Dipak Kumar Pusti

After release of WordPress 2.5, the IDs on all admin pages have been removed as it was, probably due to the fact that the common user don’t need them. However, for advanced WordPress users / developers those IDs were quite interesting for some plugins or template tags.
What this plugin does is to display IDs on admin pages, showing the IDs, as it was in versions prior to 2.5

Display IDs

What this plugin does is to display IDs on admin pages, as it was in versions prior to 2.5

水野史土

This plugin shows post/page/category/tag/comment/media/user IDs on admin’s edit post/page/category/tag/comment/media/user pages. You can see the ID when you visit an edit post/page/category/tag/comment/media/user page. 
Since this plugin hooks on ‘edit’ link, only users with priviledges can see IDs. For example, a user of author role can see post IDs, while a user of subscriber role cannot.
You can find a brief description in Japanese on a book <a href="https://php4wordpress.calculator.jp/" rel="nofollow ugc">Introduction to PHP for WordPress Users.</a> (written in Japanese.)

ShowID for Post/Page/Category/Tag/Comment

This plugin shows post/page/category/tag/comment/media/user IDs on admin's edit post/page/category/tag/comment/media/user pages.

Display IDs vs ShowID for Post/Page/Category/Tag/Comment