Optical Illusions Gallery – See What Is Really Equal or Parallel
Lines that look unequal, parallel lines that seem to bend: here are nine classic illusions. Show guide lines or hide the part that causes the effect to prove that your eyes are being fooled. There is no flashing or fast motion. For color and perception, you might also like the Color Contrast Checker or Memory Match.
🔒 Runs in your browser · Your data is never sent to a server
Strength cannot be changed for this illusion.
Müller-Lyer illusion
What you see: The bottom line (with outward fins) looks longer than the top one (with arrowheads).
What is true: Both lines have exactly the same length. The guide lines show that their ends line up.
Ponzo illusion
What you see: Between two lines that converge into the distance, the upper bar looks longer.
What is true: The two bars are the same length. With depth cues, your brain judges the farther one to be bigger.
Zöllner illusion
What you see: Horizontal lines with short slanted ticks seem to tilt toward each other.
What is true: The four long lines are perfectly parallel. Hide the ticks to see how straight they are.
Ebbinghaus illusion
What you see: The center circle surrounded by big circles looks smaller than the one surrounded by small circles.
What is true: The two orange circles are the same size. The guide lines are tangent to both at the top and bottom.
Café wall illusion
What you see: Black and white tiles shifted row by row make the gray mortar lines look slanted.
What is true: The mortar lines are straight and horizontal. Show the guide lines, or set the strength to 0, to check.
Checker shadow illusion
What you see: Square A, inside the shadow, looks much lighter than square B, outside it.
What is true: A and B are the same shade of gray. The guide band joins them in one color. Your brain discounts the shadow when judging brightness.
Hermann grid illusion
What you see: Faint gray spots seem to appear at the white crossings between the black squares.
What is true: The crossings are as white as the lanes. The spot disappears at the crossing you look at directly.
Poggendorff illusion
What you see: A diagonal line hidden behind a bar seems to come out shifted on the other side.
What is true: The two segments lie on one straight line. Show the guide line to see that it connects perfectly.
Fraser spiral illusion
What you see: Concentric circles look like a swirling spiral.
What is true: All four are perfect concentric circles. Trace the guide circles to see that the swirl lies on a circle.
How to use
- Pick a figure in "Illusion". "Next illusion" cycles through them in order.
- First, judge by eye which lines are longer, or whether they are parallel.
- Turn on "Show guide lines" to confirm that they really are equal or parallel.
- Use "Hide illusion cause" to remove what triggers the effect, or "Strength" to change how strong it is, and compare.
Notes
- Every figure is drawn as SVG on this page. Nothing is loaded or sent to a server.
- For people sensitive to light, the page uses no flashing or fast motion. If you feel uncomfortable, look away from the screen.
- What you see varies between people and with screen size, brightness and viewing distance. Some illusions may look weak.
- Illusions come from normal workings of the eyes and brain. This page is not a tool for testing eyesight or diagnosing anything.
Glossary
Optical illusion
A visual effect where size, length, direction or brightness looks different from what it really is. It arises from the brain’s normal attempts to correct what it sees using context.
FAQ
Which illusions are included?
Nine: Müller-Lyer, Ponzo, Zöllner, Ebbinghaus, café wall, checker shadow, Hermann grid, Poggendorff and the Fraser spiral. Each comes with a short note on what you see and what is actually true.
What do the guide lines show?
They are lines or bands that prove the effect is only apparent: equal length, parallel, collinear or the same color. For Müller-Lyer they align the line ends, and for the checker shadow a band of one gray joins A and B.
The illusion looks weak to me. Is that normal?
Yes. How strong an illusion looks differs between people, and it also depends on screen size, brightness and viewing distance. Try the "Strength" slider. The checker shadow figure is fixed, so strength does not apply to it.
Is it safe for people who are sensitive to light?
The page has no flashing and no fast animation, and every figure is still. Some people still find staring at patterns uncomfortable, so look away from the screen if you start to feel unwell.
Can I save or print the figures?
There is no image export. Use your browser’s print function or a screenshot if you need a copy. The figures are drawn on the page itself and nothing is sent anywhere.
Share this page