Contrast Checker · free online image tools tool
Check foreground/background contrast against WCAG. No install, opens instantly, works offline — data stays in your browser.
How to use Contrast Checker
- Open this page (or search “Contrast Checker” on www.258tool.com).
- Enter your input in the tool panel — results update instantly.
- Copy, download or save as needed; your data is stored locally on this device.
FAQ
Is Contrast Checker free?
Completely free. No sign-up, no account — open and use.
Is my data uploaded to a server?
No. All processing runs locally in your browser; data stays on your device.
Does Contrast Checker work offline?
Yes. After the first visit, add 258tool to your home screen and everything works offline.
ReferenceW3C WCAG 2.1《Web 内容无障碍指南》相对亮度与对比度公式 · https://www.w3.org/TR/WCAG21/#dfn-contrast-ratio