Paste your feed URL into the W3C Feed Validation Service and click Check. The validator fetches the feed, compares its XML against the RSS or Atom specification, and reports any errors with their line numbers. If the feed conforms, the result says so. If it doesn't, you get the specific problems and where they occur.
Don't have the feed URL?
A validator needs the URL of the feed itself, not the website's home page. The two are rarely the same.
If you're looking at a site and want to find its feed, How to Find an RSS Feed URL covers the common patterns for WordPress, YouTube, Reddit, and other platforms. Once you have a URL that points to XML, you can validate it.
What an RSS Validator Checks
An RSS feed is an XML document with a defined structure. A validator reads that document and compares it against the rules of the specification it claims to follow: RSS 2.0, RSS 1.0, or Atom 1.0.
The check covers required elements like <title> and <link>, date formats (RFC 822 for RSS 2.0), URL formatting, character encoding, and namespace declarations. Some validators also flag best-practice recommendations that aren't strictly required by the spec.
A validator reads the feed and reports on it. It does not modify or repair the source. If the feed has problems, you or whoever controls the feed need to fix them in the CMS, the feed plugin, or the XML template that generates it.
Free RSS Feed Validators
Three tools handle the common cases. All are free, and none require an account.
| Validator | Formats | Best for |
|---|---|---|
| W3C Feed Validation Service | RSS, Atom | The standard reference for RSS and Atom syntax. Separates errors from recommendations. Accepts URL input and raw XML paste. |
| RSS Advisory Board Validator | RSS 2.0, RSS 1.0, Atom | Run by the RSS Advisory Board, which maintains the RSS 2.0 specification. Pairs well with their Best Practices Profile. |
| rssvalidator.app | RSS 2.0, RSS 1.0, Atom, JSON Feed, podcast RSS | Adds a content preview and podcast tag checking (iTunes/Apple Podcasts) alongside validation. |
If a result from one validator surprises you, running the same feed through a second validator is a fair way to check whether the issue is a real spec violation or a strictness difference between tools.
How to Read Validation Results
The W3C validator returns one of three outcomes:
- Valid, no messages. The feed conforms to the specification. Nothing to address.
- Valid, with recommendations. The feed conforms, but the validator suggests an improvement. Recommendations are best-practice notes, not failures.
- Not valid. The feed has structural or syntax errors. Each error includes a line number and a description of what the specification requires at that point.
When we last checked (August 2026), this site's own feed (wprssaggregator.com/feed/) returned a valid result with one recommendation: replace the SVG channel image with one of the image formats the validator expects.
The same feed, loaded into Aggregator on a local WordPress install, showed 24 available items and imported successfully. Valid feed, one recommendation, no import problem.
A feed that returns "Valid" with a few recommendations still validates. You do not need to resolve every recommendation before using the feed. Errors are different: they mean the XML does not conform, and some consuming applications may refuse to parse it.
What "Valid" Proves
A valid result establishes that the feed's XML conforms to the specification. Feed readers, podcast directories, email newsletter tools, and WordPress importers each have their own requirements beyond XML syntax, so a feed that passes a validator can still fail to import for other reasons.
Some of those reasons are invisible to a syntax validator because they have nothing to do with the XML itself:
- The server sends the wrong
Content-Typeheader, so a consuming application refuses to treat the response as a feed even though the body is well-formed XML. - The host blocks automated requests, or the feed requires authentication.
- Items lack a unique identifier, so a consumer either drops duplicates or imports nothing new.
- An application applies stricter rules than the specification for its own reasons.
Aggregator's own changelog shows the gap in practice. The 5.2.1 release added handling for feeds that had valid RSS content but arrived with an incorrect Content-Type header, and a fallback for items without a <guid> element.
A syntax validator would call those feeds clean because it checks the XML, not the HTTP headers or optional elements like GUIDs. An importer that checks headers before parsing, or relies on GUIDs for deduplication, could still reject or mishandle them.
A minor warning may not stop the feed from working in the application you need it for. Validation checks the structure; testing the feed in that application shows whether it can actually use it.
Common Feed Errors
Most validation failures fall into a few patterns:
- Malformed XML. Unclosed tags, unescaped ampersands, or invalid characters. Often caused by content that includes raw HTML without CDATA sections.
- Missing required elements. RSS 2.0 requires
<title>,<link>, and<description>at the channel level. Each item needs at least a<title>or<description>. - Invalid date format. RSS 2.0 expects RFC 822 dates (like
Thu, 01 Jan 2026 12:00:00 GMT). ISO 8601 dates or freeform strings fail validation. - Broken URLs. Spaces, unencoded special characters, or relative paths in
<link>or<enclosure>elements. - Encoding mismatch. The XML declaration specifies one encoding but the content uses another. Common when a feed generator outputs UTF-8 content with a Latin-1 declaration.
If you publish the feed, these are fixable in your CMS settings, your feed plugin, or your XML template. If the feed belongs to someone else, the next section covers your options.
When You Don't Control the Feed
If you're consuming a feed from another site and the validator reports errors, you can't edit the XML. Your practical options:
- Test it in the application you plan to use. Many feed consumers are more forgiving than a strict validator. If the feed works despite the warnings, the warnings don't block you.
- Contact the publisher with the specific error message, especially for errors that clearly break the specification.
- Look for another feed from the same source. Many sites offer category feeds, tag feeds, or Atom alongside their main RSS feed. One of them may validate cleanly when another does not.
If the feed doesn't work and you can't reach the publisher, a different feed from the same site or a different source entirely may be the simpler path.
Testing a Feed in WordPress
If the feed is headed for a WordPress site, the practical test is adding it as a source in Aggregator.
Go to Aggregator > Sources and add a new source. Paste the feed URL into the Source Link field. Aggregator fetches the feed and shows a preview of the available items before you save.
If the preview returns items, the feed is readable by the plugin regardless of what a validator reported. If it returns nothing, the problem could be the URL, the feed itself, or a server blocking automated requests.
To complete the test, save the source and run an import. Aggregator confirms when the feed items have been imported successfully.
You can also type a website URL into the same field, and Aggregator will try to discover available feeds on that site.
This does not replace validation. It shows whether Aggregator can read the feed in its real environment, including the headers and server behavior that a syntax validator does not test.
Checking Content Before You Import
Before importing, you may also want to inspect what the feed actually contains. Feed Finder shows item availability, freshness, full text, images, authors, dates, and duplicate risk. It does not check XML syntax or replace a validator.
Turn a valid feed into a working WordPress source
Install Aggregator, paste in the feed URL, and preview the available items before you save the source.
Get AggregatorRSS Validation FAQ
How do I check an RSS feed?
Paste the feed URL into the W3C Feed Validation Service and click Check. The validator fetches the feed, checks its XML against the RSS or Atom specification, and reports any errors with line numbers and descriptions.
Why isn't my RSS feed working?
A feed can stop working for reasons beyond XML validity: the server may be down, the URL may have changed, the feed may require authentication, or the consuming application may not support the feed's content type or encoding. Run the URL through a validator to rule out structural problems first, then test it directly in the application that isn't reading it.
How do I find my RSS feed URL?
Most WordPress sites publish a feed at /feed/. For other platforms, check the page source for a <link> element with type="application/rss+xml", or see How to Find an RSS Feed URL for platform-specific patterns.
What is the difference between errors and warnings?
Errors mean the feed violates the specification. Warnings or recommendations mean the feed passes but could improve on a specific detail. A feed with recommendations but no errors still validates. Errors should be resolved before relying on the feed. Recommendations are worth reviewing but do not prevent the feed from being used.
