Cloudflare has shipped support for the HTTP Vary header in Cache Rules, allowing developers to control how caches handle responses that vary based on request headers like Accept or Accept-Language. The Vary header tells intermediary caches which request fields may affect a response, but without proper handling can create excessive cache entries; Cloudflare's solution lets origins declare what may vary while giving administrators control over how much variation is actually meaningful.
HTTP range requests allow clients to request partial content from servers, useful for media players, download managers, and data tools. Servers indicate support via the Accept-Ranges header, and clients can specify ranges using the Range header, receiving a 206 Partial Content response. Multiple ranges can be requested simultaneously in a multipart response, with the If-Range header ensuring the resource hasn't been modified since the last fragment.
A web crawler named lawa discovered significant HTTP header inconsistencies across millions of requests, including variable capitalization patterns, frequent misspellings in headers with limited valid values, and numerous security issues such as exposed RFC 1918 addresses and request header echo-back vulnerabilities that revealed other crawlers' IP addresses.