HTTP/2

Learning Focus

By the end of this lesson you will understand what HTTP/2 improves over HTTP/1.1, how to enable it in OpenLiteSpeed, and how to verify it is active.

What HTTP/2 Improves

Feature	HTTP/1.1	HTTP/2
Requests per connection	One at a time	Multiplexed (many simultaneously)
Header handling	Text, repeated per request	Binary, compressed (HPACK)
Server push	Not available	Server can push assets proactively
Requires HTTPS	No	Practically yes (browsers require it)

Enabling HTTP/2

HTTP/2 is enabled at the SSL listener level in OpenLiteSpeed:

1. Navigate to Listeners → SSL listener → SSL tab
2. Set Enable HTTP/2 to Yes
3. Save and Graceful Restart

info

HTTP/2 only works over HTTPS. If you do not have an SSL listener configured, set that up first.

Verifying HTTP/2

# Check protocol negotiation
curl -sI --http2 https://example.com | head -1
# Expected: HTTP/2 200

# Or use openssl
openssl s_client -connect localhost:443 -servername example.com -alpn h2 < /dev/null 2>/dev/null | grep "ALPN"
# Expected: ALPN protocol: h2

Key Takeaways

• HTTP/2 multiplexes requests over a single connection — no more head-of-line blocking.
• It is a strong default for most HTTPS sites — enable it on all SSL listeners.
• Verify with curl --http2 or openssl ALPN negotiation.

What's Next

• Continue to HTTP/3 (QUIC) for the next-generation protocol.