HTTP 413 - Request Entity Too Large cheat sheet - asp.net-mvc

Question

I am trying to upload a large file to my ASP.net core/ASP.net mvc site, but keep on encountering HTTP 413 - request entity too large. Even when I try to update web.config, other things still break.
Does anyone have a cheat sheet for dealing with this?

Answer 1

I created an asp.net mvc application and tried to test it.
Often we only pay attention to the uploadReadAheadSize setting, but tests have proved that this cannot completely solve the problem, and there are other configurations that need to be configured. (Added based on Jack's answer)
In addition to setting the uploadReadAheadSize value larger, there are also maxAllowedContentLength and maxRequestLength. You need to modify all these three values, otherwise the 413 or Maximum request length exceeded error will still be displayed.
In my test results, the application can upload any type of file within 1GB.

Answer 2

This works for me. Set it in your web.config under the configuration section:
<system.webServer>
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="999999999" />
</requestFiltering>
</security>
</system.webServer>

Answer 3

Here is my cheat sheet:
The max file size limit coming through from IIS is specified through the UploadReadAhaead parameter, which can be specified in web.config as so. In this case, the maximum is set to 1000485760 bytes
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<system.webServer>
<httpErrors errorMode="Detailed"></httpErrors>
<serverRuntime uploadReadAheadSize="1000485760" />
<httpErrors errorMode="Detailed" />
<asp scriptErrorSentToBrowser="true"/>
</system.webServer>
<system.web>
<customErrors mode="Off"/>
<compilation debug="true"/>
</system.web>
</configuration>
This is grand, as long as this specifier actually works. You might need a different solution, say, if you are hosting locally with something other than IIS (like kestrel, or even IIS express.)
Sometimes this configuration section is locked as well, in which case it can be unlocked using the following command (run cmd as admin):
%windir%\system32\inetsrv\appcmd.exe unlock config -section:system.webServer/serverRuntime
This is also something to consider when setting up prod. In some cases, your configuration within web.config within your code for the uploadReadAheadSize can conflict with whatever is specified in your prod instance. For me, I ended up getting rid of my configuration within source control, and instead, set the uploadReadAhead value for prod during environment set up. I did this by running the command (in cmd as admin):
appcmd set config "https://example.com" /section:system.webserver/serverruntime /uploadreadaheadsize:500048576 /commit:apphost
appcmd set config "http://example.com" /section:system.webserver/serverruntime /uploadreadaheadsize:500048576 /commit:apphost
I also set uploadReadAheadSize within C:\inetpub\wwwroot\web.config on the prod server as well, so it looks something like:
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<system.webServer>
<serverRuntime uploadReadAheadSize="500485760" />
<!--If this line breaks, unlock the config by opening cmd as admin and running %windir%\system32\inetsrv\appcmd.exe unlock config -section:system.webServer/serverRuntime-->
</system.webServer>
</configuration>
This can also be set as per this screenshot:
[![enter image description here][1]][1]
Now that you've set this up, it's still entirely possible that your application breaks, giving you a 413 because even though IIS may be set up correctly, there are also upload limits within the .net core ecosystem which can throw an HTTP 414 error when handling large files. This is something I found out [here][2]
The TLDR of this is that you want to have the following code within your startup.cs -> configureServices()
services.Configure<IISServerOptions>(options => {
options.MaxRequestBodySize = int.MaxValue;
});
services.Configure<FormOptions>(x =>
{
x.ValueLengthLimit = int.MaxValue;
x.MultipartBodyLengthLimit = int.MaxValue;
x.BufferBodyLengthLimit = int.MaxValue;
x.MultipartBoundaryLengthLimit = int.MaxValue;
});
Note that there is code in there for if you are hosting for kestrel rather than IIS, also
[1]: https://i.stack.imgur.com/yLHQQ.png
[2]: https://github.com/dotnet/aspnetcore/issues/20369#issuecomment-607057822