How to compress images for the web
By Sure INSTANT team · Updated on Nov 11, 2026
Heavy images are a common reason a page feels slow. Most of the weight comes from two things: a picture larger than the space it is shown in, and a format that does not suit its content.
This guide covers both: choosing the format and the compression, and the web sizes SmartImage Pack prepares.
Which format suits which image
SmartImage Pack can keep each image's own format or convert the batch to JPEG, PNG or WebP.
| Format | Suits |
|---|---|
| JPEG | Photographs |
| PNG | Flat graphics and transparency |
| WebP | Smaller files for the same look in modern browsers |
Quality level or file-size limit
There are two ways to control compression. A quality level applies the same setting to every image, so the file sizes vary from one picture to the next.
A file-size limit in KB works the other way round: for each image the tool searches for the best quality that stays under the limit. The limit needs JPEG or WebP as the output format.
The web sizes SmartImage Pack prepares
A picture saved at the size of its place on the page carries no pixels the visitor will never see.
| Name | Size in pixels |
|---|---|
| Full-width header | 1920×1080 |
| Wide banner | 1600×600 |
| Card image | 800×600 |
| Thumbnail | 400×400 |
| Icon | 512×512 |
Never enlarged beyond twice
Enlarging a small picture adds weight without adding detail. For this reason the tool never enlarges an image beyond twice its own size.
When the original is small, start from the largest version of the picture you have.
How to compress a batch with SmartImage Pack
- Upload up to 20 images in one go.
- Choose the web sizes you need, or type a custom size.
- Choose the output format: keep, JPEG, PNG or WebP.
- Set a quality level, or a file-size limit in KB with JPEG or WebP.
- Sign in to download the ZIP, then open its report to see each file's size and quality.