5 only, but meaning 10.5 or later) is still there today. –  Jonathan Leffler Sep 6 '11 at 15:24
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Late to this question, but here is a method for removing the warning from previously downloaded files, as well as a method for disabling the warning for future downloads:

http://www.macworld.com/article/145324/2010/01/filewarnings.html

* OBLIGATORY WARNING ABOUT DISABLING WARNINGS ON DOWNLOADED FILES *

Apple puts that warning there for a reason, so disable it at your own risk...

Atg

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If there's a file named com.apple.DownloadAssessment.plist in your user's Library/Preferences folder, it will override the global defaults for which files Safari considers "safe." You can also use this technique to make currently-safe files treated as unsafe. In fact, there are four different top-level risk categories:

  1. LSRiskCategorySafe - Auto-opened after download, if Safari has this option enabled.
  2. LSRiskCategoryNeutral - A neutral file won't be auto-opened, but there won't be a warning about its contents, either.
  3. LSRiskCategoryUnsafeExecutable - All executable files fall into this category, and you'll see a warning when you attempt to download one in Safari, Mail, etc.
  4. LSRiskCategoryMayContainUnsafeExecutable - This covers 'container' formats such as disk images and archives. If Safari/Mail can see the contents of the container and determine they're all safe, then no warning will be generated.

For full information, I refer you to this page.

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I don't have the ~/Library/Preferences/com.apple.DownloadAssessment.plist file. I don't know whether it matters that I used Firefox rather than Safari to download the files. –  Jonathan Leffler Sep 9 '09 at 22:18
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This has been an intermittent problem since this question was first posed here, but with Lion it has become commonplace. After a restart of the OS the "quarantine" question will be asked again. Once answered it will not be asked until the next restart.

It's clearly a bug. I suspect it occurs when cautious/smart users run as a non-admin user. It may be related to doing the initial install from the admin account.

We can either live with the bug until it's fixed (not a bad solution) or, if you really can't stand it, I prefer this fix for Lion (example of app shown here) -

OS X should have flagged after you clicked open. You can remove the quarantine flag manually. Open Terminal and paste the following command:

sudo xattr -r -d com.apple.quarantine {,~}/Library/PreferencePanes/Screens\ Connect.prefPane/Contents/Resources/ScreenSync.app
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You need write privileges to remove the quarantine flag from the file. No bug, no nothing. Maybe careless developers who should put this into the application's setup, but that's it. Run once as user with write privileges, and you're good. –  Daniel Beck Sep 6 '11 at 14:06
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Building off of something in the answer from Chealion above I found a simpler solution (that worked for me) that didn't require that I disable all warnings.

This from Chealion:

If the application has permissions set that you can't remove the metadata with your user account it explains why it comes up every time. You can either run it as an administrator on your computer or run the command above as an administrator. (Use su admin_name if necessary)

So instead of running the command from Chealion just changed the ownership of the application that was causing problems using "chown"

chown username \Applications\ApplicationName.app

this issue seemed to be caused by an application that was installed by an administrator when imaging my computer. After I changed ownership the warning didn't reappear.

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