How Much Faster Does HTTP/2 Actually Make Your Site?
HTTP/1.1 can only handle one request-response cycle per connection at a time, and most browsers cap connections at 6 per domain. If a page has 60 resources, the browser has to send them in batches of 6, so total load time scales with the round-trip time (RTT) multiplied by the number of batches. This is commonly called head-of-line blocking, and it gets worse as resource count and network latency both increase.
HTTP/2, by contrast, multiplexes many requests and responses over a single TCP connection. Because there's no per-connection queue to wait behind, most responses can theoretically arrive within a single round trip regardless of resource count. This calculator models that difference in a simplified way, and you'll see the improvement grow larger as resource count and RTT increase.
Real-world results also depend on server bandwidth, TLS handshake behavior, and resource prioritization, so treat this as a directional estimate rather than an exact number. If your site already has few resources or relies heavily on a CDN and caching, the practical gain from switching to HTTP/2 may be smaller than the raw math suggests.
Frequently Asked Questions
HTTP/2 multiplexes many requests over a single connection, largely eliminating the queuing that HTTP/1.1 suffers from due to its per-domain connection limit.
Most browsers cap connections at 6 per domain, so if a page has more than 6 resources, the rest have to wait for an existing connection to free up.
The gain can be small on sites with few requests or already well-optimized, but it grows significantly with more resources and higher latency.