Alex Prokopenko / JustCoded

Just Custom Fields adds ability to extend your Posts, Pages (and other custom post types) and Taxonomies with additional fields. After installation, you will see a simple settings page, which is self-explanatory to use. 
We use the standard WordPress PostMeta API and TaxonomyMeta API to save fields data, so you can use standard WordPress functions in your themes/plugins to get data.
IMPORTANT We do not recommend update plugins on your existing sites from version 2.* to version 3.0+. 
JCF v3.0+ is not compatible with versions 2.*, so some field settings can be lost (and as a result – wrong values on post edit pages).
Plugin supports such field types:
<ul>
<li>Input text</li>
<li>Select Box</li>
<li>Multiple Select Box</li>
<li>Checkbox (single and multiple)</li>
<li>Textarea (you can use WordPress editor too)</li>
<li>Datepicker</li>
<li>Simple Media (files and images upload)</li>
<li>Table</li>
<li>Fields Collection (repeatable fields groups)</li>
<li>Related Content (to set a relation to another Post/Page or Custom Post Type)</li>
</ul>
You can read full documentation on our site: http://justcustomfields.com.
For quick demo you can watch our presentation video: 
https://www.youtube.com/watch?v=7KJeH2d_v48
Starting from v2.0 we have different options to save plugin configuration:
<ul>
<li>Ability to set Fields Settings global if you have MultiSite. So you can set them once, without copying all settings to every new site.</li>
<li>Ability to save Fields Settings to a file system (inside theme or wp-content folder). We expect this option will be popular among the developers. It will be much easier to move your fields’ settings between site versions (dev/production).</li>
</ul>
Starting from v2.2:
<ul>
<li>Simple Media field is now a single file only (before it was multiple). It uses new media upload box from WordPress and saves post thumbnail ID (before it was just a file url). So now you can use the get_the_post_thumbnail() function to work with attachments.</li>
<li>All fields now have “Shortcodes” and hints how to use them inside the templates for non-professional developers.</li>
</ul>
For easy migrations between different sites, we have Export/Import options.
FEEL FREE TO CONTACT ME IF YOU FIND ANY BUGS/ISSUES!
ISSUES TRACKER 
Plugin code is open source and placed in the GitHub public repository. I listed known bugs and future features there. You can post new bugs or feature requests for me there. 
https://github.com/aprokopenko/justcustomfields/issues

Just Custom Fields

Turn WordPress into more powerful CMS by adding advanced and easy to use custom fields

Themepure

The Pure Metafields Plugin is a powerful tool designed to enhance the functionality and flexibility of your WordPress website. With this plugin, you can easily create and manage custom meta boxes, adding extra fields and data to your posts, pages, and custom post types.
<h3>Key Features</h3>
✅ Custom Meta Boxes: Create unlimited custom meta boxes with ease. Define the title, placement, and priority of each meta box to suit your needs.
✅ Flexible Field Types: The plugin offers a wide range of field types to choose from, including text, textarea, select, checkbox, radio buttons, date picker, and more. Customize the field options and validation rules effortlessly.
✅ Repeatable Fields: Enable the ability to repeat fields, allowing users to add multiple instances of the same field dynamically. Perfect for scenarios where you need to capture multiple sets of data.
✅ Conditional Logic: Set up conditional logic to show or hide fields based on the value of other fields. This feature adds versatility and improves the user experience of your forms.
✅ Built-in Validation: Ensure data accuracy by implementing validation rules for your fields. You can define required fields, validate input formats, and customize error messages effortlessly.
✅ Save and Retrieve Meta Data: The plugin provides simple functions to save and retrieve meta data, allowing you to access and utilize the stored information in your themes or plugins.
✅ Integration with WordPress API: Seamlessly integrate with the WordPress API and extend its functionalities. Hook into actions and filters to manipulate meta data and create dynamic interactions.
<a href="https://themepure.net/plugins/puremetafields/" rel="nofollow ugc">Live Docs</a>

Pure Metafields

Very light weight playable plugin

Pure Metafields is very light weight plugin tused to create custom metabox for any post type like page, post and your custom post type support it.

Just Custom Fields vs Pure Metafields