gloox is fully compliant to XMPP Core and almost (see below) fully compliant to XMPP IM. The following are some of the supported features:

• TLS and SASL
• roster management
• privacy lists
• SRV lookups
• server certificate verification
• support for xml:lang i18n

Additionally, the following XEPs are supported:

• XEP-0004 Data Forms
• XEP-0012 Last Activity: complete, experimental
• XEP-0013 Flexible Offline Message Retrieval
• XEP-0022 Message Events
• XEP-0027 Current Jabber OpenPGP Usage
• XEP-0030 Service Discovery
• XEP-0045 Multi-User Chat
• XEP-0047 In-Band Bytestreams
• XEP-0048 Bookmark Storage
• XEP-0049 Private XML Storage
• XEP-0050 Ad-hoc Commands: command provider complete
• XEP-0054 vcard-temp
• XEP-0055 Jabber Search
• XEP-0060 Publish-Subscribe
• XEP-0065 SOCKS5 Bytestreams: TCP mode only for now
• XEP-0066 Out of Band Data
• XEP-0073 Basic IM Protocol Suite
• XEP-0077 In-Band Registration
• XEP-0078 Non-SASL Authentication
• XEP-0079 Advanced Message Processing
• XEP-0083 Nested Roster Groups
• XEP-0085 Chat State Notifications
• XEP-0091 Delayed Delivery (old spec)
• XEP-0092 Software Version
• XEP-0095 Stream Initiation
• XEP-0096 File Transfer
• XEP-0106 JID Escaping
• XEP-0114 Jabber Component Protocol
• XEP-0115 Entity Capabilities
• XEP-0117 Intermediate IM Protocol Suite
• XEP-0124 Bidirectional-streams Over Synchronous HTTP (BOSH)
• XEP-0131 Stanza Headers and Internet Metadata
• XEP-0138 Stream Compression
• XEP-0145 Annotations
• XEP-0153 vCard-Based Avatars
• XEP-0166 Jingle
• XEP-0170 Recommended Order of Stream Feature Negotiation
• XEP-0172 User Nickname
• XEP-0174 Serverless Messaging
• XEP-0176 Jingle ICE-UDP Transport Method
• XEP-0184 Message Receipts
• XEP-0198 Stream Management
• XEP-0199 XMPP Ping
• XEP-0201 Best Practices for Message Threads
• XEP-0203 Delayed Delivery (new spec)
• XEP-0206 XMPP over BOSH
• XEP-0211 XMPP Basic Client 2008
• XEP-0224 Attention
• XEP-0234 Jingle File Transfer
• XEP-0244 IO Data
• XEP-0256 Last Activity in Presence
• XEP-0280 Message Carbons
• XEP-0297 Stanza Forwarding
• XEP-0352 Client State Indication

gloox is known to run at least on Linux, *BSD, MacOS X, SkyOS, Syllable and Win32 (both MingW and MSVC). There also is experimental support for WinCE/Mobile.

Not supported but required by XMPP IM:

• End-to-end object encryption as defined in RFC 3923 (End-to-End Object Encryption in the Extensible Messaging and Presence Protocol (XMPP)): there are no other implementations of the spec
• handling of addresses that are encoded as “im:” URIs: this is better handled by client implementations