aTalk is an XMPP client designed for Android that supports the following features: - Instant messaging in plain text and end-to-end encryption with OMEMO. - SSL certificate authentication, DNSSEC, and DANE security implementation for enhanced secure connection establishment. - OMEMO encryption in group chat sessions to enhance privacy and security. - OMEMO media file sharing for all files, including stickers, Bitmoji, and emoji-rich content. - HTTP file upload support for sharing files with offline contacts and in group chats. - Sticker, Bitmoji, and emoji-rich content sharing via Google Gboard. - Send and receive files of all document types and images, with thumbnail previews and GIF animation. - Auto-accept file transfers with a maximum file size option. - Fault-tolerant file transfer algorithm via HTTP File Upload, Jingle File Transfer, and legacy in-band/SOCKS5 bytestreams protocols to improve file sharing reliability. - Secure file transfer via HTTP File Upload using aesgcm:// or via Jingle Encrypted Transport (JET). - Enhanced and harmonized UI for file sharing in chats and chat rooms. - Share, quote, and forward messages and media with previews before sending. - Multi-instance audio media player with play, pause, resume, stop, and seek functions. - Unread message badges in contact and chat room list views. - User-selectable heads-up notifications and quiet hours. - Social media link sharing tagged with thumbnails and titles. - Text-to-speech and speech recognition UI with per-chat-session enable option (for contacts and group chats). - XEP-0012: Last Activity (time associated with contacts). - XEP-0048: Bookmarks for conference rooms with auto-join on login. - XEP-0070: Verifying HTTP requests via XMPP entity for user authentication without password entry. - XEP-0071: XHTML-IM support for chat messages with lightweight text markup. - XEP-0085: Chat State Notifications. - XEP-0124: Bidirectional-streams Over Synchronous HTTP (BOSH) with proxy support. - XEP-0178: Use of SASL EXTERNAL with TLS certificates for client authentication. - XEP-0184: Message Delivery Receipts with user enable/disable option. - XEP-0215: External Service Discovery. - XEP-0251: Jingle Session Transfer (support for both unattended and attended call transfer). - XEP-0313: Message Archive Management. - XEP-0391: Jingle Encrypted Transports for OMEMO-encrypted media file sharing. - Call waiting to accept a second incoming call by placing the in-progress call on hold, with switching between calls. - Jabber VoIP-PBX gateway telephony, allowing PBX phone calls via a service gateway. - Join or create rooms with full configuration support for owners. - Integrated CAPTCHA-protected room UI with retry on failure. - Support for both voice and video calls with ZRTP, SDES, and DTLS-SRTP encryption modes. - ZRTP crypto algorithms using SHA-2 (384/256-bit ciphers AES-256 & TWOFISH-256, with elliptic Curve25519). - SDES encryption with AES-256 and AES-192, accelerated using OpenSSL. - Simultaneous media calls and message chat sessions. - Unique GPS location implementation as a standalone tool; send locations to buddies for real-time tracking or playback animation. - 360° street view of your current location for self-guided tours (tracks and follows your direction of sight). - Built-in demo for GPS location features. - Integrated photo editor with zooming and cropping; easily update your avatar. - Last message correction, message carbons, and offline messages (OMEMO). - Stream Management and mobile network ping interval self-tuning optimization. - In-band registration with CAPTCHA option support. - Multiple account creation. - User-selectable themes. - Multi-language UI support (Arabic, Bahasa Indonesia, Chinese Simplified, English, Finnish, German, Portuguese (Brazil), Russian, Slovak, Spanish).