Open Source · Runs in your browser · No server
CMYK Print
Simulator
Upload any image and instantly see how it will shift when converted to CMYK for print. Visualize dot gain, check total ink coverage, and catch out-of-gamut colors — before you send the file.
Image downsampled to 1500px for performance. Preview quality is not affected.
Drop your image here
or click to browse — JPG, PNG or WEBP · Max 5MB
Simulation
Checker
Warning
Toggles
Common Questions
Everything you need to know about this tool and CMYK color for print.
Is this tool accurate enough for professional print?
No, and it is designed to be honest about that. This tool uses simplified mathematical formulas — not ICC profiles like FOGRA39, SWOP, or GRACoL. For production work, always do a proper ICC soft proof in Photoshop, InDesign, or your RIP software before sending files to press. This tool helps you understand the concepts and catch obvious problems early.
Does my image get uploaded to a server?
No. Your image never leaves your device. All processing happens in your browser using JavaScript and Web Workers. There is no server, no database, and no way for us to see your files. This is an entirely client-side static tool hosted on GitHub Pages.
What is total ink coverage and why does it matter?
Total ink coverage (TAC) is the sum of all four CMYK channel values at a given pixel. 300% means C100 + M100 + Y100 + K0, or any other combination adding to 300. Most press types have an ink limit — typically 240-320% depending on paper — because excessive ink causes drying failures, smearing, and press damage. This tool flags pixels that exceed the safe limit for your chosen paper type.
What is dot gain and why does print always look darker?
When ink hits paper fibers, it physically spreads outward — the dots get bigger than intended. On a 50% midtone, dot gain might push that to 65-70%, making the result darker and muddier than the screen preview. This tool simulates dot gain using a non-linear sine curve (not a flat linear percentage), which correctly affects midtones most and leaves shadows and highlights relatively unchanged — matching real press behavior.
Why do some colors show a gamut warning?
The CMYK color space is smaller than your monitor's RGB space. Certain colors — neon greens, electric blues, vivid oranges — are simply outside what any CMYK press can reproduce. They will be shifted to the nearest printable color, losing vibrancy in the process. The gamut is especially restricted on newsprint. This is a simplified warning system — for precise gamut checking, use Photoshop's Proof Colors feature with a proper ICC profile loaded.
Want to understand the deeper concepts? Read the full print color guide →