SPDY only runs encrypted. The HTTP&#x2F;2 specification allows it to run without encryption <a href="https:&#x2F;&#x2F;http2.github.io&#x2F;faq&#x2F;#does-http2-require-encryption" rel="nofollow">https:&#x2F;&#x2F;http2.github.io&#x2F;faq&#x2F;#does-http2-require-encryption</a> But most of the browser vendors will only allow to use it with encryption (see footnotes here): <a href="http:&#x2F;&#x2F;caniuse.com&#x2F;#search=http%2F2" rel="nofollow">http:&#x2F;&#x2F;caniuse.com&#x2F;#search=http%2F2</a>