RSS & Atom Feed Validator

Formats it understands

• RSS 2.0: the most common blog and podcast format. A <channel> needs <title>, <link> and <description>; each <item> needs at least a title or a description.
• Atom 1.0 (RFC 4287): stricter. The feed and every entry need <id>, <title> and <updated>, and an author must be given at feed or entry level.
• RSS 1.0 (RDF): old but still valid.
• JSON Feed 1.1: version, title and items with id and content.

The checks that save readers from trouble

• Well-formed XML. Feed readers reject a feed with a single XML error entirely. An unescaped & in a title is the usual cause; write & or wrap HTML in <![CDATA[ ... ]]>.
• Dates in the right format. RSS uses RFC 822 dates: Mon, 02 Jun 2025 08:00:00 GMT. Atom and JSON Feed use RFC 3339: 2025-06-02T08:00:00Z. Mixing them up is the most common validity error; readers then sort items wrongly or show them as new again.
• Stable, unique GUIDs and IDs. Readers use them to know which items you have already seen. If an ID changes (for example when you edit a post title and the GUID is built from it), subscribers see the item again as new. If two items share one, one disappears. A GUID that is not a URL must carry isPermaLink="false".
• Enclosures (podcast audio, attachments) need url, length in bytes, and a MIME type.
• Absolute URLs in links and in HTML inside descriptions; readers have no base URL to resolve /images/a.png against.
• A self link (<atom:link rel="self"> in RSS, <link rel="self"> in Atom) so readers know the feed's canonical address.

Worked example: a valid RSS 2.0 item

<item>
  <title>How we test widgets</title>
  <link>https://www.example.com/blog/testing</link>
  <guid isPermaLink="true">https://www.example.com/blog/testing</guid>
  <pubDate>Mon, 02 Jun 2025 08:00:00 GMT</pubDate>
  <description><![CDATA[<p>Ten years of daily use, in <b>one</b> week.</p>]]></description>
</item>

Which format should I publish?

RSS 2.0 is supported by every reader, podcast app and automation tool, so it is the safe default. Atom is better specified (dates, IDs, content types) and equally well supported by readers. Podcasts should use RSS 2.0 with the iTunes namespace that Apple Podcasts and Spotify expect. Publishing more than one format is fine as long as each is linked from your pages with <link rel="alternate" type="application/rss+xml" href="...">.

Sources

• RSS 2.0 specification (RSS Advisory Board)
• RFC 4287: The Atom Syndication Format
• JSON Feed 1.1