Colour Blindness Simulator
Re-renders an image as protanopia, deuteranopia, tritanopia or greyscale vision would see it.
A chart that codes its series by hue alone is unreadable to roughly one man in twelve, and there is no way to notice that by looking at it with typical colour vision. This re-renders the whole image as a dichromat’s eye would receive it, and puts a number on how much separation was lost.
Drop a chart, map or screenshot
The simulation runs on the pixels in this tab.
How to use it
Drop the image
A chart, a map, a heat map or a dashboard screenshot — the cases where the information lives in the hue.
Pick the vision type
Deuteranopia is by far the commonest, at about 1% of men; start there. Tritanopia is rare enough that it is a completeness check rather than a design constraint.
Read the separation figure
It is the mean distance each pixel moved, against the diagonal of the RGB cube. Near zero means the image barely depends on the colours this removes.
Fix it with something other than hue
Different lightness, a dashed versus solid line, a marker shape or a direct label. Any one of them carries the distinction through every simulation here.
Common questions
Is this what colour blindness actually looks like?
It is what dichromacy — a completely missing cone class — projects to, which is the severe end. Most people with a deficiency are anomalous trichromats: the cone is there with a shifted response, and their experience sits between this and yours.
What does the severity slider do?
It blends linearly towards the dichromat result. That is not the Machado et al. (2009) model, which fits a separate matrix per severity step — at severity 1 the two agree by construction, and in between this is an approximation, labelled as one on the page.
A low figure means my chart is fine?
It means little colour moved on average, which a mostly-white page achieves trivially. Look at the simulated image too: two series that were red and green can collide while the average barely shifts.
Feed it from
Brightness & Colour Adjust
Adjusts brightness, contrast, saturation, temperature and sharpness with a live histogram.
Contrast Checker
Scores a foreground and background pair against WCAG 2 and APCA and suggests the nearest passing colour.
PNG Compressor
Quantises the palette and rewrites the deflate stream to shrink a PNG without changing its dimensions.
JPEG Compressor
Re-encodes a JPEG at a chosen quality with a live before/after size and a difference view.
Next
These accept what this tool produces, so the result can go straight in.
Contrast Checker
Scores a foreground and background pair against WCAG 2 and APCA and suggests the nearest passing colour.
Palette Extractor
Pulls an N-colour palette out of an image and exports it as hex, CSS variables or an ASE swatch.
Palette Generator
Builds a harmonious palette from a base colour using complementary, triadic and analogous rules.
Background Remover
Keys out a flat or single-colour background in OKLab and returns a transparent PNG, with a brush for fixing the edges.
EXIF Remover
Strips camera, GPS and editing metadata from photos while leaving the pixels untouched.
Favicon Generator
Produces the whole favicon set — ICO, PNGs, Apple touch icon, web manifest — plus the HTML to paste.