Den OPML

Den uses custom OPML attributes to preserve channel settings when exporting and importing files.

The attributes belong to the XML namespace this page is published at:

<opml version="1.0" xmlns:den="https://den.io/xml/opml">

The namespace defines attributes only — no elements. Attributes appear on standard OPML <outline> elements alongside common attributes such as text, title, type, and xmlUrl. Every attribute is optional, and applications that do not recognize the namespace can safely ignore it: a Den export without the den: attributes is a plain OPML subscription list.

Folder attributes

Folder outlines are outlines without an xmlUrl attribute.

Attribute	Type	Description
`den:icon`	string	SF Symbols name for the folder icon, e.g. `globe.americas`. Defaults to `folder`.

Channel attributes

Channel outlines are outlines with an xmlUrl attribute.

Attribute	Type	Description
`den:disableBlocklists`	boolean	Disable content blocklists in the channel’s viewer. Defaults to `false`.
`den:disableJavaScript`	boolean	Disable JavaScript in the channel’s viewer. Defaults to `false`.
`den:generatePreviewSummaries`	boolean	Generate machine summaries for article previews. Defaults to `false`.
`den:viewerMode`	`web`, `comments`, `content`, or `reader`	Preferred article presentation. When absent, Den chooses automatically.
`den:fetchLimit`	integer, 1–1000	Maximum number of articles kept per fetch. Defaults to 10.
`den:retentionPeriod`	integer, 1–3650	Article retention period in days. Defaults to 30.
`den:ttl`	non-negative integer	Minimum time between feed refreshes, in minutes.
`den:translationLanguage`	BCP 47 language code	Target language for automatic article translation, e.g. `en`. Absent when translation is off.
`den:languageOverride`	BCP 47 language code	Manual source-language override for feeds that misreport their language, e.g. `de`.

Boolean values are the lowercase strings true and false; the numeric forms 1 and 0 are not recognized. Integer values outside their documented range are clamped on import rather than rejected.

Example

<?xml version="1.0" encoding="utf-8"?>
<opml version="1.0" xmlns:den="https://den.io/xml/opml">
<head>
<title>Den Library</title>
<dateCreated>Sun, 30 Aug 2026 12:00:00 GMT</dateCreated>
</head>
<body>
<outline text="News" title="News" den:icon="globe.americas">
<outline text="Example Feed" title="Example Feed" type="rss"
    xmlUrl="https://example.com/feed.xml"
    den:disableBlocklists="false" den:disableJavaScript="false"
    den:generatePreviewSummaries="true" den:viewerMode="reader"
    den:fetchLimit="25" den:retentionPeriod="90"/>
</outline>
</body>
</opml>

Import behavior

Den’s importer resolves namespaces when reading OPML files:

Attributes qualified with any prefix bound to https://den.io/xml/opml are recognized, regardless of the prefix used.
As a compatibility fallback, attributes using a bare den: prefix are also recognized when the prefix is not declared.
Attributes whose den: prefix is explicitly bound to a different namespace are ignored.

Schema

An XML Schema describing the attributes is available at https://den.io/xml/opml/den-opml.xsd. Because OPML itself has no official schema, the schema declares the Den attributes only; it documents recommended value ranges and is suitable for validating the attributes as a foreign vocabulary rather than for validating complete OPML documents.