The Awesome List of RSS Feed Validators
Use this list of free RSS validators to keep your feed code clean, and your RSS feed available to your audience.
W3C: W3C is for syndicated feeds. It works with RSS 0.90, 0.91, 0.92, 0.93, 0.94, 1.0, and 2.0. Enter the address of your feed and click “validate.” Errors will be highlighted, with messages for each problem. Not sure what the message means? There’s a “help” link with more details.
RSS Validator: Enter the URL of an RSS feed for quick validation.
Podbase: For podcast feeds. Podbase will check your URL, make sure your XML is well formed, and whether it is iTunes-compatible. It will also check for things like your cover art being in iTunes compliance, correct category, correct summary, and more.
Feed Validator: Feed Validator is for Atom, RSS, and KML feeds. Like W3C, it also gives you highlighted errors with messages and information for each problem found.