Visual Studio Behind Corporate Firewall

Developing in companies that have proxy servers for developers can be frustrating in this age when every tool needs access to online resources and even parts of software development life cycle are cloud based. Proxy servers that require NTLM authentication are one of sources of frustration. NTLM is developed by Microsoft but many applications built by Microsoft do not support it or require some configuration and in worst cases some hacking to make it work. Below are the list of some the tools that developers might be using on a daily basis. I keep adding more to the list as I encounter them.

Visual Studio Code (VSCode)

VSCode 1.15 and up now supports NTLM proxy (finally Microsoft supported its own authentication protocol).


For NPM you have two options. Either to send proxy address and credentials in every single command you run or to set them in the global configuration of NPM. I recommend the former because it is more secure.

Set proxy in every command

When calling NPM command you can always use --proxy switch to set proxy for each command. The syntax for using this switch is the following.

--proxy username:password@proxyaddress:port

For example to use myproxy:8080 as proxy address and my-domain\reza as username and P@ssw0rd as password when calling the install command you can type the following.

npm install --proxy http://my-domain%5Creza:P%40ssw0rd@myproxy:8080

Please note that both username and password are URL encoded. You can use the following command in your browser’s developer tools to encode them.


Set proxy in NPM configuration

To set the proxy in the global configuration of NPM you need use the same format as above for sending the proxy address, username and password and use npm config set to store it in the configuration. For example to set the proxy address to myproxy:8080 and username to my-domain\reza and password to P@ssw0rd you can use the following command.

npm config set proxy http://my-domain%5Creza:P%40ssword@myproxy:8080

Visual Studio, Web Platform Installer and other .NET applications

To set the proxy for pretty much any .NET application, you need to put the following in the configuration file of that application.

    <defaultProxy useDefaultCredentials="true" enabled="true">
        <proxy bypassonlocal="true" proxyaddress="http://myproxy:8080" />

For Visual Studio I suggest also enabling IPV6 if the above configuration did not work as suggested by some other developers.

        <ipv6 enabled="true"/>
    <defaultProxy useDefaultCredentials="true" enabled="true">
        <proxy bypassonlocal="true" proxyaddress="http://myproxy:8080" />

For executable files the configuration file is named the same as executable’s file name but with .exe.config extension. For Visual Studio it is called devenv.exe.config and for Web Platform Installer it is WebPlatformInstaller.exe.config.

Visual Studio Behind Corporate Firewall

How to install/update Atom, Sublime, VSCode and Brackets packages behind corporate proxy (NTLM)

Many developers these days are using these fancy new cross-platform text editors that are lightweight and fast to reduce the workflow of writing and testing code. I’m mostly talking about web developers here. If you are new in this world I suggest you give the followings a shot as after days of researching and trying I think currently they are the bests:

Now back to the subject. Many of these text editors support proxy servers, but none of them that I have tried support NTLM for authentication and if your corporate proxy is using NTLM they simply cannot connect to it. Or lets say not directly! Actually the only solution I have found is to use a software called CNTLM that can act as a proxy server itself and behind the scene it can connect to another proxy server that is using NTLM. The good news is this software is open-source, very lightweight and independent of any external library (written in C) and can take care of all the complexity of NTLM. In fact You can easily setup CNTLM to allow any application that does not support NTLM authentication to connect to the internet. Atom is based on NodeJS (most of them are) so you’ll be able to apply what you will learn hear to other similar text editors as well.

Configure CNTLM to use your corporate proxy

  1. CNTLM is an opensource software and you need to download its latest version from SourceForge website here.
  2. Now you need to install it by running the installation package. There is not much to worry about. it just adds a few shortcuts to your start menu and copies the file under “Program Files (x86)“.
  3. All the settings of CNTLM are stored in Program Files (x86)\Cntlm\cntlm.ini, and you can open this file from Start Menu > Cntlm > cntlm.ini
  4. The cntlm.ini file is quite self descriptive. You just need to add the following lines in this file:
Username    your-username
Domain      your-domain-name
Password    your-password-or-leave-empty
Proxy       proxy-ip-or-hostname:port
Proxy       another-proxy-ip-or-hostname:port
Listen      3128

you can add as many Proxy lines as you want, Cntlm will try them one by one until it can find one that works.

Please note that the address of your proxy will be "localhost:3128" by default but you can change it to any desired port that is not currently being used by another program. You just need to change the value in front of Listen setting. I have highlighted the line so you never miss it.

  1. Star the proxy server by  heading to Start Menu > Cntlm > “Start Cntlm Authentication Proxy”
  2. Test your shiny new proxy by using your favorite browser.

Configure Atom to use Cntlm as proxy server

  1. Start Atom by heading to Start Menu > All Programs > GitHub, Inc > Atom
  2. Go to File > Settings or press Ctrl+Comma. Click on “Open Config Folder” button in the left pane of the Settings tab. It will open and show all the content of the setting folder in Atom.
  3. Click and open .apmrc file located under the root setting folder (.atom folder) and add the following lines:

The last line (that I have highlighted) tells npm to use the http address instead of the default https address. This is because I noticed that Cntl might have some problems with https addresses. This issue might be solved later and you might not need it in the future.

  1. Restart Atom and enjoy using your favorite packages.

A little bonus

By running the following command you can tell many other programs to use your new little proxy server by default. Unfortunately not every program supports it.

netsh winhttp set proxy localhost:3128 "localhost,127.0.0.*"

How to install/update Atom, Sublime, VSCode and Brackets packages behind corporate proxy (NTLM)