The best website image size is not one universal width or file-weight target. It depends on how large the image appears, the visitor's screen density, the layout and the content inside the picture. A useful workflow separates dimensions, aspect ratio, file format and compression.
Pixel dimensions: match the display area
Dimensions are the width and height in pixels. An image displayed in a 600-pixel-wide content column rarely needs to be several thousand pixels wide. Supplying an image close to the largest rendered size avoids transferring pixels that most visitors never see.
Allow for high-density screens
A common practical approach is to provide a source around twice the CSS display width when very sharp presentation matters. For example, a 600-pixel-wide display slot may use a 1200-pixel-wide source. Responsive image markup can let the browser choose a smaller source for smaller screens.
Aspect ratio controls the shape
Width and height together create the image ratio. A 1200 × 800 photo is 3:2; a 1200 × 675 hero image is 16:9. Use the Aspect Ratio Calculator when you know one side, or the Image Dimensions Checker to identify an existing file.
File size affects loading
Two images can have identical dimensions but different file sizes. Photographic detail, format, metadata and compression all matter. Resize oversized originals first, choose an appropriate format, then compress while checking the actual page for visible damage.
Choose a format by content
- JPEG/JPG: broadly supported and effective for photographs without transparency.
- PNG: useful for transparency and graphics that need lossless detail, but can be large for photos.
- WebP: often provides smaller web files while supporting photos and transparency.
- SVG: ideal for suitable vector logos and icons; do not use it for ordinary photographs.
Example starting points
| Use | Example source width | What to check |
|---|---|---|
| Article image | 1200–1600 px | Actual content-column width |
| Full-width hero | 1600–2400 px | Largest layout and crop behavior |
| Card thumbnail | 600–1000 px | Repeated loading and consistent ratio |
| Logo | SVG when suitable | Transparency and clear space |
These are starting points, not platform requirements. Measure the real layout and test it.
A practical optimization sequence
- Decide where the image appears and its largest displayed dimensions.
- Choose the crop and ratio before resizing.
- Use Resize Image to reduce oversized files.
- Export in a suitable format and use Compress Image if needed.
- Check clarity, layout shifts and loading on both mobile and desktop.