What contrast ratios do you check?

We compute WCAG 2.1 contrast ratio between your text color and the average background inside the selected area. We show AA/AAA thresholds for normal (4.5:1 / 7:1) and large text (3:1 / 4.5:1).

How accurate is the background sampling?

We sample the pixels inside your selection on the uploaded image. For patterned backgrounds, manual checks in multiple areas are recommended.

Does this upload my image?

No. Everything runs in your browser. Images are not sent to a server.

Tips for readable thumbnails?

Use large, bold fonts and high contrast (≥3:1 for large text). Add a subtle stroke or shadow to increase contrast on busy backgrounds.

Thumbnail Contrast Checker

Check contrast and text readability of thumbnails.

Tip: Your data stays in your browser.

Thumbnail image

Max ~10 MB. Your image stays in your browser.

Text color

Safe area Grid

Text areas

Preview

Results

B1: 0.00 : 1 — AA AAA AA Large AAA Large

FAQs

What contrast ratios do you check?
We compute WCAG 2.1 contrast ratio between your text color and the average background inside the selected area. We show AA/AAA thresholds for normal (4.5:1 / 7:1) and large text (3:1 / 4.5:1).
How accurate is the background sampling?
We sample the pixels inside your selection on the uploaded image. For patterned backgrounds, manual checks in multiple areas are recommended.
Does this upload my image?
No. Everything runs in your browser. Images are not sent to a server.
Tips for readable thumbnails?
Use large, bold fonts and high contrast (≥3:1 for large text). Add a subtle stroke or shadow to increase contrast on busy backgrounds.

Guides

Safe Text Areas for Thumbnails (YouTube/Shorts)

Where to place text so it stays readable across devices. Includes conservative overlay guides.

Read →