GitHub README images display at the repository content width, which is approximately 700-800 pixels on desktop. Images wider than this are automatically scaled down by GitHub. Uploading at 800px wide ensures sharp display without unnecessary file size.
For screenshots in documentation, 800px wide provides good detail. For badges and small icons, keep dimensions under 200px. For hero images or project banners, 1280x640 works well for the 2:1 aspect ratio commonly used in GitHub social preview cards.
GitHub social preview images (shown when links are shared) should be 1280x640 pixels. Set this in your repository Settings under Social preview.
With ImgTools, resize documentation images to 800px wide and compress to keep the repository size manageable. Save screenshots as PNG for text clarity and photographs as JPEG.
All processing happens locally in your browser.