Usability Harness
Simulators, experiments and checks for testing a design against the people who will use it. We made them for our own work; you’re welcome to use them too.
Check · for any website
The Good Citizens check: look at what you just shipped
One bookmark that checks any live page for accessibility, speed, type and structure, and says each problem in terms of the person it leaves out.
Open →Simulator · for any website
Screen reader view: the page, read aloud in order
See any page the way a screen reader lays it out: everything in reading order, the headings outline, links, images and form fields, with every problem marked.
Open →Simulator · for any website
LLM view: the page, as an AI model reads it
See any page the way AI models and agents receive it: as text, before JavaScript, as a map of named controls, and with every hidden word showing.
Open →Simulator · for any website
Keyboard only: put the mouse away
Put the mouse away on any page, follow the focus with Tab, and find every control that looks clickable but cannot be reached.
Open →Simulator · for any website
Motion and distraction: what moves, and who it hurts
Find everything on a page that moves or plays by itself, see whether it respects “Reduce motion”, and pause it all.
Open →Instrument · prototype
Fovea: a design as one glance sees it
See a design the way one glance does: sharp only where you look, sized for how far you actually sit from the screen, measured on your own device.
Open →Simulator · for any website
Colour blindness: the same page, seen differently
See any web page the way people with each kind of colour blindness see it, and why colour should never be the only signal.
Open →Simulator · for any website
Ageing eyes: a page through older eyes
See a web page the way eyes see it at 50, 70 and 80, and what that asks of text size, contrast and colour.
Open →Simulator · for any website
A shaky hand: why small targets fail
Try to click small and large targets with a pointer that shakes, and see why target size matters for many people.
Open →Simulator · for any website
A slow connection: when a click takes its time
Feel what happens when every click waits before anything happens, and why a page should answer at once.
Open →Experiment · on you
Better, not wiser: confidence and expertise after AI
AI makes our work better faster than it makes us better judges of it. Take the experiment with and without an assistant, and read what the research found.
Open →Experiment · on you
Fitts’s law: why big, close buttons win
Click targets of different sizes and distances, and see your own times follow Fitts’s law.
Open →Experiment · on you
Hick’s law: more choices, slower decisions
Find a word among 2, 4 or 8 choices, and see how your time grows each time the choices double.
Open →Experiment · on you
Change blindness: why people miss what changed
Spot what changes between two flickering versions of a product card, and see how easily the eye misses a change.
Open →Experiment · on you
Working memory: how much can you carry?
Carry a code from one screen to the next as it grows, and find how many characters you can hold in your head.
Open →