HTTP Versions and Headers

HTTP Versions

HTTP/0.9

RFC: This version was not officially published in an RFC but was experimental.

Features: Very basic, only for sending text content (<text/html>) and receiving simple responses. Requests could only be made using <GET>, and there was no way to send data to the server.

HTTP/1.0

RFC: RFC 1945

Features: The first official version of HTTP, supporting <POST> requests for sending data to the server. It included headers for controlling content type, language, and cache management. Each HTTP request required a separate connection.

HTTP/1.1

RFC: RFC 2616 (and newer versions RFC 7230 to 7235)

Features: Included several improvements and new features:

• Persistent Connections: Allows multiple requests and responses over a single TCP connection.
• Chunked Transfer Encoding: Allows sending large responses in chunks.
• Improved Cache Management: New headers for better cache control.
• New Methods: Support for methods like <PUT> and <DELETE>.
• Enhanced Error Handling: New status codes for better error management.

HTTP/2

RFC: RFC 7540

Features: Major improvements over HTTP/1.1 including:

• Multiplexing: Multiple requests and responses over a single TCP connection.
• Compression: Header compression to reduce data size.
• Stream Prioritization: Allows prioritizing requests to improve page load performance.
• Binary Protocol: Uses a binary protocol instead of text for improved efficiency.

HTTP/3

RFC: RFC 9114

Features: The latest version with the following features:

• QUIC Protocol: Uses QUIC instead of TCP to improve latency and performance.
• Multiplexing and Stream Prioritization: Similar to HTTP/2 but enhanced with QUIC.
• Reduced Latency: Improved latency and reduced page load times.

HTTP Headers by Version

HTTP/1.0 Headers

Headers introduced in HTTP/1.0:

• Accept
• Accept-Charset
• Accept-Encoding
• Accept-Language
• Authorization
• Cache-Control
• Connection
• Date
• Expect
• From
• Host
• If-Match
• If-Modified-Since
• If-None-Match
• If-Range
• If-Unmodified-Since
• Max-Forwards
• Pragma
• Proxy-Authorization
• Range
• Referer
• TE
• Upgrade
• User-Agent
• Via

HTTP/1.1 Headers

Headers introduced in HTTP/1.1:

• Accept-Patch
• Accept-Ranges
• Age
• Allow
• Content-Encoding
• Content-Language
• Content-Length
• Content-Location
• Content-MD5
• Content-Range
• Expires
• Forwarded
• If-None-Match
• Last-Modified
• Link
• Location
• Proxy-Authenticate
• Retry-After
• Server
• Vary
• WWW-Authenticate

HTTP/2 Headers

Special pseudo-headers used in HTTP/2:

• :authority
• :method
• :path
• :scheme
• :status

HTTP/3 Headers

HTTP/3 headers are similar to HTTP/2:

• :authority
• :method
• :path
• :scheme
• :status