yehudaT

Adds a button to the WC edit/new product page that enables generating a SKU (catalog number) in a pre-defined format and length. It is aimed for Woocommerce shop admins who manage a shop with no pre-defined catalog numbers for products.
When adding or editing a product it is common that you do not have a pre-set catalog number for the product. 
This plugin enables you to generate a SKU (catalog number) for the product, with specified format and length. 
It also checks that the suggested SKU does not exist in the database for any other product.
At the same time you can use it to check a SKU number you enter.
Starting on V 1.0.1 you can choose to add automatic SKU for every new product or existing product without a SKU (no need to click a button or select).
You also can select not to generate a random SKU, but write it yourself, and the plugin will check asynchronously if the SKU already exist in the database.
<blockquote>
Tested up to Woocommerce Version 6.0.0
Important! version 1.0.2 and up works with Woocommerce 2.6.0 and up. If you have earlier version of WC please use this plugin version 1.0.1
</blockquote>
<h4>Features</h4>
<ol>
<li>None intrusive. The plugin adds the SKU to the SKU field in the product edit page but it saved only by you. </li>
<li>Option to add auto prefix to the generated SKU.</li>
<li>Option to auto fill SKU for new product.</li>
<li>3 flexible SKU formats – between min-max numbers, string (you can select any alpha numeric combination), Incremental (auto increment next SKU)</li>
</ol>

SKU generator for Woocommerce by ATR

Generates custom SKUs for WooCommerce products automatically or on-demand, with flexible formatting options and duplicate checking.

hpgong

The purpose of Simple SKU Generator plugin is to create SKU for the products.
<h3>Instructions</h3>
Click here <a href="https://github.com/hp-gong/hp-sku-generator/raw/master/sku-overview.pdf" rel="nofollow ugc">sku-overview.pdf</a> to download the instructions
Read the sku-overview.pdf for more details how the plugin works
These are the 4 current browsers that currently support/display this plugin correctly:
<ol>
<li>FireFox (Current Version: 84.0.2 and up)</li>
<li>Chrome (Current Version: 87.0.4 and up)</li>
<li>Opera (Current Version: 73.0.3 and up)</li>
<li>Microsoft Edge (Current Version: 87.0.6 and up)</li>
</ol>

Simple SKU Generator

doesn't work for variable products, a bit convoluted to use.

doesn't work for variable products

The purpose of Simple SKU Generator plugin is to create SKU for the products.

SKU generator for Woocommerce by ATR vs Simple SKU Generator