What are the valid HTML tags in RSS Feeds?

Question

I've looked around, and it doesn't seem like there's any standard of what HTML tags are 'allowed' in RSS - you could put anything in. But the readers I tested only allow certain things.

In my initial testing, it seems like simple styling tags like <b> are fine. So is inline styles like <span style="color:red"> <img>'s seems to work.
But <iframe>'s are ignored, as are <script> blocks.
Onclick attributes don't work.
<style> blocks work in some readers but not others

Is there a general consensus, standard, or comparability site listing what is and isn't supported in what readers?
I want to know what the subset of HTML tags I can use in feeds is.

Do you just put in the tags as they are, or is there some special markup for them? Cuz I figured HTML tags would be misinterpreted by XML readers as separate items. — Kelvin Shadewing
– Kelvin Shadewing, Commented Mar 3, 2016 at 21:44
@artlung what is wrong with the existing answers here? The answer is, it depends on the client. Given that RSS is (to be charitable) far less prominent than it was when this question was asked, I can't imagine what you expect to have changed in the intervening 15 years. — miken32
– miken32, Commented 19 hours ago
@miken32 feel free to leave that as an answer if you feel that is an adequate answer. — artlung
– artlung, Commented 16 hours ago

Mister Jojo · Accepted Answer · 2025-11-21 03:48:22Z

11

<title>How to parse full html content in xml feeds</title>
<description><![CDATA[<html><body>Any code html is valid here like &npsb; 
 and what ever you want to transfer</body></html>]]></description>
<guid>http://example.com/your-news-id</guid>

edited yesterday

Mister Jojo

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answered Dec 19, 2012 at 9:15

ashraf mohammed

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1 Comment

MrU Over a year ago

Whilst all HTML tags are supported by the spec, the feed readers only support a limited range of tags.

Matchu · Accepted Answer · 2009-07-16 21:13:10Z

2

I don't think there's a standard here - it's all about what the RSS reader itself is willing to implement. So my guess would be that, for example, Google Reader would wash out tags and the like and dangerous HTML and CSS attributes, and then allow whatever other sort of non-blacklisted tag you would dare to include.

So, yeah. There's no specification, and therefore likely no standard - just the same general XSS prevention techniques we see across the whole interwebs. Your only option is to try out various tags that you think may be contentious (though really I'd expect almost anything but CSS styling would be permitted) in different RSS readers to see what happens, or simply to have your content ready to fall back to a more basic format if the desired HTML/CSS is not permitted.

What in particular are you trying to do? You may be able to get better answers if you can specify - or is this just a question of curiosity?

answered Jul 16, 2009 at 21:13

Matchu

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2 Comments

Tom Ritter Over a year ago

Mostly curiosity. I'd love to let users do things like vote up and down articles using javascript and ajax from within a RSS Reader, but I guess the best I'll be able to do is external links with unique tokens.

Matchu Over a year ago

Mhm. If my RSS Reader allowed Javascript, well, I'd just be mad. It's tough being both a developer and a user xD

Stijn Sanders · Accepted Answer · 2009-07-16 21:22:41Z

1

I think the 'right' thing to do is either include an xhtml namespace (xmlns:html="http://www.w3.org/1999/xhtml") or put the HTML data in a CDATA section.

answered Jul 16, 2009 at 21:22

Stijn Sanders

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Comments

buzz8year · Accepted Answer · 2025-11-22 02:46:11Z

1

Supported meta tags (many can have attributes if proper):

<!-- RSS comment -->
<copyright>
<channel>
<title>
<description>
<category>
<image>
<link>
<comments>
<language>
<item>
<guid>
<source>
<author>
<enclosure>
<pubDate>
<lastBuildDate>
<managingEditor>
<webMaster>
<generator>
<docs>
<cloud>
<ttl>
<rating>
<textInput>
<name>
<skipHours>
<skipDays>

Supported body tags:

<p>, <span>, <strong>, <b>, <i>, <em>, <br>

Supported body tags with attributes:

<a href="URL">
<img src="URL" alt="description">

Supported body tags by some readers (you will need to test it):

<picture>, <figure>, <div>, <h1>, <h2>, <h3>, <h4>, <h5>, <h6>, <span style="color:red">

Not supported:

<iframe>, <script>, <style>

IMPORTANT:

Use plain text within all tags to avoid issues
All elements must have a closing tag
Elements are case sensitive
Elements must be properly nested
Attribute values must always be quoted
There is no official standard for RSS
It is not possible to cover whole topic here
Use resources to keep valid and up-to-date

https://www.w3schools.com/xml/xml_rss.asp

https://www.rssboard.org/rss-specification

https://www.rssboard.org/rss-validator/

SANITIZING / TESTING: it does not seem there are any public test suites. Yet, it's worth seeing following:

https://digialert.com/index.php/resources/blog/blog/vulnerability-assessment-and-pentesting/rss-feed-injection

https://github.com/bigapplemonkey/Feed-Reader-Testing (jasmine-based test suite for a web-based application that reads RSS feeds; seems abandoned, but can be a ramp to start)

https://github.com/FreshRSS/FreshRSS/issues/3497 (thread on FreshRSS feed filtering functionality)

edited 9 hours ago

answered 19 hours ago

buzz8year

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5 Comments

miken32 19 hours ago

[citation needed]

artlung 17 hours ago

Thanks so much for attempting an answer! Lots of good stuff on this. I suggest looking at some open source RSS Readers to quantify what they do to sanitize HTML. I know I've seen <picture> and <figure> elements come through with their associated captions correctly in a few readers. I wonder if there's a test suite to check for the sanitization process.

buzz8year 15 hours ago

Always welcome. As to testing suites - unfortunately, not aware of. Yet, see the post update, maybe it will help you somehow. And as to <picture>, <figure>, - yeah surely some readers can easily be set up to support non-standard tags.

artlung 10 hours ago

developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/… and developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/… are both standard parts of the web platform, both well supported across current browsers.

buzz8year 9 hours ago

yeah sure, yet i meant those are non-standard for rss readers, will include them to partially supported

Eli · Accepted Answer · 2009-07-16 21:15:20Z

0

I don't think there's any "official" answer. It might depend on what level of compatibility you're aiming for.

I'd keep it to the basic text formatting tags (STRONG, EM, etc) and IMG and A and that's about it.

answered Jul 16, 2009 at 21:15

Eli

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Comments

comodoro · Accepted Answer · 2012-06-10 17:30:43Z

-2

In fact, no HTML attributes are allowed in RSS feeds. Only XML tags listed in the specification posted above are allowed. Also, since it is XML, only some Unicode encodings are allowed (e.g. UTF-8). That many RSS providers do not respect the standard is another matter.

edited Jun 10, 2012 at 17:30

answered Jun 10, 2012 at 17:07

comodoro

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