KLicheR

Create a unique ID to easily identify repeater field’s rows. The field is fulfill on the first “save” of the post.
Compatibility
This ACF field type is compatible with:
<ul>
<li>ACF 5</li>
</ul>

Advanced Custom Fields: Unique ID Field

Create a unique ID to easily identify repeater field's rows.

Fineswap

<a href="//wordpress.org/plugins/ninja-forms/" rel="nofollow ugc">Ninja Forms</a> is a great WordPress plugin and this plugin makes it even greater!
If you’re using Ninja Forms for gathering data and one or more of textbox fields 
must be unique, this plugin is for you. The plugin is pretty straightforward to 
install, and has few settings only (language settings, basically).
Once installed, it will validate every submission to make sure the values for 
one or more fields are unique.
Brought to you by <a href="http://fineswap.com/?utm_source=wordpress&utm_medium=plugin&utm_term=readme-desc&utm_campaign=ninja-forms-unique-textbox" title="A blog and a mobile app advocating sustainability and green living" rel="nofollow ugc">Fineswap</a> Team.

Ninja Forms Unique Textbox

Extend Ninja Forms' functionality by allowing textbox field to have unique values.

Advanced Custom Fields: Unique ID Field vs Ninja Forms Unique Textbox