X-Content-Type-Options
X-Content-Type-Options is an HTTP response header that controls whether clients may perform MIME-type sniffing.
Building Web APIs with ASP.NET Core
An HTTP response header that prevents browsers from interpreting content as a type different from its declared media type.
- How it is used
- Hardens deployed web API responses against content-type confusion and potentially harmful file handling.
- How deep it goes
- Defines the header’s protection and shows its middleware configuration, but defers detailed security-header coverage.
- Examples
- Uses Program.cs middleware to add X-Content-Type-Options with the value "nosniff" outside development.
- What you can do after
- Operate/configure an API response pipeline that emits the nosniff protection header in deployed environments.
Read how Building Web APIs with ASP.NET Core explains X-Content-Type-Options →
ASP.NET Core in Action, 3e
X-Content-Type-Options is an HTTP response header that controls whether browsers may perform MIME-type sniffing.
- How it is used
- Adds a browser security header to every ASP.NET Core response, including static files, errors, and Razor Pages.
- How deep it goes
- Explains the header value and response-timing middleware, but does not detail MIME-sniffing internals.
- Examples
- Uses app.Use, Response.OnStarting, next(), and the nosniff header assignment as the working implementation.
- What you can do after
- Apply it via ASP.NET Core middleware to attach nosniff reliably before responses begin streaming.
Read how ASP.NET Core in Action, 3e explains X-Content-Type-Options →
Related concepts
- HTTP headerkind of · An HTTP header is a named metadata field in an HTTP request or response that conveys information about the message or directs its processing.
- cross-site scripting attackaddresses · Cross-site scripting is a web security vulnerability in which attacker-controlled content causes executable script to run in another user’s browser within a trusted application context.
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