Terminal Capabilities¶

What an enterprise 3270 terminal is expected to do, and what 3270Web provides. Every capability below is implemented and shipping — the tables are a checklist you can take into an evaluation, not a roadmap.

For how 3270Web compares with the other emulators in this category, and for what may come next, see the Feature Roadmap.

Terminal fidelity¶

Behaviour an experienced 3270 operator expects from the terminal itself. This is not feature count — it is whether the thing behaves like a terminal.

Capability	3270Web
TN3270 and TN3270E, with TLS	✅
Full AID and control key coverage — PF1–24, PA1–3, Attn, SysReq, Clear, Reset, EraseEOF, EraseInput, Dup, FieldMark, NewLine, Home	✅
Extended colour, blink, reverse video, underscore, intensify	✅
Operator Information Area — online/application block, `X SYSTEM`, `X -f` operator error, insert indicator	✅
Local cursor movement — Tab, Back-Tab, arrows and Home resolve in the client, with no host round-trip	✅
A cursor that can rest anywhere on the display, protected text included, for cursor-position-driven screens	✅
Numeric field enforcement, with a real operator-error lock	✅
Auto-skip driven by the field attributes the application sends, not by guesswork	✅
Insert / overtype toggle	✅
Type-ahead while the host holds the keyboard	✅
Selectable terminal models and screen sizes	✅
Code page selection per connection	✅
The characters those code pages are chosen for — pound signs, umlauts, accents, Cyrillic and Greek — drawn on the screen and accepted into a field	✅
The host's own code points readable over the API, so a code page complaint is settled against the byte the host sent rather than against the character it became	✅

On a 3270 the cursor belongs to the terminal, and the host learns its position exactly once — in the inbound data stream, when an AID key is pressed. 3270Web models it the same way, which is what removes a network round-trip from every Tab and arrow keypress. See Keyboard and Controls.

Screen tools¶

Capability	3270Web
Screen-accurate copy, including unsubmitted input and excluding hidden fields	✅
Rectangular block copy — Alt+drag to mark, Ctrl+C to take	✅
Find on screen, over the character grid so it matches input values too	✅
Screen history / scrollback — the last 50 screens per session	✅
Hotspots — clickable PF/PA legends and URLs printed by the application	✅
Print screen	✅
Focus mode — the terminal fills the display, with an auto-hiding menu rail	✅
Business and Engineering workspace modes	✅
Command palette over every control	✅

Find and copy both run on the character grid rather than the DOM, so they see what the screen actually shows — including values someone has typed but not yet submitted, which the browser's own find and selection cannot reach.

Sessions and connections¶

Capability	3270Web
Multiple concurrent sessions in one browser, with a tab bar	✅
Named connection profiles, stored server-side	✅
Per-connection TLS, certificate verification, LU name, model and code page	✅
Auto-reconnect on host drop, with a manual Reconnect	✅
Session timeout handling with a clear prompt	✅
Graceful host disconnect on teardown, rather than dropping the connection	✅
Connection introspection — negotiated telnet options, TLS state, terminal name, byte counts — in the UI and on the API	✅

Connection profiles are server-side rather than browser-local, because connection settings are what an administrator sets up once for everyone. Most of a profile becomes s3270's own target syntax, which the UI shows verbatim, so what you check is what gets dialled.

Keyboard¶

Capability	3270Web
Customisable keyboard mapping	✅
Rebind by pressing the key, not by choosing from a list of key names	✅
Custom bindings layer over the built-ins rather than replacing them	✅
Export and import a layout as JSON	✅
Import an existing `.KMP` keyboard file	✅
Virtual keypad, in compact, full and maximum layouts	✅
Touch: AID keys within a thumb's reach, above the software keyboard	✅
Touch: tap the screen to place the cursor, protected cells included	✅

File transfer¶

Capability	3270Web
IND$FILE send and receive	✅
Text and binary modes, with line-ending handling	✅
TSO, VM and CICS host types	✅
Dataset creation options — record format, record length, block size, space allocation	✅
PDS member names (`USER.DATA(MEMBER)`)	✅

Printer sessions¶

Capability	3270Web
3287 printer emulation — LU1 (SCS) and LU3 (3270) datastreams	✅
Bind a named printer LU, or the printer associated with the display LU	✅
Printer session follows the terminal's host, port and TLS terms	✅
Jobs collected as files, downloadable from the browser or the API	✅
Line length, code page, carriage control, formfeed and end-of-job handling	✅
Printing to a printer physically attached to the operator's machine	❌

The last row is the honest one, and it is what a browser trades away everywhere else too: the job reaches the browser as a file, and what happens after that is the operating system's business. See Printer sessions.

Accessibility¶

Capability	3270Web
Screen-reader field labelling derived from the screen's own label text	✅
Keyboard-only operation	✅
Keyboard-trap escape hatch (WCAG 2.1.2)	✅
High-contrast and themeable rendering, seven built-in themes	✅
Reduced-motion support	✅
WCAG 2.1 AA conformance statement, from a tested audit	✅

See Accessibility for the conformance statement — what was tested, what conforms, and what does not.

Field labelling is worth calling out. 3270Web derives each input's aria-label from the protected text to its left, so a screen reader announces "Customer number, edit text" rather than "edit text" — the difference between a usable screen and an unusable one.

Beyond the category baseline¶

These are not table stakes anywhere. They are the reason to choose 3270Web rather than merely tolerate it.

Capability	3270Web
Runs in a browser tab — no emulator install, no thick client	✅
Public REST/JSON API for RPA and CI integration	✅
Workflow recording and playback, with pause, step and debug	✅
Decisions in a recording — read a value off the screen, branch on it, repeat a group of steps while a condition holds	✅
Guided Business Tasks — run a recorded flow from a form and get an answer, no green screen	✅
Task authoring from a recording — record once, mark the answer, save to a shared catalogue	✅
Task authoring from a chaos run — convert a discovered path into a runnable task	✅
Chaos exploration — automated discovery of an application's screens and transitions	✅
Screen mind-map, exportable and diffable between hosts	✅
Screen snapshots, diffed row by row — regression testing against a green screen	✅
Screen tracing — every screen recorded as it is drawn, including the ones replaced before anyone looked	✅
Embeddable in another application's page, with a documented postMessage channel	✅
HLLAPI-shaped endpoint for porting existing screen-scrapers	✅
Macro-file import — an existing macro becomes a recording, branches and loops included, with every line it could not translate reported	✅
Host compatibility profiler	✅
AI Chat driving the host through a documented tool surface	✅
Docker image and a one-line installer	✅

Guided Business Tasks are the one that changes who can use the product: a task has named inputs and a named answer, so the person running it needs to know the business question rather than the application. See Guided Business Tasks.

The REST API and the workflow JSON are paired deliberately: a flow recorded by hand in the browser is the same document an automated job replays, so there is no separate scripting language to learn and no gap between what a person did and what a bot repeats. See REST API, Recordings and Playback and Chaos Mode.