| Feature | HTTP/1.0 | HTTP/1.1 | HTTP/2 | HTTP/3 |
|---|
| Introduction Year | 1996 | 1997 | 2015 | 2022 |
| Connection Handling | One request per connection | Persistent connections (keep-alive by default) | Multiplexing over a single connection | Multiplexing over QUIC (UDP-based) |
| Header Compression | None | None | HPACK (binary header compression) | QPACK (optimized for QUIC) |
| Multiplexing | No | No | Yes (over a single TCP connection) | Yes (over QUIC, eliminates head-of-line blocking) |
| Head-of-Line Blocking | Severe | Severe | Reduced (still present at TCP layer) | Eliminated (QUIC-based transport) |
| Security | No native support | No native support | TLS 1.2 or higher (optional) | TLS 1.3 (mandatory with QUIC) |
| Request/Response Model | Text-based, synchronous | Text-based, synchronous | Binary framing, asynchronous | Binary framing, asynchronous |
| Performance | Limited | Improved via pipelining and caching | Faster (multiplexing, fewer connections) | Fastest (QUIC-based improvements) |
| Error Recovery | Basic | Basic | Limited to TCP retries | Better (QUIC’s built-in retransmissions) |
| Connection Type | TCP | TCP | TCP | QUIC (UDP-based) |
| Caching | Basic headers (Expires) | Enhanced headers (Cache-Control, ETag) | Same as HTTP/1.1 | Same as HTTP/1.1 |
| Upgrade Path | New connections required | New connections required | Uses ALPN to negotiate upgrade | Native protocol, no need for upgrade |
