HTTP header size limit setting The size setting is defaulted to 32768, which can be adjusted. The size can be set in Configuration Manager (directly in Infoport) on the Urls tab at the very bottom Or by directly editing appsettings.json in "Kestrel": { "Limits": { "MaxRequestHeadersTotalSize": 32768 }, Increase the value carefully, a multiple times larger limit can be counterproductive and cause problems elsewhere.