Technical Glossary

Human-Machine Interface (HMI)

Definition, types, examples and differences with UI — everything you need to know about HMI.

A Human-Machine Interface (HMI) refers to all the devices — visual, tactile, auditory or gestural — that allow a human user to interact with a computer, electronic or mechanical system. It is the point of contact between the internal logic of a machine and the intention of a user.

The main types of HMI

Human-machine interfaces fall into several broad categories depending on the interaction channel used.

Graphical interfaces (GUI)

Windows, buttons, drop-down menus, icons — the classic visual interfaces of operating systems and software.

Touchscreen interfaces

Capacitive screens on smartphones, tablets and interactive kiosks enabling interaction through touch.

Voice interfaces

Voice assistants (Siri, Alexa, Google Assistant) and speech recognition systems.

Industrial HMI

Control panels, programmable logic controllers and SCADA systems used in production environments.

Immersive interfaces

Virtual reality (VR) and augmented reality (AR) for interactions in three-dimensional environments.

Command-line interfaces

Terminal, shell, CLI — direct text-based interaction with the operating system or software.

HMI, UI, GUI: what are the differences?

These terms are often confused. Here are their key distinctions.

Term	Meaning	Usage context
HMI	Human-Machine Interface	Generic term used in computing, industry and ergonomics.
IHM	Interface Homme-Machine	French equivalent, widely used in French-speaking technical and industrial contexts.
UI	User Interface	Term from digital design, often limited to software and web interfaces.
GUI	Graphical User Interface	HMI subcategory: fully visual interfaces (windows, icons, pointer).
UX	User Experience	Refers to the overall user experience, beyond the visual interface alone.

Why is HMI essential?

A well-designed HMI reduces human error, improves productivity and makes systems accessible to the widest possible audience. It is at the heart of disciplines such as cognitive ergonomics, systems engineering and UX design.

In industry, a poorly designed HMI can have serious consequences (accidents, failures). In the digital world, it directly determines the adoption rate of a software product.

Frequently asked questions about HMI

What is the simple definition of an HMI?

An HMI is anything that allows a human to communicate with a machine: a screen, a keyboard, a voice, a physical button or a gesture. It is the “translator” between the human and the machine logic.
What is the difference between an HMI and a user interface (UI)?

HMI is the broader term: it covers all forms of interaction (industrial, vocal, gestural…). The UI (user interface) is a subcategory of HMI, generally limited to digital and visual interfaces.
What are concrete examples of HMI?

An ATM, a smartphone interface, a car dashboard, a warehouse management system, a voice assistant or the numerical control of a machine tool are all examples of HMI.
Who designs human-machine interfaces?

HMI design involves several profiles: ergonomics engineers, UX/UI designers, software developers and, in industry, automation engineers or systems engineers. Standards such as ISO 9241 set out best practices for design.