HTTP Upgrade Header - HTTP/2
Download List of All Websites using HTTP Upgrade Header - HTTP/2
The HTTP Upgrade mechanism is used to establish HTTP/2 starting from plain HTTP. The client starts an HTTP/1.1 connection and sends an Upgrade: h2c header. If the server supports HTTP/2, it replies with HTTP 101 Switching Protocol status code. The HTTP Upgrade mechanism is used only for cleartext HTTP2 (h2c). In the case of HTTP2 over TLS (h2), the ALPN TLS protocol extension is used instead.
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Vary Header check for User-Agent
Download List of All Websites using Vary Header check for User-Agent
When using the Vary: User-Agent header, caching servers should consider the user agent when deciding whether to serve the page from cache
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Vary Header Accept-Encoding
Download List of All Websites using Vary Header Accept-Encoding
The Accept-Encoding request HTTP header advertises which content encoding, usually a compression algorithm, the client is able to understand. Using content negotiation, the server selects one of the proposals, uses it and informs the client of its choice with the Content-Encoding response header.
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HSTS - Browser HTTPS Only
Download List of All Websites using HSTS - Browser HTTPS Only
The HTTP Strict-Transport-Security response header (often abbreviated as HSTS) lets a web site tell browsers that it should only be accessed using HTTPS, instead of using HTTP for 300 seconds
XFN 1.1
Download List of All Websites using XFN 1.1
XFN is a technical term that is an acronym that stands for “XHTML Friends Network.” This is primarily used by websites that want to create a series of referral links between other websites in order to boost SEO ratings.