Contrast Checker
WCAG contrast ratio for any text and background pair.
Normal text needs 4.5:1
Large heading sample
Body copy at 16px, the size most guidelines judge first.
Small print at 12.8px needs the same 4.5:1 threshold.
How to Use Contrast Checker
Select or Upload
Choose your file or paste your input into the workspace above. Drag and drop is supported.
Configure & Process
Adjust options to fit your task. Processing runs immediately with no waiting queue.
Download Result
Preview and save your output in one click with no watermarks or sign-up prompts.
Private & Confidential
Browser tools process files locally on your device, and server temporary files are deleted automatically within 15 minutes.
Free & No Registration
Full access to every utility without creating an account, signing in, or hitting paywalls.
Works on Any Device
Responsive layout that runs smoothly on desktop, tablet, and mobile browsers across all operating systems.
Frequently Asked Questions
Is Contrast Checker completely free to use?
Yes, Contrast Checker on KiloToolbox is 100% free with no limits, hidden fees, or account sign-up required.
Are my files safe and private?
Yes. Contrast Checker processes all files directly inside your web browser using client-side JavaScript and WebAssembly. Your files never leave your computer or mobile device and are never uploaded to any remote server.
Can I use Contrast Checker on mobile phones and tablets?
Yes, KiloToolbox is fully responsive and runs smoothly on iPhone, Android, iPad, Mac, Windows, and Linux.