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║ your eyes, tested in the browser, with nothing leaving it ║
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An open, published method for color vision — and 17 vision tests built on it.
Everything runs on the device. No account, no upload, no image ever sent anywhere.
The colorimetry is not a private formula: it is Machado, Oliveira & Fernandes (2009)
deficiency simulation with CIEDE2000 color difference, published open access at
doi.org/10.5281/zenodo.21310578, and shipped as
packages so you can run the math yourself and check our numbers against yours.
Use the engine
pip install cvdsafe
npm install cvdsafe
import cvdsafe
cvdsafe.is_safe(["#d7191c", "#1a9641"])
npx cvdsafe "#d7191c" "#1a9641"
| what you want | package |
|---|
| Is this palette safe? | cvdsafe · npm + PyPI, with a CLI |
| Show me how it looks | cvdsim — recolors an image for protan/deutan/tritan |
| Give me safe colors | safepalette — Okabe–Ito, extended and verified |
| For matplotlib | cvdmaps — set_cycle() and you're safe |
| Make test plates | cvdplate · ishihara |
| Acuity math | logmar — logMAR ↔ Snellen ↔ decimal |
| One deficiency | protan · deutan · tritanopia · dichromacy · achromatopsia · trichromacy |
For LLM tools: cvdsafe-mcp and colorblind-mcp are MCP servers, listed in the official
Model Context Protocol registry — so an assistant can check a palette or generate an Ishihara
plate as a native tool.
The tests
Color vision, D-15 arrangement, hue discrimination, anomaloscope-style matching, contrast
sensitivity, acuity, astigmatism, Amsler grid, blind spot, vernier alignment, flicker fusion,
saturation, dominance, reaction, stereo depth, digital eye strain, and a shape-based test for
kids.
A test on a web page cannot be a diagnosis: an uncalibrated display, ambient light and viewing
distance all move the result. Each test says so where it reports, and points at an eye
examination rather than standing in for one.
Audit it yourself. opticquiz.com/methodology answers the
eight questions worth asking of any online vision test — who made it, what it measures, what it
assumes about your screen, whether it has been clinically validated (it has not), what it cannot
measure, and who pays for it.
Also in here
Translations (de, es, fr, hi, it, pt, zh), a browser extension (reviewed and listed by Mozilla),
a VS Code extension, a Figma plugin, an embeddable widget, and the research notes behind the
plate colors under research/.
MIT licensed. Issues and corrections welcome — if a number here disagrees with yours, that is a
bug worth reporting.
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║ ╚═╝ ╚═╝ ╚═╝╚══════╝ ╚═╝ ╚══════╝ ║
║ ║
║ · C R E A T I V E · ║
║ ║
║ ──────────────────────────────────────── ║
║ ║
║ Vincent Gonzalez ║
║ f-keys.com ║
║ ORCID 0009-0005-3640-014X ║
║ ║
╚════════════════════════════════════════════════════════════╝
Part of F-Keys — independent hardware, software
and internet products. See the working log
and live status.