This article provides a detailed, clear-cut analysis of HTTP/1 vs HTTP/2 vs HTTP/3, focusing on how each version improves (or fails to improve) web performance, efficiency, and modern use cases.

Table of Contents

What is HTTP?

HTTP stands for Hypertext Transfer Protocol. It’s the foundation of data communication on the World Wide Web. When you visit a website, your browser uses HTTP to request content (like text, images, videos) from a server and display it for you.

In simple terms:

HTTP is how your browser and a website’s server talk to each other.
It follows a request-response model: your browser sends a request, and the server sends back a response.

Example:

When you go to https://example.com, your browser sends an HTTP request like:

GET / HTTP/1.1
Host: example.com

The server replies with a response like:

HTTP/1.1 200 OK
Content-Type: text/html ...

Key Concepts:

HTTP Methods: Tell the server what you want to do. Common ones:
GET: Retrieve data
POST: Submit data
PUT: Update data
DELETE: Remove data
Status Codes: Show the result of your request:
200 OK: Success
404 Not Found: Page doesn’t exist
500 Internal Server Error: Server had a problem

Also worth noting:

HTTPS is the secure version of HTTP (adds encryption via SSL/TLS).

HTTP/1.1 (1997)

Key Features

Text-based protocol: Human-readable headers and requests.
Persistent connections: Reuses TCP connections for multiple requests (keep-alive).
Pipelining (optional and flawed): Meant to allow multiple requests without waiting for each to finish, but rarely used due to issues.

Limitations

Head-of-Line (HOL) blocking: One slow request blocks the rest.
No true multiplexing: Only one request per TCP connection at a time.
Inefficient use of TCP: Opens multiple connections per origin to parallelize downloads, which wastes resources.
Compression missing: Headers are repeated with every request, making them bulky.

HTTP/2 (2015)

Key Improvements

Binary protocol: More efficient than HTTP/1.1’s text-based format.
Multiplexing: Multiple requests/responses can happen in parallel over a single TCP connection.
Header compression (HPACK): Reduces overhead from repeated header information.
Stream prioritization: Clients can hint which resources are more important.
Server push: Server can send resources before the browser asks for them.

Remaining Issues

Still tied to TCP: If one packet is lost, all streams over that connection stall due to TCP’s HOL blocking.
Server push underused and complex: It’s often disabled because it can cause unnecessary data transfers.

HTTP/3 (2022)

What’s New

Built on QUIC: Replaces TCP with QUIC (Quick UDP Internet Connections), a transport protocol over UDP.
No Head-of-Line blocking: Each stream is independent, so one lost packet doesn’t block others.
Built-in TLS 1.3: Faster, secure handshakes integrated into the protocol.
Connection migration: Seamless continuation even if a client’s IP address changes (e.g., switching from Wi-Fi to mobile).

Benefits

Faster page loads in poor network conditions: QUIC handles packet loss and network changes better.
Reduced latency: Faster handshakes and no HOL blocking.
More mobile-friendly: Designed for unstable and high-latency environments.

Challenges

Still maturing: Not all networks support UDP well (e.g., some firewalls block it).
Server support: Adoption is growing but not yet universal.