Color Picker
Pick and convert colors.
OpenCheck WCAG contrast. - runs entirely in your browser. Free, fast and private.
Set text color hex for the element under test.
Set the surface color behind the text.
WCAG 2.1 ratio calculates from relative luminance.
See whether normal and large text meet accessibility levels.
Contrast Checker is a free colour utility on OneDevToolkit. Check WCAG contrast. It runs in your browser for this session - use the workspace on this page to try it.
Need a related step? Open the Colour Tools hub at /color-tools/ or the <a href="/blog/">blog</a> for longer workflows.
Processes data instantly with no server round-trips.
Your data never leaves your browser. Nothing is uploaded.
Works in any modern browser. Nothing to download or install.
No limits, no sign-up, no credit card required.
Works on desktop, tablet and mobile devices.
Beautiful in both themes. Your preference is saved.
Keyboard shortcut
Open Contrast Checker when you need a quick result without uploading data to a third-party site.
No install required - bookmark the tool and return anytime.
Client-side processing keeps inputs on your device for core OneDevToolkit tools.
Answers for this tool. For site-wide help, open the FAQ hub.
Image tools process pixels in the browser with Canvas and related APIs. Images are not uploaded to OneDevToolkit for these client-side jobs.
PNG, JPEG, and WebP are widely supported. Some tools also accept GIF or SVG depending on the operation.
Lossless operations keep quality; JPEG/WebP compression trades quality for size. Use higher quality settings when print fidelity matters.
Yes for tools that preserve alpha. Converting to JPEG removes transparency - keep PNG/WebP when you need an alpha channel.
Limits come from browser memory. Extremely large megapixel images may fail - downscale first if needed.
Many image studios show preview panels. Download both versions if you need an external comparison.
Some tools intentionally remove EXIF; others preserve pixels only. Check the tool description for metadata behaviour.
If the UI shows a multi-file queue, yes. Otherwise process files one by one or script downloads locally after each run.
HEIC from some phones may need conversion to JPEG/PNG first. Export from Photos as JPEG when uploads fail.
Browse Colour Tools for resize, convert, compress, and EXIF utilities that match Contrast Checker.