Feed Delta Updates

Nobody asked about any of this, but I assume that at least some of you would be curious about this stuff. Feed delta updates is a defacto standard based on RFC 3229 Delta encoding in HTTP with the feed extension. With delta updates to feeds, your syndication feeds will only return new or modified content to supported feed reader clients instead of giving them the entire feed including old entries they’ve already retrieved. This reduces the bandwidth requirements as your feed will contain fewer posts when the feed reader client have already received the most recent version of an item in your feed.

You can’t really control this as it’s up to the feed reader client and user preferences. You can, however, use the Cache-Control: max-age=<seconds> header to provide a hint to clients as to how often they should be checking for new content. Use the Cache-Control plugin to configure this header.

Atom, RSS, RDF, and anything else WordPress core classifies as a “feed format”.

Quite a few including FeedHQ, Feed Notifier, Internet Explorer, Jarr, Liferea, Microsoft Outlook, Miniflux, Newsblur, Newsbeuter, Vienna, and others. Please make sure you’re running an updated version of your feed reader.

You can use your web browser’s developer tools, or a web utility for inspecting headers like Redbot to request your public feed address. Be sure to include a A-IM: feed header as well as a If-Modified-Since: <rfc-1123-date> header. The plugin will work with any web browser, server-side caching systems, content distribution system, web performance boosters, and other caching infrastructure that correctly implements HTTP caching in a standards compliant way. If your infrastructure supports the Cache-Control: and Vary: headers along with at least one of Last-Modified: or ETag: you shouldn’t have any trouble.

Not as of version 0.9, but this may be supported in the future. Only post feeds (main feed, and feeds for sections, tags, and author pages) is supported.

Not at all. Quite the opposite! This plugin improves on WordPress’ cache handling for feed delta updates and regular feeds alike. The biggest gains are with feed reader clients that support delta updates of feeds, but other feed reader clients will get fewer “false positives” (meaning they download the entire feed even when there is no new posts) when using this plugin.

Quite the contrary! It’s know to have positive effects on PHP processing time compared to the WordPress core feed delivery and feed caching system. As the plugin delivers smaller feeds at a faster rate, it can even free up server resources for other — less efficiently delivered — types of content.

It should, but I can’t test all the tens of thousands of plugins in the WordPress Plugin Directory.

Wow. Thank you for your interest in this plugin! Be sure to check the list of known issues, and the support forum as well. The plugin developer is happy to answer your questions in the forum.