RSS Feed Errors are one of the issues you'd have to overcome while running a WordPress-powered website.
These kinds of errors hinder you from adequately utilizing your WordPress RSS Feed.
Usually, this errors are caused by poor formatting. WordPress outputs RSS feeds in XML which is a strict markup language. A missing line break or an extra tab can break your RSS feed.
The RSS error message will look something like this:
XML Parsing Error: XML or text declaration not at start of entity
Line Number 2, Column 1:
Depending on the browser that we use, our RSS feed error message may vary.
We can also see this error message when visiting our feed in a browser.
Warning: Cannot modify header information – headers already sent by (output started at /home/username/example.com/wp-content/themes/twentysixteen/functions.php:433) in /home/username/example.com/wp-includes/pluggable.php on line 1228
Here, you see different methods to resolve this WordPress error.
If we recently added a code snippet to our theme or child theme's functions.php file, then we need to edit our functions file.
If there is a closing PHP tag at the end of our functions file, then we need to make sure that there is no extra space or line breaks after it.
Ideally, the closing PHP tag is not required at the end of the file.
This is why it would be best if we remove the closing php tag altogether.
This should fix the problem in most cases.
If we are using a WordPress plugin that modifies our website’s RSS feed or creates a new one, then we need to disable that plugin.
If we are unsure, then we can temporarily disable all WordPress plugins.
Next, check our RSS feed for the error. If the error disappears, then this means one of the plugins installed on our website was the culprit.
We can now reactivate our installed plugins one by one and check our RSS feed after activating each plugin. This way we will be able to find out exactly which plugin is causing the issue.
Once we have located the plugin, we can contact the plugin’s support for an update or find an alternative plugin that does the same thing.
Occasionally, a poorly coded WordPress theme function can also affect our WordPress RSS feed. To see if the problem is caused by our WordPress theme, we need to temporarily switch to a default WordPress theme.
Simply go to Appearance » Themes page and if we already have a default theme installed, then activate it.
Default themes include Twenty Nineteen, Twenty Seventeen, Twenty Sixteen, and so on. If we do not have one installed on our website, then we can click on the Add New button to install and activate it.
After switching to the default theme, check our WordPress feed for error.
We can visit our feed in a browser window or test it with a feed validator tool.
If the error disappears, then this means our WordPress theme was causing the issue.
We can contact the theme author for support or find a suitable new theme for our website.