Client makes requests to servers for resources like pages or API data
Server sends back responses with status codes like 200 OK, 404 Not Found, 500 Internal Server Error
Requested data is returned in the response body
POST, GET, PUT, DELETE (CRUD)
HTTPS
Builds on HTTP by adding encryption through Transport Layer Security (TLS)
TLS allows the browser and server to establish an encrypted connection to keep data confidential as it travels over the public internet
Traffic is scrambled, so intercepting it is meaningless
TLS also identifies server identify, preventing man-in-the-middle attacks
Overall, TLS provides encryption, security and authentication
HTTP/3
Improves speed and security by fixing performance issues with previous versions
Uses QUIC, built on UDP rather than TCP, optimises performance without TCP overhead
QUIC minimises lag when switching networks on a smartphone
Eliminated head-of-line blocking, where one lost packet stalls stream behind it, where other streams do not wait for the stalled one
Speeds up initial connection setup by combining cryptography and transport handshakes into one action, skipping round trips for servers they have already connected to before (equivalent to TCP + TLS)
Encrypts at the transport layer by default, all connection data is encrypted, not just the application payload, even metadata like packet number
Web Socket
Full duplex bi-directional communication on a single TCP connection, upgrade from HTTP
Enables seamless real-time collaboration and live data streams
Initial WebSocket handshake reuses the existing TCP connection, then messages can flow freely in both directions with minimal framing
Supports sending small messages instantly with very low overhead, ideal for chat, gaming or real time updates
Encryption via TLS is supported for security
TCP
Has reliable transmission, ordered data delivery and congestion control to smoothly exchange messages and keep real-time connections stable
Prioritises delivery over speed through error checking, transmission control and ordered data delivery
Adapts to network conditions with flow control and retransmissions
UDP
Less overhead compared to TCP, but lacks reliability, so HTTP/3 adds checks to prevent corruption (useful for gaming, voice, IOT and streaming)
Focuses on speed an reliability with very lightweight error checking and no handshakes
Can be corrupted by dropped packets
But combining with application-layer integrity checks balances speed and reliability
SMTP
Standard for transferring email messages between mail servers
FTP
Allows efficient uploading and downloading of files between hosts
