All you do is enter an RSS or Atom feed URL (or simply a website URL and the feed URL will be auto-detected) and the analyzer, using SimplePie, will tell you everything you ever wanted to know about that feed but were afraid to ask. It answers questions like:

• What is the effective feed URL?
• What is the feed description?
• Is the feed copyrighted?
• Does the feed have a channel image?
• Is the feed localized with a latitude/longitude data?
• Do feed items have publication dates? (some don’t which can cause problems in multifeeds)
• Does the feed’s corresponding website have a favIcon?
• What is the feed’s title?
• What is the feed’s source website link?
• What type of feed is this? RSS? Atom? RDF?
• What language is the feed in?
• How is the feed encoded? UTF-8? ISO-8859-1?
• Who is the author of the feed?
• How many items are there in the feed?
• How often are posts made?
• What is the oldest feed item? (tells you how long your cache duration should be)
• Are posts sorted by date? If so, are they sorted (reverse) chronologically?

In addition, the analyzer gives you:

• A summary of all items in the feed.
• A detailed list of all the items in the feed.
• A list of all the sub-elements in an item element along with the required SimplePie code to extract those elements.
• A dump of the raw HTTP data for the feed so you can visually check the feed’s HTTP headers and body for errors.
• A demo of the feed.

Bonus:

• Allows easy integration with Firefox’s feed subscription feature.
• Validate the feed at FeedValidator.org.