Foundations Recommended Updated 2026-05-29

Feed content hygiene

If you publish a feed, ship it well-formed. Identify the feed inside itself with atom:link rel="self", give every item a stable guid, declare an update cadence with the Syndication module, and validate before deploy.

What it is

Feed discovery tells the world where your feed is. Feed hygiene is about whether the feed itself is well-formed once they fetch it. Aggregators, feed readers, and AI agents all behave better — and waste fewer of your bytes — when the channel identifies itself, every item has a stable identifier, and the publishing cadence is declared.

The conventions are old and stable. The base specs are RSS 2.0 (RSS Advisory Board), RFC 4287 (Atom), and JSON Feed 1.1. The practical layer — what makes a feed actually portable — lives in the RSS Best Practices Profile, which both the W3C Feed Validation Service and the RSS Validator use to flag warnings.

Why it matters

Self-identification (atom:link rel="self") makes a feed portable. If the feed is mirrored, cached, or sent to you by a friend, every reader can still find the canonical subscription URL.
Stable, unique <guid> lets aggregators detect updates without re-displaying old items. Get this wrong and every refresh re-floods subscribers with duplicates.
sy:updatePeriod and sy:updateFrequency tell polite aggregators how often to poll. A weekly blog declaring daily cadence wastes bandwidth on both sides; declaring hourly invites unnecessary load.
<lastBuildDate> lets a reader skip parsing when nothing has changed.
Paging headers (RFC 5005) keep archive feeds usable. Without rel="next"/rel="prev", anything past the first page is invisible to readers that follow links.

The cost of getting these right is one-time and small. The cost of getting them wrong shows up as duplicate posts in every reader, weeks of stale entries, or 100× more polling traffic than you intended.

How to implement

Declare the Atom and Syndication namespaces on the <rss> root, then ship a self-link, channel metadata, and per-item GUIDs:

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0"
     xmlns:atom="http://www.w3.org/2005/Atom"
     xmlns:sy="http://purl.org/rss/1.0/modules/syndication/">
  <channel>
    <title>Example — Posts</title>
    <link>https://example.com/</link>
    <description>Engineering writing from the Example team.</description>
    <language>en-GB</language>

    <atom:link href="https://example.com/feed.xml"
               rel="self" type="application/rss+xml" />
    <lastBuildDate>Mon, 27 May 2026 09:00:00 GMT</lastBuildDate>
    <sy:updatePeriod>daily</sy:updatePeriod>
    <sy:updateFrequency>1</sy:updateFrequency>

    <item>
      <title>Shipping the new search</title>
      <link>https://example.com/blog/new-search/</link>
      <guid isPermaLink="true">https://example.com/blog/new-search/</guid>
      <pubDate>Mon, 27 May 2026 09:00:00 GMT</pubDate>
      <description>Why we rebuilt search on Pagefind.</description>
    </item>
  </channel>
</rss>

Key points:

atom:link rel="self" must point at the canonical URL of the feed itself. Both feed validators flag its absence as a warning.
<guid isPermaLink="true"> is the simplest correct form when the URL never changes. If the URL is unstable, use isPermaLink="false" with a tag URI: <guid isPermaLink="false">tag:example.com,2026:post/123</guid>. Once chosen, the GUID for an item must never change — that is the identifier readers key off.
sy:updatePeriod accepts hourly, daily, weekly, monthly, yearly. sy:updateFrequency is a positive integer (count per period). A site updating twice a day declares <sy:updatePeriod>daily</sy:updatePeriod><sy:updateFrequency>2</sy:updateFrequency>.
Dates use RFC 822 format (Mon, 27 May 2026 09:00:00 GMT). Atom uses RFC 3339.
For archive feeds, add RFC 5005 paging:

<atom:link rel="next" href="https://example.com/feed.xml?page=2" />
<atom:link rel="last" href="https://example.com/feed.xml?page=14" />

Atom and JSON Feed have direct equivalents for all of the above — JSON Feed’s feed_url is the self-link, and its id per item is the GUID.

Common mistakes

Missing atom:link rel="self". Both validators warn on it, and most production feeds in the wild still don’t ship it.
Generating a fresh GUID per build instead of per item. Every reader re-floods subscribers on every deploy.
Mismatched dates — pubDate newer than lastBuildDate, or per-item timestamps in the future. Some aggregators silently drop the item.
Declaring a cadence (<sy:updatePeriod>hourly</sy:updatePeriod>) the site does not actually meet. Aggregators back off if the feed is stale relative to the declared cadence.
Putting absolute URLs in <link> but relative URLs in <atom:link rel="self">. Both should be absolute.
Forgetting xmlns:atom or xmlns:sy namespace declarations. The elements are then technically invalid in RSS 2.0.

Verification

Paste the feed URL into validator.w3.org/feed — expect a clean pass.
Paste it into rssboard.org/rss-validator — the second-opinion validator catches things the W3C one misses.
curl -s https://example.com/feed.xml | grep -i 'rel="self"' should return your self-link.
Subscribe in two different readers (NetNewsWire and a web reader). Trigger a deploy that does not change content. Confirm no item duplicates appear in either reader.
Inspect a few items: each <guid> should be stable across builds for the same post.

Sources & further reading

RSS 2.0 Specification — RSS Advisory Board
RSS Best Practices Profile — RSS Advisory Board
RFC 4287 — The Atom Syndication Format — IETF
RDF Site Summary 1.0 Modules: Syndication — RSS-DEV Working Group
RFC 5005 — Feed Paging and Archiving — IETF
W3C Feed Validation Service — W3C