This link shows you the definitions of the warning levels (I’m assuming you are using C# code in your web project). Level 5 is the most strict.
- 0: Turns off emission of all warning messages.
- 1: Displays severe warning messages.
- 2: Displays level 1 warnings plus certain, less-severe warnings, such as warnings about hiding class members.
- 3: Displays level 2 warnings plus certain, less-severe warnings, such as warnings about expressions that always evaluate to true or false.
- 4: Displays all level 3 warnings plus informational warnings. This is the default warning level at the command line.
- 5: Displays level 4 warnings plus additional warnings from the compiler shipped with C# 9.0.
Anything greater than 5 is treated as 5.