rsspodcast

What's the difference between <pubDate> and <lastBuildDate> for a podcast rss feed?

Can anyone familiar with creating podcast rss feeds please explain this one to me...

Q: What's the difference between <pubDate> and <lastBuildDate> for a podcast rss feed?

For context, <pubDate> and <lastBuildDate> are specific fields within an rss feed.

There are plenty of well-meaning descriptions available to research, e.g.

Unfortunately, it is still confusing me.

Initially, I have tried to look at it from the point of view of a physical publication, e.g. a book.

This example makes perfect sense to me. It works well for something with a physical copy.

However, how does that work for an electronic resource like a podcast?

With a podcast, when you create a new episode, or update the description, i.e. lastBuildDate, you also update the feed, i.e. pubDate. Usually at the same time.

Therefore, there appears to be no difference between <pubDate> and <lastBuildDate> for a podcast?🤷‍♂️

Is there something I am missing / not understanding?

Thanks in advance for your thoughts and ideas.

Solution

  • Initially, I have tried to look at it from the point of view of a physical publication, e.g. a book.

    This is an excellent way to think about it. And you're correct. I don't think you should be confused by anything.

    To further clarify:
    1. The lastBuildDate can also be modified by the content generator (the code that creates the feed markup) if it internally modifies any metadata known only to itself.
    2. As both fields are optional, you should not rely directly on them for detecting new content if that's your purpose. HTTP Cache related headers are better suited for this.
    3. Even for non-podcast feeds, pubDate when available should be used IMO. Additionally also check for pubdate. Some feeds publish the lower-cased variant of it as well.