CrushFTP is a proprietary multi-protocol, multi-platform file transfer server originally developed in 1999.  CrushFTP is shareware with a tiered pricing model.  It is targeted at home users on up to enterprise users.
 CrushFTP supports the following protocols: FTP, FTPS, SFTP, HTTP, HTTPS, WebDAV and WebDAV SSL.  Additionally, although not a protocol, it has both AJAX/HTML5 and Java applet web interfaces for end users to manage their files from a web browser.  CrushFTP uses a GUI for administration, but also installs as a daemon on Mac OS X, Linux, Unix, and as a service in Windows.  It supports multihoming, multiple websites with distinct branding, hot configuration changes, Attachment redirection, and GUI-based management of users and groups from a browser.  Plugins are included for authentication against SQL databases, LDAP, Active Directory, and other custom methods.  All settings are stored in XML files that can be edited directly, or with the web UI.  If edited directly, CrushFTP notices the modification timestamp change and load the settings immediately without needing a server restart.
 CrushFTP was first published publicly around 1998.  Initial versions were FTP only.  There were no connection restrictions in version 1.x.  CrushFTP 2.x brought about virtual directories in a sense, while CrushFTP 3.x  brought about a full virtual file system.  It supported the ability to merge and mangle several file systems together regardless if they were from local folders, or another FTP site.  It could even act as a proxy for other FTP servers.  However the complications from all the potential issues that could go on from this was confusing.  CrushFTP 3 introduced tiered pricing models.
 CrushFTP 4 focused primarily on a cleaner interface and less confusing virtual file system.  While it still seems to have some support for merging FTP sites with a local file system, the support seems limited.  Updates in version 4 included a full HTTP server as well as the other supported protocols.  Later updates began recognizing connection differences between web browsers and FTP/SFTP clients, counting four web browser connections as only one user against the licensed limit.
  CrushFTP 5 continued the evolution of the WebInterface with various iterations.  It used a  flash interface briefly before replacing it with a HTML/AJAX interface.  CrushFTPv5 was the last version to still use a thick client Java Swing UI.  Version 6 moved to an all web browser UI.
  CrushFTP 6 released in 2012 brought about major changes as the management and monitoring interface became entirely web based.  Its interface is based on jQuery and jQuery UI.  Multiple administrators can work concurrently, fixing the single admin limitation of prior versions.  It had image thumbnail support and file replication and synching.
 CrushFTP 7 was released in early 2014.  According to the "what's new" page it adds a dashboard for server information, delegated role based administration, graphical job / event designer, MP4 movie streaming support using HTML5, UPnP / PMP port forwarding and automatic external port validation testing, among many other features.  Some features are available only to enterprise customers such as user synchronization and DMZ prefs synchronization between internal servers.
 CrushFTP 8 was released in late 2016.  The "what's new" page lists a new faster HTML5 browser uploading system (4x faster) with resume support, a limited filesystem server mode, and data replication as key new features.  There is a revision system on files, a new reports UI, and a stand-alone client UI as part of the release as well.
 CrushFTP 9 was released in late 2018.  The "what's new" page lists a new CrushBalance load balancer, new Citrix protocol for VFS, uses fewer threads, [Let's Encrypt] plugin support, automated expiration reminder emails for passwords, accounts, and shares. Additionally it lists Proxy Protocol v2 support for AWS load balancers, and an enhanced Job management system.
 CrushFTP 10 was released in early 2021.
 Encryption is supported for files "at rest" using PGP, as well as for passwords using an MD5 or SHA, SHA512, SHA3, MD4 non-reversible hash.  SFTP uses SSH for encryption, and FTPS uses SSL/TLS for encryption. SHA-2 hashing algorithms are supported.  Hashes can be salted with random salt values.
 As August 2021, there has been six published vulnerabilities in CrushFTP.