Breaking changes in ASP.NET Core 5

If you're migrating an app to ASP.NET Core 5, the breaking changes listed here might affect you. Changes are grouped by technology area, such as ASP.NET Core or cryptography.

[!INCLUDE binary-source-compat]

Title	Binary compatible	Source compatible
ASP.NET Core apps deserialize quoted numbers	✔️	❌
AzureAD.UI and AzureADB2C.UI APIs obsolete	✔️	❌
BinaryFormatter serialization methods are obsolete	✔️	❌
Resource in endpoint routing is HttpContext	✔️	❌
Microsoft-prefixed Azure integration packages removed	❌	✔️
Blazor: Route precedence logic changed in Blazor apps	✔️	❌
Blazor: Updated browser support	✔️	✔️
Blazor: Insignificant whitespace trimmed by compiler	✔️	❌
Blazor: JSObjectReference and JSInProcessObjectReference types are internal	✔️	❌
Blazor: Target framework of NuGet packages changed	❌	✔️
Blazor: ProtectedBrowserStorage feature moved to shared framework	✔️	❌
Blazor: RenderTreeFrame readonly public fields are now properties	❌	✔️
Blazor: Updated validation logic for static web assets	❌	✔️
Cryptography APIs not supported on browser	❌	✔️
Extensions: Package reference changes	❌	✔️
Kestrel and IIS BadHttpRequestException types are obsolete	✔️	❌
HttpClient instances created by IHttpClientFactory log integer status codes	✔️	❌
HttpSys: Client certificate renegotiation disabled by default	✔️	❌
IIS: UrlRewrite middleware query strings are preserved	✔️	❌
Kestrel: Configuration changes detected by default	✔️	❌
Kestrel: Default supported TLS protocol versions changed	✔️	❌
Kestrel: HTTP/2 disabled over TLS on incompatible Windows versions	✔️	✔️
Kestrel: Libuv transport marked as obsolete	✔️	❌
Obsolete properties on ConsoleLoggerOptions	✔️	❌
ResourceManagerWithCultureStringLocalizer class and WithCulture interface member removed	✔️	❌
Pubternal APIs removed	✔️	❌
Obsolete constructor removed in request localization middleware	✔️	❌
Middleware: Database error page marked as obsolete	✔️	❌
Exception handler middleware throws original exception	✔️	✔️
ObjectModelValidator calls a new overload of Validate	✔️	❌
Cookie name encoding removed	✔️	❌
IdentityModel NuGet package versions updated	❌	✔️
SignalR: MessagePack Hub Protocol options type changed	✔️	❌
SignalR: MessagePack Hub Protocol moved	✔️	❌
UseSignalR and UseConnections methods removed	✔️	❌
CSV content type changed to standards-compliant	✔️	❌