# YouTube thumbnail checker & preview

> Free YouTube thumbnail checker: size, contrast and readability checks, then a preview in a mock YouTube feed. Your image stays in your browser.

Interactive version (needs a browser; the image never leaves it): https://vid0.in/tools/youtube-thumbnail-preview

## What it checks

- **Size:** 16:9; 3840×2160 recommended, 1280×720 still sharp, 640 px minimum width; up to 50 MB.
- **Instant score (0–100):** brightness, contrast, colour, clutter and readability at 168×94.
- **Feed preview:** home, search, up next and mobile, in light and dark.

- **What size should a YouTube thumbnail be?** 16:9. YouTube recommends 3840×2160; 1280×720 still looks sharp on most screens, and the minimum width is 640 pixels. Thumbnails uploaded from a computer can be up to 50 MB.
- **Is my image uploaded anywhere?** No. The checks and the feed preview run in your browser, and the image never leaves this tab.
- **What does the instant score measure?** Brightness, contrast, colour, clutter and how well it reads at small sizes, blended into a 0 to 100 score. It's a quick heuristic, not a prediction of clicks.
- **How do I compare two thumbnails?** Check each one here. Signed in, Vid0's thumbnail lab compares up to three variants side by side among real competing videos, with an AI critique. [See pricing](https://vid0.in/pricing).