A TN3270 terminal for retro mainframe hobbyists, on macOS, Linux and Windows. Connect to MVS 3.8j (TK4-, TK5, MVS/CE), VM/370 or z/OS over plain TN3270 or TLS, log on, work in TSO or CMS, and move files with IND$FILE — in one consistent app on every platform, with nothing else to install.
LizTerm's emulation comes from b3270, part of the long-established x3270 suite, which every build bundles.
LizTerm is the modern client around it.
LizTerm is named after Liz, a beloved cat who passed away in December 2021. She liked to sit on my desk beside the keyboard while I worked. She was my mainframe cat.
Her photo is in the app too, under About LizTerm.
- One app, six builds: macOS (Apple Silicon and Intel), Linux (x64 and ARM64) and Windows (x64 and ARM64), each self-contained.
- Session profiles for your hosts, or Quick Connect to try a host without saving one.
- TLS, with certificate verification against your system's trusted roots, and certificate pinning for the self-signed certificates most hobbyist hosts use (pinning is not available on the Windows build — see Known limitations).
- IND$FILE file transfer to and from TSO (at READY or inside ISPF), VM/CMS and CICS, with progress and cancel.
- mvsMF Access, dataset and member access over mvsMF (feature preview), for any MVS 3.8j host running mvsMF 1.1.0 or later: sign in once, then create, rename, list, download, upload and delete datasets and members without touching the 3270 screen.
- Models 2 to 5 in colour (3279) or mono (3278) green phosphor, custom oversize screens, extended colour, and 41 host code pages.
- A Vista TN3270-style keyboard you can remap key by key under Preferences > Keyboard, rectangular selection, and margin-aware paste.
- An on-screen keypad for PF1–PF24, PA1–PA3, Attn, Clear, Reset and the rest, docked to the bottom or the right of the window, and the PF1–PF24 rows can be hidden when your keyboard's F-keys already cover them.
- Find on screen, a crosshair cursor, and screen capture to text or HTML.
- A session switcher (Cmd/Ctrl+K), a Window menu and, on macOS, a Dock menu for finding the right session among many, with Keep on Top for a console you want in view.
- A bell you can see, hear, or both (the sound is macOS and Windows only).
- Keep-alive and automatic reconnect.
- Update notices when a newer release is out, from one request to GitHub at startup that you can turn off.
- Preferences for the crosshair, blinking text, the bell, the keypad, the splash screen, the update check, the close confirmation and your keyboard bindings, and — on macOS — whether the menu is the system menu bar, the one inside the window, or both.
- The IBM 3270 font, on the screen and in the status bar.
LizTerm is pre-1.0. Settings, profile file formats, defaults and interfaces may change between releases.
The 3270 emulation is not new code. It is b3270, from the long-established x3270 suite, which every build
bundles. LizTerm builds it from the upstream source with one small addition of its own, so a file transfer can start
from inside ISPF. That part of the stack is mature, and it is not where the risk is. What is new is the client around
it — the window, profiles, settings, the file-transfer interface and the packaging. Expect the terminal session itself
to be solid, and rough edges in the application surrounding it.
If you find one, please open an issue.
Get the latest build from the Releases page. The ZIP for your platform is the simplest choice: unpack it and run LizTerm. The installers beside it are the same app, for people who prefer one.
| Platform | Archive | Installer |
|---|---|---|
| macOS, Apple Silicon | LizTerm-osx-arm64-<version>.zip |
.dmg |
| macOS, Intel | LizTerm-osx-x64-<version>.zip |
.dmg |
| Linux x86-64 | LizTerm-linux-x64-<version>.zip |
.deb, .rpm |
| Linux ARM64 | LizTerm-linux-arm64-<version>.zip |
.deb, .rpm |
| Windows x64 | LizTerm-win-x64-<version>.zip |
.exe |
| Windows ARM64 | LizTerm-win-arm64-<version>.zip |
.exe |
Inside each ZIP the app is LizTerm.app on macOS, LizTerm.App on Linux, and LizTerm.App.exe on Windows. Linux
builds need glibc 2.28 or newer, the same floor as .NET 10 itself; musl distributions such as Alpine are not
supported. Windows ARM64 builds bundle the x64 b3270 engine, which runs under Windows 11's x64 emulation; the app
itself is native ARM64.
macOS builds are signed and notarized by Apple, so LizTerm opens like any other app you download. The first time, macOS may ask you to confirm that you want to open something downloaded from the internet.
Windows: SmartScreen warns that the publisher is unknown. Choose More info, then Run anyway.
- Open LizTerm. After the splash screen — which you can turn off later — you'll see the Sessions list.
- Choose New..., give the profile a name, and enter the host and port. Tick Use TLS if the host needs it, then Save.
- Select the profile and choose Connect.
To try a host without saving a profile, type its address into the Quick Connect box — for example
mvs.example.org, 192.168.1.10:3270, or L:mvs.example.org for TLS. Once connected, File > Save as Profile... keeps it.
If your host uses a self-signed certificate, as most hobbyist hosts do, LizTerm asks what to do the first time. See TLS and certificates.
A few keys to know straight away:
- Escape is Attn, not Reset. Reset is a tap of the Left Ctrl key, or Ctrl+R.
- Clear is Pause, or Ctrl+Escape — on Windows, where Ctrl+Escape opens the Start menu, it is Pause.
- F1–F12 are PF1–PF12; add Shift for PF13–PF24.
The user guide has the full keyboard map and everything else.
Please open an issue. A wire log helps a lot: turn on Help > Wire Log in the session window, reproduce the problem, turn it off, and attach the file (Help > Show Wire Logs... opens the folder). A wire log records everything you type, including passwords, so check it before you share it.
LizTerm is open source under the BSD 3-Clause License, Copyright 2026 by CoffeeMuse. See LICENSE.
The photo of Liz is the exception: it is under CC BY-NC-ND 4.0, so you may share it unchanged and with credit, but not commercially (notice).
It bundles:
- x3270 / b3270: BSD-3-Clause, Copyright Paul Mattes and others.
- The IBM 3270 font by Ricardo Banffy: SIL Open Font License 1.1 (licence).
- Avalonia and CommunityToolkit.Mvvm: MIT.
Their notices are in THIRD-PARTY-NOTICES.txt. Every build shows LizTerm's licence and these notices in full under About LizTerm — in a session window's Help menu, or the LizTerm menu on macOS.
- User guide: keyboard, profiles, TLS, file transfer, mvsMF Access, screen capture, wire logs.
- Changelog: what changed in each release.
- Development: building from source, tests, conventions.
- Engines: how the bundled b3270 is built and verified.
- CI and release: workflows, packaging, signing.
- Architecture: how the pieces fit together.