Tauno Hanni

This plugin is a developer’s toolkit for collecting form data from your WordPress site. It provides the necessary hooks and utilities for you to manage how data is stored and displayed later.
The best way to get started is to look at example-functions.php and example.php in <code>/plugins/form-data-collector/example</code> folder.
You can see a list of utilities and hooks <a href="https://github.com/taunoha/form-data-collector/wiki/" rel="nofollow ugc">here</a>.
Not compatible with 1.x.x versions 🙁

Form Data Collector

This plugin will help you to collect and store form data.

AMP-MODE

Scott DeLuzio

If you sell a product through your WooCommerce store that requires you to collect some additional information from your customers before they complete their purchase, this plugin is exactly what you need.
Pro Version Now Available 
<a href="https://conditionalcheckoutfields.com/downloads/conditional-woo-checkout-field-pro/" rel="nofollow ugc">Update to Pro</a> to get even more features.
<ul>
<li>Display an unlimited number of custom conditional fields at checkout (free version only allows one).</li>
<li>Display each conditional field on an unlimited number of products, product variations, or categories of products (free version only allows the field to display for one product).</li>
<li>Increased variety of available input fields including: Text box, multi-line text area, drop-down/select menu, country list, state list, check boxes, password, radio buttons, and date picker.</li>
<li>Bonus: Easily edit any of the default WooCommerce checkout fields without having to edit any code.</li>
</ul>
Get the pro version by <a href="https://conditionalcheckoutfields.com/downloads/conditional-woo-checkout-field-pro/" rel="nofollow ugc">clicking here</a>.
This plugin lets you configure an additional field to be displayed at checkout for your customer to fill out provided a certain product is in the customer’s cart.
The plugin allows you to customize this additional field’s
<ul>
<li>Title</li>
<li>Input type (text box, text area, or select/drop down menu)</li>
<li>Label</li>
<li>Placeholder text</li>
<li>CSS Class</li>
<li>Whether or not the field is required (and the error message to display if it is required but not filled out)</li>
<li>Whether or not to add the customer’s input to the order email or invoice</li>
</ul>
This plugin requires your site to have WooCommerce installed in order to work. It is not compatible with other e-commerce plugins.

Conditional WooCommerce Checkout Field

Display a custom field at checkout in your WooCommerce store if a certain product is in the customer's cart.

Form Data Collector vs Conditional WooCommerce Checkout Field