# Issues with Download, Installation or Running being Blocked **URL:** \ **Category:** Documentation\ **Created:** [March 31, 2024, 8:31pm UTC](https://forum.vassalengine.org/t/issues-with-download-installation-or-running-being-blocked/79316 "2024-03-31T20:31:29Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![slimy](https://forum.vassalengine.org/user_avatar/forum.vassalengine.org/slimy/32/4448_2.png) [@slimy](https://forum.vassalengine.org/u/slimy)\ **Post date:** [March 31, 2024, 8:31pm UTC](https://forum.vassalengine.org/t/issues-with-download-installation-or-running-being-blocked/79316/1 "2024-03-31T20:31:29Z")
# ![macosx](https://forum.vassalengine.org/uploads/default/original/2X/c/c24d21f1dbd9387b7973e19633ee3e5e1f63f213.png) Mac not being able to verify the Developer On a Mac you may get an error: “VASSAL cannot be opened because the developer cannot be verified. MacOS cannot verify that this app is free from malware.” What you can do to remedy the problem depends a little on the version of MacOS installed on your system. ## Older version of MacOS If you see a dialog like the one below, click _OK_. ![MacOS cannot verify that this app is free from malware.](https://forum.vassalengine.org/uploads/default/original/2X/c/c8d9d8afdbc87978f79e795eeb27f767114acf6c.png) ## Intermediate version of MacOS If you have a more recent version of MacOS, [Gatekeeper](https://support.apple.com/guide/security/gatekeeper-and-runtime-protection-sec5599b66df/web) is probably active – MacOS will block VASSAL from running on the first attempt (because _Vassal_ isn’t what Apple considers a code-signed app). Once you have tried to run Vassal _once_, you can follow the below to remedy the problem. > You’ll have to go into **System Preferences** → **Security & Privacy** to allow it to run. This only needs to be done once.\* 1. _System Preferences_ → Security & Privacy 2. Unlock (if needed) and click _Open Anyway_ 3. Click _Open_ Alternatively you can open a _Finder_ window, type VASSAL into the search field, and double click on your new VASSAL install to open it for the first time - this will give you an “are you sure?” type dialog, and once you are past that then you will be able to open VASSAL normally in the future. ## Relatively new versions of MacOS When you launch Vassal the first time after [installation](https://forum.vassalengine.org/t/installation-instructions/85146), you may see the pop-up dialog ![VassalNotOpened](https://forum.vassalengine.org/uploads/default/original/2X/4/4169fbace37b4a4d67cf2c4dca24874a55329080.jpeg) To get Vassal to run, follow the below procedure (these steps need only be done _once_) 1. Click the **?** button in the top-right of the dialog. 2. This will take you to a help page 3. That will open up the _Settings_ app for you in the _Privacy and Security_ sub-page 4. A new dialog will appear 5. You may be presented with yet another dialog asking you to authorise as system administrator using either a biometric (e.g., finger print) or password. 6. You may also need to give Vassal permissions to access your folders. ### Alternative solution 1 1. Download MacOS disk image (`.dmg`) from the Vassal [the download page](https://vassalengine.org/download.html). 2. Install as per usual - see [here](https://forum.vassalengine.org/t/installation-instructions/85146) 3. Open a Terminal via _Finder_→_Applications_→_Utilities_→_Terminal_ 4. Type in the command line ```auto $ xattr -d com.apple.quarantine /Applications/VASSAL.app ``` and press `Enter`. Voila, you should have removed the [quarantine](https://stackoverflow.com/a/37800961) attribute from Vassal, and you should be able to execute the application as per usual. ### Alternative solution 2 Use the web-client `curl` which is part of MacOS. Follow the steps below: 1. Go to [the GitHub Release](https://github.com/vassalengine/vassal/releases/) page 2. Open a terminal via _Finder_→_Applications_→_Utilities_→_Terminal_ (If you have not used a terminal before, perhaps this solution is not for you. The [terminal](https://support.apple.com/guide/terminal/welcome/mac) is a very powerful tool to interact with the operating system in ways you’ve [never imagined](https://www.macworld.com/article/671711/30-terminal-tips-tricks-and-projects-for-mac.html#23-watch-an-ascii-version-of-star-wars).) 