Sparanoid

Media Auto Hash Rename will rename any file (specific files can be ignored by file extension) during upload, with unique, low collision hashes. Hash characters and length can be configured for even lower collision rate.
More information please visit my <a href="https://sparanoid.com/work/media-auto-hash-rename/" rel="nofollow ugc">site</a>.
This plugin provides no configuration GUI to make it more easier to maintain with the future WordPress updates.
Currently there’re 3 constants you can configure in your <code>wp-config.php</code>, I recommend WP-CLI for maintaining these constants.
<ul>
<li><code>MAHR_LENGTH</code>: length of the random hashes, (default to <code>8</code>), longer can help reduce collision. Hashes at the length of 8 can be collision-free at the scale of 50,000 images).</li>
<li><code>MAHR_CHARS</code>: Characters used in hashes, default to <code>0123456789abcdefghijklmnopqrstuvwxyz_</code>, You can add more characters like uppercased alphabelts to dramatically reduce the collision without increasing the length of your filenames. But please note that this option can be dangerous if you’re not familer with general URI encoding. So if you don’t know what characters are allowed in a filename, just keep it untouched and use the default option.</li>
<li><code>MAHR_IGNORE</code>: File extensions to be ignored, default to <code>pdf, zip</code>, you can define a comma delimited list of file extensions to bypass renaming process of this plugin. All files that has the file extension you defined in the list will be ignored. Please note that:
<ul>
<li>File extensions must be defined without the leading peroid, for example: <code>'pdf, 7z, bmp'</code> works, <code>'.pdf, .7z, .bmp'</code> does not.</li>
<li>With (<code>'pdf, zip'</code>) or without (<code>'pdf,zip'</code>) space both work.</li>
<li>If you define your own ignore list, default ignore list will be discarded. For example, if you define <code>'7z'</code>, then <code>'pdf, zip'</code> will be processed during upload. You need to reapply these extensions with your own: <code>'7z, pdf, zip'</code>.</li>
<li>If you don’t need to ignore any files by its extension. define an empty array <code>[]</code> (without quotes) to this option: <code>define( 'MAR_IGNORE', [] );</code> to force process PDF and ZIP files.</li>
</ul>
</li>
</ul>

Media Auto Hash Rename

Rename media filename during upload with unique hash.

mitcho (Michael Yoshitaka Erlewine)

bmellor

WordPress’s built-in file-management is built primarily for handling “media”. But sometimes there’s a need for curating collections of files within WordPress, not necessarily as media which will be displayed, but simply as files.
This plugin adds an abstraction called “file groups” to WordPress. Each file group can contain multiple files, which are presented elegantly to the user. All files in a file group can be downloaded together as a zip archive as well.
In addition, file groups can be tagged and these tags are used to associate particular file groups to your posts. Two widgets, “related file groups” and “upload related file group”, are supplied to make it easier to integrate the display of related file groups with your posts.
The plugin currently uses the PHP <a href="http://php.net/manual/en/class.ziparchive.php" rel="nofollow ugc">ZipArchive extension</a> to support the batch download functionality.
This plugin is a component of the <a href="http://ecs.mit.edu" rel="nofollow ugc">MIT Educational Collaboration Space</a> project.
<h3>Migration</h3>
File Groups has some tools which make it easy for you to migrate files which are not in file groups (known as “orphans”) into file groups.
First things first, you will need to (temporarily) unhide the native Media Library from your admin by adding the following to your <code>wp-config.php</code> file:
<pre><code> define( 'FILE_GROUPS_HIDE_NATIVE_MEDIA', false );
</code></pre>
In the Media Library, you will now see a drop down which will let you “show only orphans”. Select any collection of files there which you would like to migrate into a file group, and then select the “create new file group” action from the “Bulk actions” menu and click “apply”. A new file group will be created for the files you selected.
Alternatively, individual orphan files have an action called “create singleton group” available to them if you hover over its row in the table.

File Groups

Add "file group" multiple file handling capability.

Media Auto Hash Rename vs File Groups