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ImageZap

Resize images

Shrink the dimensions of many images at once with a high-quality filter and, if you like, convert them to a modern format in the same step.

Drop your images here

or paste with Ctrl+V · JPG, PNG, WebP, AVIF, JXL, GIF, HEIC · up to 30 MB each

Images are processed on your device and stored only in this browser so you can convert them again.

The setting that saves the most

Before thinking about formats or quality, check the dimensions. A phone photo is about 4000 × 3000 pixels; if your site displays it 1200 px wide, the browser downloads more than 10 times the pixels it needs. Resizing to the real display size usually saves more than any other setting.

Resize modes

  • Max width: every image wider than the value is shrunk, keeping its aspect ratio. The most common choice for websites and blogs.
  • Max height: useful for galleries or thumbnail strips with a fixed height.
  • Fit in box: the image fits inside a rectangle (for example 1920 × 1080) without being cropped.
  • Percentage: scales everything by the same factor, for example 50% to go from @2x to @1x.

Images are never upscaled: if one is already smaller than the limit, it stays as is.

Resizing quality

ImageZap uses the Lanczos3 filter in linear color space with premultiplied alpha. In practice:

  • Fine details stay sharp without the jagged look of fast methods.
  • Gradients and colors don't darken when shrinking (a typical problem when resizing in sRGB).
  • Edges of transparent images don't develop dark halos.

Variants for srcset

If you're preparing images for a responsive site, turn on Responsive variants and pick the widths (for example 640, 1280 and 1920). You'll get one file per width and format, and the code generator will write the matching srcset and sizes. More details in the responsive images guide.

Which size to choose

UseRecommended width
Full-screen image (hero)1920–2560 px
In-article content image1200–1600 px
Cards and listings640–800 px
Thumbnails320–400 px

For high-density screens, combine max width with responsive variants instead of always serving the largest version.

Frequently asked questions

Is the aspect ratio preserved?

Yes, in every mode. ImageZap never distorts or crops images.

Can I resize and convert at the same time?

Yes. Choose the output format (WebP, AVIF…) along with the size; by default the original format is kept.

How many images can I resize?

As many as you like, up to 30 MB each.

Can I enlarge a small image?

No. Upscaling adds no detail and only increases file size, which is why ImageZap never scales above the original size.

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