Jump to any demo below. Every illusion runs in your browser; nothing is uploaded. Drag sliders to see the effect weaken or strengthen, then use Save / Share to download a watermarked image.
In the Munker–White illusion (White effect), two vertical columns use the exact same gray (#939393). Column A appears only on white horizontal stripes; column B appears only on black stripes. Your visual system assimilates each patch toward the surrounding stripe lightness—A looks lighter, B looks darker. Uncheck “Show black stripes” and every row turns white: the two columns line up as one continuous, identical gray—proof the paint never changed.
Columns A and B use identical gray. Hide black stripes to see they match perfectly.
The Hermann grid (1870) makes ghostly gray dots appear at white intersections between black squares—especially in peripheral vision. Lateral inhibition in the retina is the usual explanation: more white at a crossing suppresses the signal, so the crossing looks dim. Increase gap size or round the squares into circles and the phantoms often vanish—great for classroom experiments.
Use peripheral vision on the white crossings—gray ghosts should appear until gap or radius removes them.
Richard Gregory’s café wall illusion (1973) shows parallel mortar lines that look tilted or wavy when rows of black-and-white tiles are staggered by half a tile. Border locking and brightness induction in narrow mortar strips are leading explanations. Align the rows (shift at 0%) and the lines look straight; toggle “hide tiles” to prove the horizontals are truly parallel.
The Ebbinghaus illusion (Titchener circles) makes each target look larger or smaller depending on surrounding inducer circles—even though both targets share the same pixel size. Uncheck “Show context circles” to reveal dashed alignment lines proving the left and right targets match; labels read “Left target” and “Right target” because which side looks bigger flips as you adjust the sliders.
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Edward Adelson’s checker-shadow illusion places two squares labeled A and B on a checkerboard. Both use the same gray (#787878), but a soft shadow from a green cylinder makes A in shadow look darker than B in light. Toggle the shadow off—or reveal the orange connector—to prove the pixels never changed; your brain discounts illumination.
Squares A and B use identical gray. Hide the shadow or show the connector to compare.
The Müller-Lyer illusion pairs two horizontal lines of equal length. Inward arrow fins (>——<) make a line look shorter; outward fins (<——>) make it look longer. Drag fin length and angle to amplify or weaken the effect—classic misjudgment of metric length from local contour cues.
In the Ponzo illusion, converging “railroad track” lines suggest depth. Two horizontal bars share the same pixel width, but the upper bar sits where the tracks look closer together, so it appears longer. Increase convergence or shift bar height to feel the depth cue strengthen or fade.
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