If anything goes wrong, you can revert back to the "Automatic Proxy settings" in System Network Preferences using Automatic Proxy Configuration your-corporate-proxy-uri:port-number/proxy.pac
In order to run this in the local iOS Simulator while on your corporate wi-fi network, a local proxy manager is required. This local proxy application, named Charles, is what our iOS Dev Team uses. Meet Charles, get to know him. He is your friend.
Open Mac OS Network Preferences
Open System Preferences for your Mac (Apple Menu > System Preferences).
Go to Network.
Be sure your Location is set to your proxy network, and not "Automatic".
With Wi-Fi selected on the left and/or ethernet connection, click Advanced... on the bottom right side of the window.
Configure Proxy Address
Disable/uncheck "Automatic Proxy Configuration" if it is set.
Check "Web Proxy (HTTP)" and set "Web Proxy Server" to 127.0.0.1 : 8888
Check "Secure Web Proxy (HTTPS)" and set "Secure Web Proxy Server" to 127.0.0.1 : 8888
If it asks, don't allow it to manage your Mac OS Network Configuration, the previous steps do that. (If you change Charles port, update the previous step to the correct port instead of default 8888)
In the menu of Charles go to Proxy > External Proxy Settings, check Use external proxy servers
Check Web Proxy (HTTP), and enter your-corporate-proxy-uri:port-number
Check Proxy server requires a password
Domain: YOUR DOMAIN, Username: YOUR USERNAME Password: YOUR PASSWORD
Same for Secure Web Proxy (HTTPS). Be sure to fill in the same proxy, username, and password address fields.
In the text area for Bypass external proxies for the following hosts: enter
You may need to include your mail server, or other corporate network addresses.
Check "Always bypass external proxies for localhost"
iOS Simulator Configuration
If you have an existing iOS Simulator custom setup going that is not working, "Simulator > Reset Content and Settings" from the menu.
If you have the Simulator open still, quit it.
Now, in Charles under the "Help" menu > Install Charles Root Certificate, and then again for Install Charles Root Certificate in iOS Simulators
Technical note: This whole process is required because the iOS Simulator is served a bum proxy certificate instead of the actual certificate, and doesn't allow it, for https://exp.host/ which is required to run Expo.
Also note: Configure applications that need internet access, such as Spotify, to use http://localhost:8888 as your proxy. Some apps, such as Chrome and Firefox, you can configure in the settings to use your "System Network Preferences" which will use Charles : 8888, or no proxy, depending on how you have your "Location" set in the Apple menu / network preferences. If you are set to "Automatic" no proxy is used, if it is set to "your proxy network" the proxy is used and Charles will need to be running.
Command line application proxy configuration
npm, git, Brew, Curl, and any other command line applications need proxy access too.
Note: if you switch your network location back to "Automatic" in order to use npm or git, you will need to comment these lines out using a # before the line you wish to disable. You could alternatively use a command-line proxy manager if you prefer.