The Show IDs plugin displays the ID of all posts, categories, pages, taxonomies, users, tags, and more.

Adds menus to the WordPress Toolbar to display blog, page, post and attachment IDs along with other related information.

Get list of post IDs by taxonomy, post-type, template. Add ID column in posts, media, taxonomies, users screens with option to copy selected IDs.

This plugin displays the IDs in the admin section.

What this plugin does is to shows the IDs on admin section.