Caption Contrast Checker
Captions that vanish on a bright sky or a busy shot lose viewers on a phone screen. Upload one frame, choose your caption colour, stroke and box, then drag the caption to where the words will sit. This free checker samples the pixels underneath, reports the worst-case and median WCAG contrast, and tells you the smallest stroke or box opacity that passes. The frame never leaves your browser.
Captions, reframing and cuts done for you, with a story. Start with my footage
Free • No signup • Built by Market4Me.ai
How to use it
Upload a frame from the video where the captions appear.
Pick the caption colour, stroke and box, then drag the caption box to where the words will sit.
Read the worst-case ratio. Apply the suggested fix and check again until it passes.
Want this done for you?
This tool gives you the starting point. Market4Me writes, storyboards and makes the video, and shows the price before anything renders.
Make my first video →Frequently asked questions
What contrast ratio do captions need?
WCAG AA asks for 4.5:1 for normal text and 3:1 for large text. Captions are usually treated as normal text, so 4.5:1 is the safe target, measured against the darkest or brightest pixel under the caption.
Why check the worst case and not the average?
One unreadable patch is enough to lose words. The worst-case ratio shows the spot the text sits on that is hardest to read, while the median shows how the caption looks most of the time.
Does my frame get uploaded?
No. The frame is decoded and sampled in your browser. Nothing is sent to a server and no account is needed.