How to Reduce Image File Size for a Website
Large images can slow down page loading and use more bandwidth than necessary. With suitable dimensions, formats, and compression settings, you can reduce image file sizes while keeping your images clear.
A practical guide to optimizing website images.
1. Resize images to suitable dimensions
An image may contain far more pixels than a page needs. For example, uploading a 4000-pixel-wide photograph for a content area that displays it at around 800 pixels wide may add unnecessary file size.
Check the intended display size before resizing. High-density screens may benefit from images with more pixels than their displayed CSS width, so avoid shrinking every image to the smallest possible dimensions.
Use the MARBPixel Image Resizer to set custom pixel dimensions or resize an image by percentage. Preserve the aspect ratio to avoid stretching or squashing the image.
2. Choose the right image format
Different formats suit different kinds of images. Choosing an appropriate format can reduce file size while preserving the details that matter.
| Format | Useful for | Things to know |
|---|---|---|
| WebP | Many photographs, graphics, and website images | Often provides a good balance of quality and file size. |
| JPEG / JPG | Photographs and complex images | Lossy compression can reduce file size substantially. |
| PNG | Images that need transparency or crisp-edged graphics | Can be larger than JPEG or WebP for photographic content. |
There is no single best format for every image. Consider transparency, compatibility, visual detail, and your website's requirements. Read our guide to JPG vs PNG vs WebP for a more detailed comparison.
3. Compress the image carefully
Compression reduces the amount of data needed to store an image. Lossy compression can save considerable space, but aggressive settings may introduce visible artifacts, blur, or banding.
- Keep a copy of the original image.
- Choose a suitable output format.
- Start with a moderate compression or quality setting.
- Preview the image at its intended display size.
- Compare the visual result and file size with the original.
Try the MARBPixel Image Compressor to adjust image quality and compress supported images directly in your browser. The best setting depends on the image and how much detail you need to retain.
4. Balance file size and visual quality
The smallest possible file is not always the best result. If compression makes a photograph look blocky or makes text in a graphic difficult to read, the savings may not be worthwhile.
Inspect important details, edges, gradients, and text. Compare images at approximately the size visitors will see them. Zooming in can reveal artifacts, while viewing a tiny preview can hide problems.
5. Optimize images for their purpose
Different images on the same website may need different settings. A large banner photograph, a small thumbnail, and a transparent logo do not necessarily benefit from the same format or compression level.
Choose settings based on how the image will be used. Prioritize clear details for important graphics and text, and avoid keeping unnecessary pixel dimensions for small decorative images.
6. Keep the original file
Save an original copy before resizing or applying lossy compression. If you later need a larger version or a different format, you can start again from the original rather than repeatedly compressing an already degraded image.
Website image optimization checklist
- Use dimensions appropriate for the image's display size.
- Choose a format that suits the image and its transparency needs.
- Compress with sensible quality settings.
- Preview the result before publishing it.
- Keep a copy of the original image.
- Compare file size and visual quality together.
Try our free image tools
Compress, resize, or convert supported images with MARBPixel's online tools.
Frequently asked questions
How can I reduce image file size for a website?
Resize the image to suitable dimensions, choose a format such as WebP or JPEG, and apply compression while checking the visual result.
Which image format is best for websites?
WebP is useful for many website images. JPEG works well for photographs, while PNG is useful when transparency or specific graphic details are needed.
Does image compression reduce quality?
Lossy compression can reduce visual quality, particularly at aggressive settings. Preview the compressed image and compare it with the original.
Should I resize an image before compressing it?
If an image is much larger than its intended display size, resizing it first can reduce unnecessary data. You can then choose a suitable format and compression setting.