Free Coblis Alternative
Coblis (Color Blindness Simulator) from Colblindor is one of the most well-known color vision deficiency simulators on the web. It transforms any uploaded image to show how it appears under various types of color blindness, including Protanopia, Deuteranopia, and Tritanopia. Coblis uses client-side JavaScript for image processing (based on the jsColorblindSimulator project), which means your images are processed locally in your browser. While Coblis is free and doesn't require an account, Fixie's Color Blind Simulator offers additional comparison modes and a cleaner interface focused purely on accessibility testing.
Try Color Blind Simulator Free →Color Blind Simulator vs Coblis
| Feature | Fixie Color Blind Simulator | Coblis |
|---|---|---|
| Price | Free forever | Free |
| Signup Required | No | No |
| Processing Location | 100% client-side (browser) | Client-side (browser) |
| CVD Types Supported | 7 types (Protanopia, Deuteranopia, Tritanopia + anomalies + Achromatopsia) | Multiple types including main deficiencies |
| Side-by-Side Comparison | Before/after slider + grid view | Sequential view |
| Color Picker Mode | Yes (test colors directly) | Image only |
| Download Simulations | Download individual or all at once | Download processed image |
| Ads | None | None |
Why Choose Fixie?
Coblis has been a trusted tool for designers and developers for years. It's built on solid scientific foundations (using jsColorblindSimulator by MaPePeR) and processes everything client-side, which means your images never leave your browser. The tool is simple to use: upload an image, choose a color blindness type, and see the result. Coblis also includes pan and zoom features, making it easy to inspect details in larger images.
However, Coblis shows each simulation type one at a time. If you want to compare multiple CVD types side-by-side, you need to generate each one separately and manually compare them. This sequential workflow can be slower when you're testing accessibility across multiple deficiency types, which is a common requirement in design work.
Fixie's Color Blind Simulator builds on the same scientific principles but adds comparison-focused workflows. The before/after slider lets you drag to compare normal vision against any CVD type instantly. The grid view shows all seven deficiency types at once, making it easy to spot which colors might be problematic across the full spectrum of color vision differences. You can also test individual colors without uploading an image, which is useful when choosing palettes or verifying color contrast ratios. Both tools are free, client-side, and privacy-respecting — Fixie just optimizes for faster multi-type comparison.
How to Use Color Blind Simulator
Step 1: Open the Color Blind Simulator
Visit fixie.tools/color-blind — no account or signup needed. Works on any device with a modern browser.
Step 2: Upload an Image or Pick Colors
You can either upload an image (JPG, PNG, WebP) or use the color picker to test specific colors. Images are processed entirely in your browser — nothing is uploaded to a server.
Step 3: Choose a Comparison Mode
Select the before/after slider mode to compare normal vision against a specific CVD type (Protanopia, Deuteranopia, Tritanopia, or the partial variants). Or choose the grid view to see all seven deficiency types displayed at once.
Step 4: Download Results
Download individual simulations or click "Download all" to get every CVD type as separate files. Perfect for accessibility documentation or client presentations.