Thanks so much for pointing the way to phpMyAdmin. I found editing each individual post to get rid of unwanted custom fields really time consuming, and kind of frustrating. If you miss just one instance where the value is specified, the custom field stubbornly remains.

I'm running xampp on a local machine, so I was able to nose around without worrying about breaking things. I found it really easy to clear the unwanted custom fields from my database. I've searched the forum for this information, and not found instructions for this, so for those wanting step-by-step instructions, here's how I deleted those fields using phpMyAdmin. Obviously, you should back up your database before you begin.

Go to your hosts phpMyAdmin, and select your database. In the left hand column find wp_postmeta, click to select. You'll see a table with column headers for meta values (meta_key, post_id, etc...)

Directly above this table is a "sort by key" pull down menu. Select "meta key (ascending)" or "meta key (descending)". This sorts the keys alphabetically, from the top of the list or the bottom. Where you want to start depends on the name of the meta key for the custom field you want to get rid of.

Use the arrow buttons to navigate through the pages until you find the groups of specific custom values you want to delete. You can click the big red X on the left of each value to delete each individually, or tick the check boxes to delete all or part of a page of values. At the bottom of the table there's a field for "check all" and next to that is another red X. If you check multiple boxes, use this to delete these lines all at once.

When you click to delete you'll get a "do you really want to do this" last chance to change your mind table. Remember, once you delete, it's really gone. If you are sure you have identified the correct fields, click the yes button.

And that's it. It took me all of five minutes to clear my database of a half dozen or so unwanted custom fields. Now when I write a new post, I see just the four custom fields I use on a regular basis.

OR USE THE PLUGIN https://wordpress.org/plugins/mass-custom-fields-manager/

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