Atom 1.0

<summary>

A short description of an entry — optional most of the time, and required exactly when the content is remote or not text.

<summary> is a text construct with the same type attribute as <title>. Most of the time it is optional and used as a teaser alongside a full <content>.

It becomes required in two cases: when <content> carries a src attribute, and when its type is neither text, html nor xhtml. Both mean the reader cannot show anything useful without fetching or decoding something, and the summary is what it shows instead.

Format: Atom 1.0
Namespace: Atom Syndication Format 1.0
Parent: <entry>
How many: At most one per <entry>.

What it contains

Nothing — this element holds a value rather than other elements. Its content is text, and the constraints below are what that text has to be.

Attributes

typeoptionaltext, html or xhtml. Defaults to text.

Cardinality and constraints

At most one per <entry>.

Required when <content> has a src attribute, or a type outside text, html and xhtml.
type is text (default), html or xhtml, as for <title>.
Otherwise optional, and conventionally a teaser rather than the whole body.

What our validator does

Not checked. The conditional requirement depends on the sibling <content>, and our feed checks do not model it.

We do not catch this one

The content is a remote PDF, so a <summary> is required and there is none — a reader has nothing at all to display. Our feed checks do not implement the rule, so both documents pass.

Broken and fixed

Both documents below are well-formed XML — that is the point of this corpus — and both are run through the validator on every test run. The verdicts here are what it returned, not what we expect it to.

broken

<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
  <id>urn:uuid:60a76c80-d399-11d9-b93c-0003939e0af6</id>
  <title>Example</title>
  <updated>2026-08-10T09:00:00Z</updated>
  <author><name>Ada Lovelace</name></author>
  <entry>
    <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
    <title>Hen lays egg</title>
    <updated>2026-08-10T09:00:00Z</updated>
    <content type="application/pdf" src="https://example.com/egg.pdf"/>
  </entry>
</feed>

No issue reported. This defect passes our checks.

fixed

<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
  <id>urn:uuid:60a76c80-d399-11d9-b93c-0003939e0af6</id>
  <title>Example</title>
  <updated>2026-08-10T09:00:00Z</updated>
  <author><name>Ada Lovelace</name></author>
  <entry>
    <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
    <title>Hen lays egg</title>
    <updated>2026-08-10T09:00:00Z</updated>
    <summary>A hen laid an egg. The full report is a PDF.</summary>
    <content type="application/pdf" src="https://example.com/egg.pdf"/>
  </entry>
</feed>

No errors. Warnings may remain — a conforming feed can still be missing a self link — but nothing here is wrong.

Where it reaches

Related elements

All 34 elements

Get started

Bring order to the XML your team can't afford to ignore.

Create a free account and get a private workspace to search, validate, diff, and monitor your XML feeds, sitemaps, schemas, and vendor integrations.

Get started free Sign in