Choose a font that is easy to read, even when the thumbnail is shown on small mobile devices. Your main topic should stand out visually and should not exceed 2 words. Use a bigger font size for the main topic than for other text. Ideally, this font size should be 120px or bigger. Secondary text should not be smaller than 75px. Avoid using more than two different fonts, as too many can make the thumbnail look cluttered. Make sure the font is legible on both light and dark backgrounds.
Use a simple and visually appealing background that complements the content of the video. Avoid using busy or distracting backgrounds that can make the thumbnail look cluttered. You can also use a solid color or a gradient as a background.
Consider using a contrasting color to the color that is typically used for videos that show up for this topic in YouTube search results. This can help your thumbnail stand out and may result in higher click-through-rates.
Use of Faces
Including a face in your thumbnail can help grab viewers' attention and make the video more relatable. However, make sure the face is relevant to the content of the video and not just a random image. Use a high-quality image and make sure the facial expression matches the tone of the video.
If you decide to include a face in your thumbnail, make sure it's at least 50% of the height of the thumbnail. This means the face should be between 320px to 540px in height.
Remember, your thumbnail is often the first thing viewers see when browsing YouTube, so make sure it accurately represents the content of your video and stands out from the crowd.
YouTube recommends the dimensions 1280x720 px. Other dimensions may cause black bars top/bottom or left-right on certain screen resolutions.