What Are HTTP Content Types And Why They Matter

The aim of this explainer💡 is to define content types for HTTP protocol

1. instructions

• when you enter URL you typically want to view/access a resource
• in order for a host to properly serve a resource + in order for a client to properly display a resource:
• we need a specification of a resource type: .jpg image should not be rendered as text
• for this reason, host responds with content types within the header of the HTTP message

<!-- SYNTAX -->
<primary_type>/<sub_type>
application/json

• this depends on MIME standards: Multi-purpose Internet Mail Extensions
• originally this standard was designed for for email, but HTTP uses the same labels
• content types are configured on web server such as IIS
• there is a mapping between a file extension and MIME type
• after mapping, web server serves content type in a content-type header
• for browser, this is the first-place to look to understand what it is receiving (not! file extension)
• browsers will do MIME sniffing in some cases and will not necessarily follow the value of this header
• to prevent this behavior, the header X-Content-Type-Options can be set to nosnif
• if requests (such as POST or PUT) include content-type headers, the client tells the server what type of data is actually sent in its body