You can use the debug snippet to debug snippet filters. Snippet debugging works by logging messages to the browser's console about the snippet and its current status.
Consider the following example:
example.com#$#debug; log Hello
In this filter, the debug snippet after the domain sets a debugging flag that remains true until the end of the snippets chain. Because you can chain multiple snippets into a single filter, debug affects all snippets in the filter.
For more information, view the debug snippet documentation.