The following required properties are missing: fb:app_id

When you test your page using Facebook Sharing Debugger and get the warning "The following required properties are missing: fb:app_id",

you need to add fb:app_id meta tag to the <head> tag of your page:

<meta property="fb:app_id" content="ХХХХХХХХХХХХХХХ" />

Replace ХХХХХХХХХХХХХХХ with your Facebook App ID.

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If you use Magento 2, you can easily do this without any technical knowledge following the steps below:

1. Go to Admin Panel > Content > Design > Configuration and choose the Store View you want the required properties to be added to by pressing the Edit button.

2. Once you're there find the HTML Head section and add this code:

<meta property="fb:app_id" content="ХХХХХХХХХХХХХХХ" />

to the Scripts and Style Sheets field, example:

3. After you've finished don't forget to press the Save Configuration button.

4. Flush the cache and you are free to test it. However, it may take some time for Facebook to update its cache.