Make image thumbnails — small previews at an exact size

How to use Image Thumbnail

1. Choose one or more images (JPEG, PNG, WebP, GIF, AVIF, BMP or TIFF).
2. Enter the Size in pixels, from 8 to 4,000. It starts at 300.
3. Under Shape, pick Keep proportions or Square (crop to fill).
4. Leave Save as on JPEG, or choose PNG, WebP or Same format as the original. Set Quality for JPEG and WebP (90% by default).
5. Press Make thumbnails and download the files ending in -thumb.

What it does and when to use it

A thumbnail is a small copy of a picture used where space is tight: a product grid in an online shop, a gallery index, a blog’s “related posts” box, a contact photo or a preview inside a document. Making them ahead of time means a page loads a 20 KB picture instead of a 4 MB original.

Choose Keep proportions when the whole picture must stay visible, such as a screenshot or a document scan. Choose Square for grids, where tiles of the same shape look tidy. For other sizes, such as exactly 1200 px wide, the Image Resizer gives full control. For a round avatar, try the Circle Crop tool.

How it works

Each file is decoded inside a Web Worker in your browser, with any phone orientation tag applied first. With Keep proportions the scale factor is the size divided by the longer side, and it is never above 1. With Square, the tool cuts the largest centred square out of the picture and then scales it to the size.

Shrinking uses a filter that averages all the source pixels behind each new pixel, so fine patterns blend smoothly instead of flickering. The result is then saved by the browser’s own encoder. Nothing is uploaded.

Worked examples

These sizes follow from the tool’s own formulas.

A camera photo for a shop grid. A 4000 × 3000 px JPEG with Size 300 and Keep proportions becomes 300 × 225 px. The same photo held upright (3000 × 4000) becomes 225 × 300 px.

Square tiles. Size 150 with Square (crop to fill): from 4000 × 3000 px the tool keeps the centre 3000 × 3000 px (cutting 500 px from each side) and scales it to 150 × 150 px.

An image that is already small. A 200 × 100 px icon with Size 300 and Keep proportions stays 200 × 100 px, because the tool does not enlarge.

Limits and tips

• Metadata is not copied. Camera details and GPS position are not carried into the thumbnail.
• Animated GIFs become a single still frame.
• Need a file under a size limit? Run the thumbnail through Compress Image to 100 KB or a smaller target.
• Want to embed a tiny icon straight into HTML or CSS? Turn the thumbnail into a data URI with Image to Base64.