#I2PChat(formerly I2P - Messenger)

End-to-end encrypted peer-to-peer messenger over I2P. Uses the SAM bridge for anonymous, serverless communication with full file transfer support.

Screenshots

Features

• Peer-to-peer messaging and file transfer over I2P — no central server
• End-to-end encryption via I2P's garlic routing
• Contact list with online status indicators (Online, Away, Invisible, Do Not Disturb)
• Userlist sorting — alphabetically, by date added, last communication, or last online
• Online visibility control per contact (visible, hidden, blocked)
• Request authorization dialog for new incoming connections
• Transient (non-persistent) identity option for session-only keys
• Auto-away detection with configurable timeout
• Inline pending messages — compose while offline, sent automatically on reconnection
• Emoticon support with punctuation-boundary detection
• Automatic URL linking in chat messages
• Optional b32.i2p web profile page with avatar, bio, and interests
• Multi-file static web server hosted at your b32.i2p address — drop files in ~/.i2pchat/www/
• File transfer with per-user auto-download configuration and pipelined transfers
• Drag-and-drop image upload with inline display
• Copy b32 address and raw destination with right-click
• Move contacts to top/bottom of list via right-click menu
• Offline message queue — messages are delivered when the contact comes online
• Offline file-offer queue — select files while offline, recipient gets Accept/Reject links on reconnect; accepted offers start a live file transfer
• Cancel pending messages and file offers before they're sent with a click
• Configurable tunnel length, quantity, and backup quantities
• ECIES (Ratchet) and EdDSA signature types for new destinations
• Customizable chat appearance (font, color, style)
• Sound notifications for online/offline, messages, and file transfers
• Debug logging for troubleshooting

Build instructions

Dependencies

Qt 5.14+ or Qt 6.2+ is required.

Debian / Ubuntu (including 24.04+, trixie+)

Qt 5:

sudo apt-get install -y build-essential qt5-qmake qtbase5-dev qtmultimedia5-dev libqt5svg5-dev

Qt 6:

sudo apt-get install -y build-essential qmake6 qt6-base-dev qt6-multimedia-dev qt6-svg-dev

Fedora

Qt 5:

sudo dnf install make qt5-qtmultimedia-devel qt5-qtsvg-devel qt5-qtbase-devel

Qt 6:

sudo dnf install make qt6-qtmultimedia-devel qt6-qtsvg-devel qt6-qtbase-devel

Windows cross-compile (x86_64 / 64-bit only, via MinGW-w64)

bash build.sh --windows auto-clones MXE to tools/mxe/ and builds the qt5 target (x86_64-w64-mingw32.static) on first run (static toolchain + Qt5, takes a while). Subsequent builds reuse the cached toolchain automatically.

Optional build tools

build.sh checks these dynamically — only needed when using the corresponding flag:

Tool	Flag	Install
clang-format	--format	apt install clang-format / dnf install clang-tools-extra
clang-tidy, run-clang-tidy	--tidy	apt install clang-tidy / dnf install clang-tools-extra
bear or compiledb	(compile_commands.json)	apt install bear / pipx install compiledb (for clang-tidy, clangd, etc.)
wget + linuxdeploy	--appimage	apt install wget / dnf install wget (linuxdeploy downloaded automatically)
upx	--upx	apt install upx / dnf install upx
dpkg-deb	--deb	apt install dpkg (pre-installed on Debian/Ubuntu)
MXE + qt5 target	--windows	Auto-cloned — needs gperf, libtool + libtool-bin (Debian) on the host

Quick build

bash build.sh

Run bash build.sh --help for all options (incremental by default, --clean for full rebuild, --format and --tidy for linting, --appimage for a portable AppImage, --deb for a .deb package, --windows to cross-compile a Windows .exe, --upx to compress the binary with UPX).

Qt 6

Qt 6 support lives on the qt6 branch. To build with Qt 6:

git checkout qt6
qmake6 I2PChat.pro
make -j$(nproc)

The qt6 branch is periodically merged from master and includes fixes for all Qt 6 deprecations and API changes.

