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Flushing a cache is a fancy word for deleting the cache. Deleting a cache simply means that it will be rebuilt the next time a person requests the relevant section of the website. It's something you might want to do if you have recently updated content and you want to make sure that the website is showing the very latest information.
Content Cache Detail
Drilling down on a content cache block or category shows all of the specific caches in that block. From here you can individually delete cache items, or drill down further to see the actual fragment of HTML in the cache.
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