3. Once downloaded, double-click the VASSAL `.dmg` now in your `Downloads` folder, and install per usual instructions - see [here](https://forum.vassalengine.org/t/installation-instructions/85146). ### Explanation MacOS [attaches a quarantine attribute to files downloaded by web browsers](https://stackoverflow.com/a/37800961), which prompts intervention by the Gatekeeper feature. Downloads performed by command line tools like `curl` and `wget` do not have this attribute set. # ![windows](https://forum.vassalengine.org/uploads/default/original/2X/6/6493154fc0bdf2bbf13fe4264cfbd26389f67e37.png) “this file isn’t commonly downloaded” warning On Windows, when downloading a newly-released version of VASSAL with Edge, Chrome, and other browsers, Microsoft SmartScreen may intervene with a warning that the file isn’t commonly downloaded. Respond to these prompts by choosing to keep the file anyway. _Edge warns about the installer download–start by choosing “Keep”._ ![Edge warns about the installer download](https://forum.vassalengine.org/uploads/default/original/2X/6/6b2a19d779016f425dac6f8015807b2fcbb05d0c.png) _On the repeated warning, choose **Keep anyway** to save the download_ ![repeated warning](https://forum.vassalengine.org/uploads/default/original/2X/d/d2da15e27a8ebda2dec38dfac862b9d2f9c75ca5.png) _In Chrome, choose **Keep** to save the download from the warning dialog_ ![In Chrome](https://forum.vassalengine.org/uploads/default/original/2X/2/2061f69f88df10a2e67c5bf2714d03967ec0b4df.png) # ![windows](https://forum.vassalengine.org/uploads/default/original/2X/6/6493154fc0bdf2bbf13fe4264cfbd26389f67e37.png) “Windows protected your PC” when running the installer Windows Defender sometimes blocks VASSAL’s installer from running: “Microsoft Defender SmartScreen prevented an unrecognized app from starting. Running this app might put your PC at risk.” ![Microsoft Defender SmartScreen prevented an unrecognized app from starting. Running this app might put your PC at risk.](https://forum.vassalengine.org/uploads/default/original/2X/9/96608bd7fb816b6ccb49cf32bebb5e85780dab11.png) Windows checks whether executables downloaded from the internet are signed and how often they’ve been downloaded (globally). Our installer is not presently signed, so you may see this message if you try installing VASSAL shortly after a new release. It does not indicate a problem with the installer. _Click More info in the dialog to reveal the **Run anyway** button to run the installer._ ![Click the Run anyway button to continue](https://forum.vassalengine.org/uploads/default/original/2X/1/185e671c1145a5a1bda7e7d422c335195e38fc15.png) # ![windows](https://forum.vassalengine.org/uploads/default/original/2X/6/6493154fc0bdf2bbf13fe4264cfbd26389f67e37.png) Windows Smart App Control blocking installer. See [this post](https://www.xda-developers.com/microsoft-introduces-smart-app-control-toggle-im-turning-it-off/), as well as [this one](https://www.xda-developers.com/smart-app-control-windows-11-finally-worth-turning-on/#how-you-can-turn-smart-app-control-on-or-off), for how to _temporarily_ turn off the Microsoft Smart App checker. # ![windows](https://forum.vassalengine.org/uploads/default/original/2X/6/6493154fc0bdf2bbf13fe4264cfbd26389f67e37.png) Antivirus scanner quarantines the installer Some antivirus scanners (AVG and Avast in particular) mistdetect Vassal’s Windows installers as a threat. The way to fix this problem, both for yourself and for others, is to report the false positives to your AV vendor. (E.g., there is a “Report as false positive” link in the screenshot from AVG shown here.) ![AVG "Threat secured" dialog](https://forum.vassalengine.org/uploads/default/original/2X/8/8d95b15b5d9bffeabcef5848f79858da72dc6167.jpeg) If you want to verify that your installer is the installer we released, you can check the SHA256 hash of your installer file against the list we publish. (If you need a tool for computing the SHA256 hash of the installer file you have, a simple solution is to try uploading the file to [VirusTotal](https://www.virustotal.com/gui/home/upload), which will compute the file’s SHA256 hash and display it.) ![SHA256 hashes are published with each release](https://forum.vassalengine.org/uploads/default/original/2X/9/9acd49cc1ffabdec9ec0586fba748e8fb56c8aa7.png) ---
**Author:** ![adamevois](https://forum.vassalengine.org/letter_avatar_proxy/v4/letter/a/ed8c4c/32.png) [@adamevois](https://forum.vassalengine.org/u/adamevois)\ **Post date:** [March 20, 2026, 1:23am UTC](https://forum.vassalengine.org/t/issues-with-download-installation-or-running-being-blocked/79316/3 "2026-03-20T01:23:38Z")
@[fnf](https://fnf-games.io/) If Gatekeeper is blocking it, try opening VASSAL once with right click and choose Open, then confirm in Security & Privacy if prompted. That usually works without disabling protections completely. ---
**Author:** ![cholmcc](https://forum.vassalengine.org/user_avatar/forum.vassalengine.org/cholmcc/32/8319_2.png) [@cholmcc](https://forum.vassalengine.org/u/cholmcc)\ **Post date:** [March 20, 2026, 12:58pm UTC](https://forum.vassalengine.org/t/issues-with-download-installation-or-running-being-blocked/79316/4 "2026-03-20T12:58:22Z")
> [@adamevois](#): > > That usually works without disabling protections completely. Just to be clear: The two methods either downloading via `curl` or some other utility, or `xattr` on MacOSX _does not_ disable protections completely - only for Vassal. Also, the method of going through the GUI does the same as the `xattr` method. ~~@adamevois - if you have screenshots that illustrate the procedure on a relatively new MacOSX machine, please consider to post them so that we can add it to the main body of the article.~~ Yours, _Christian_