Whenever we or someone else shared a web page on Facebook, Facebook extract the meta data of URL and show it with shared URL. Not only it shows on the post, it also cache this meta data and use it when the link is shared again on Facebook.
If you have made any changes to the meta data of a URL, you will not be able to see the changes on Facebook. I am not sure when the cache expires on Facebook, but it saves it for long time. If you are in bad need to make changes in the meta data to show on Facebook, the moment can be frustrating for you. Very few people know why the changes not reflect on Facebook.
To make instant changes in the meta data on Facebook, we need to flush the cache manually. Facebook has given an option for this. You just need to use following URL.
Here replace [YOUR_PAGE_URL] with the URL of your website’s URL.
After visiting the above URL with your web page URL, you will try sharing the web page again on Facebook. This time, Facebook will extract meta data again and changes will be there.
Read: Compress CSS with PHP