Noise From My Feeds

Hello! If you are subscribed to this website's feeds, you may have noticed something odd recently. Your feed reader might have shown a bunch of old posts as if they were published today. If that happened with your feed reader, I apologise for the noise. I hope this post will give you some clarity on why this happened. The reason for this noise is a change to the way the RSS feeds are generated for this website. Each post in the feeds includes a GUID, which is used by many feed readers to decide whether a post is new or if it has been seen already. Until now, the GUID was simply the post's URL, like this:

<url>https://susam.net/product-of-additive-inverses.html</url>
<guid>https://susam.net/product-of-additive-inverses.html</guid>

However, today this has changed to a short random string, like so:

<url>https://susam.net/product-of-additive-inverses.html</url>
<guid isPermaLink="false">rxpnz</guid>

If your feed reader looks at this GUID value to decide whether a new post has been published, it will show you a whole bunch of old posts once again in your reader, as if they were new. These GUIDs won't change again in the future, so this is a one-time problem. The full URL of the post is still present in the feeds, as you can see in the example above, so your feed reader still knows where to take you if you wish to visit this website to read a post. The short random string serves as a unique identifier for each post.

This website is a passion project I work on in my spare time, and sometimes, after publishing a post, I realise the title could be sharper or the URL could be cleaner. I make the necessary changes and set up HTTP redirects on my web server, so that visitors using the old URL are still taken to the updated location of the post. Previously, however, the GUID (being the URL) changed too, which caused many feed readers to treat the updated post as a new one even when it wasn't. Switching to stable, random GUIDs prevents this problem from occurring again. The GUIDs now stay the same no matter what changes I make behind the scenes, which means no more unnecessary noise in your feed reader.

I am sorry if this caused any confusion or clutter. If your feed reader is currently flooded with old posts appearing as new, the best solution is to mark those items as read. Thank you for your patience with this issue. I hope to keep future surprises limited to content, not configuration.