Thumbnail images are essential for image galleries, product grids, search results, and content previews. Common thumbnail sizes include 150x150 for small grids, 300x300 for medium thumbnails, 100x100 for compact lists, and 200x200 for profile-sized thumbnails.
The key to good thumbnails is ensuring the most important part of the image is visible at the small size. Center the subject, crop tightly, and avoid images with important details at the edges.
With ImgTools, upload your image, crop to a 1:1 square using the Crop tab (most thumbnails are square), then resize to your target dimension (150x150, 300x300, etc.) in the Resize tab.
Save thumbnails as JPEG at 75-80% quality. At these small dimensions, the file size is naturally tiny (5-20KB), so you do not need aggressive compression.
For web performance, serving properly sized thumbnails instead of full-size images that are scaled down by CSS can dramatically reduce page load time.
All processing happens locally in your browser.