Click on the "name header" of the outbound rules listing to sort the listing alphabetically.
Tap on the Windows-key, type Windows Firewall select the "Windows Firewall with Advanced Security" (in newer versions of Windows 10 "Windows Defender Firewall with Advanced Security") result, and hit enter.
You may need to block "cortana" instead, but that may affect the functionality of the digital assistant as well. Note: Search is listed as an option in stable builds, but most recent Insider Builds don't seem to have that entry anymore. If you open the firewall configuration, you will notice that a Search rule is set there already which you just need to disable. What you may do instead for now is block access to Search using the Windows Firewall.
Some users have stated that this option becomes only available if Cortana is set to off.
Scroll down until you find "Search online and include web results" listed there as an option.
Locate the settings icon on the left of the search interface and click on it.
Run a search by tapping on the Windows-key and starting to type.
Probably the easiest option of the four methods to disable web search in Windows 10. The following method does not work anymore. Update: Microsoft removed the option to disable web searches in the Settings UI.
If it does not exist, right-click on Windows Search and select New > Dword (32-bit) Value, name it ConnectedSearchUseWeb, and set its value to 0.
If the preference ConnectedSearchUseWeb exists, double-click on it and set it to 0 to turn web search in Windows 10 off.
If the key does not exist, right-click on Windows and select New > Key, and name it Windows Search.
Navigate to the following key: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Windows Search.
Tap on the Windows-key, type regedit.exe and hit enter.
The following method is useful to Windows 10 Home users who don't have access to the Group Policy Editor. This method worked in earlier builds of Windows 10 and it is very likely that it will work in newer builds as well.
Locate "Don't search the web or display web results in Search over metered connections" and double-click it.
Locate "Don't search the web or display web results in Search and double-click it.
Locate "Do not allow web search" and double-click it.
Browse to the following path using the left sidebar: Local Computer Policy > Computer Configuration > Administrative Templates > Windows Components > Search.
If you run home, check out the other methods listed below instead. Note that the editor is (likely) only included in Pro and Enterprise versions and not in Windows 10 Home.
To open the Group Policy Editor, tap on the Windows-key, type gpedit.msc and hit enter.