Manual compilation

Qt 5:

qmake I2PChat.pro "CONFIG += release"
make -j$(nproc)

Qt 6:

qmake6 I2PChat.pro
make -j$(nproc)

Downloads

• CI builds (all platforms) — Linux, Windows, macOS

Running

On Linux, bash build.sh creates a stripped binary at dist/I2PChat. Run bash build.sh --appimage to produce a portable AppImage at dist/I2PChat-x86_64.AppImage. Run bash build.sh --deb to produce a .deb package at dist/i2pchat_<version>_<arch>.deb. Manual builds produce I2PChat in the project root. Run it with ./I2PChat.

On Windows, cross-compile from Linux via bash build.sh --windows (64‑bit only, requires MXE with qt5). The .exe is written to dist/I2PChat.exe. No Windows SDK needed.

On macOS, the CI produces a bundled .app via macdeployqt. Run it by double-clicking I2PChat.app.

• Enable the SAM application bridge in your router: Java I2P via Client Configuration, or i2pd via i2pd.conf's [SAM] section.
• Select Online from the dropdown menu on the main window. Your unique I2P destination is created automatically on first SAM connection.
• Settings and contacts are stored in ~/.i2pchat/ (Linux) or %APPDATA%\Roaming\I2PChat\ (Windows).
• Default signature type: EdDSA_SHA512_Ed25519. DSA_SHA1 is no longer available.

Sounds

I2PChat plays notification sounds for online/offline events, incoming messages, and file transfers.

Debian/Ubuntu (.deb): Sounds are included and automatically copied to ~/.i2pchat/sounds/ on first run.

Other platforms: Download the sounds archive and extract to the config directory:

Platform	Config path
Linux	~/.i2pchat/sounds/
Windows	%APPDATA%\Roaming\I2PChat\sounds\
macOS	~/Library/Application Support/I2PChat/sounds/

Sound files can be customized by editing the paths in application.ini under [Sound][SoundFilePath].

Web Server

When enabled, I2PChat serves files from ~/.i2pchat/www/ (or a custom docroot) over I2P on your b32.i2p address. The web server supports multi-user access with HTTP Basic Auth, per-user folder mapping, cookie-based sessions, directory listing, and rate-limited login attempts.

Setting	Default	Behavior
Web server	Enabled	Master toggle; hides page when any contact is invisible
Require login	Disabled	When ON, all requests challenge for credentials
Directory listing	Disabled	Show file index when no index.html exists
Session timeout	60 min	Cookie lifetime; expired sessions require re-login
Users	—	Per-user username/password and document root folder

Auth modes:

• Login not required (default): All paths are public. Visit b32.i2p/login to authenticate; once authenticated via Basic Auth, a session cookie is set and your per-user folder is served. /logout clears the session and returns to the public root.
• Login required: Every request challenges with 401. After successful auth a session cookie avoids re-prompting. /logout challenges again.

Rate limiting: 3 failed login attempts per I2P destination triggers a 1-hour ban (persisted across restarts in bans.txt).

Security model:

• Path traversal is blocked at every level: QDir::cleanPath normalization, null-byte rejection, and canonical-path boundary enforcement that follows symlink resolution
• Only GET and HEAD methods are accepted; all others receive 405
• Request headers over 4KB are rejected (DoS mitigation)
• Username token injection strips < and > characters (XSS prevention)
• Content-Security-Policy is set restrictively (default-src 'self', form-action 'none', base-uri 'none', frame-ancestors 'none'). Users may override via <meta> tags in their HTML
• Symlinks inside www/ are rejected (must be regular files)
• Session cookies are HttpOnly + SameSite=Lax
• HTTPS is not applicable — transport security is provided by I2P's garlic routing at the network layer

Changelog

See docs/CHANGELOG.md.

License

Licensed under AGPL-3.0-or-later. Originally forked from I2P-Messenger (GPL-2.0-or-later).