> ## Documentation Index
> Fetch the complete documentation index at: https://docs.bunny.net/llms.txt
> Use this file to discover all available pages before exploring further.
# Resizing
> Resize images by width or height while maintaining aspect ratio
Resize images to specific dimensions while automatically maintaining aspect ratio. Generate responsive images for different screen sizes, create consistent thumbnails, or optimize oversized images for faster loading.
When both width and height are specified, Bunny Optimizer automatically uses
whichever produces the smaller image while preserving aspect ratio.
## Parameters
Resize the image to match the given width in pixels while maintaining aspect
ratio.
**Unit:** pixels
Resize the image to match the given height in pixels while maintaining aspect
ratio.
**Unit:** pixels
Allows the image to be enlarged beyond its original dimensions.
**Values:** `off`, `resampling`
**Default:** `off`
The default upscaling behaviour can be changed to `resampling` (so you don't need to specify the query parameter each time)
in the Pull Zone config via the [Update Pull Zone](/api-reference/core/pull-zone/update-pull-zone) API by setting
`OptimizerEnableUpscaling` to `true`.
## How it works
When you apply width or height parameters, Bunny Optimizer:
1. Calculates the new dimensions based on your specified value
2. Maintains the original aspect ratio automatically
3. Resizes the image proportionally
4. Delivers the optimized result from the edge cache
## Usage
### Width-based resizing
Specify a width to resize the image proportionally. The height adjusts automatically to maintain aspect ratio. Ideal for creating responsive images where you need consistent widths across different screen sizes or generating multiple sizes for `srcset` attributes.
```bash theme={null}
https://yourzone.b-cdn.net/image.jpg?width=300
```
| Original | width=300 |
| ---------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------- |
|  |  |
```bash Smaller width theme={null}
https://yourzone.b-cdn.net/image.jpg?width=150
```
| Original | width=150 |
| ---------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------- |
|  |  |
### Height-based resizing
Specify a height to resize the image proportionally. The width adjusts automatically to maintain aspect ratio. Perfect for layouts where vertical space is constrained, such as horizontal carousels, fixed-height containers, or product listing grids.
```bash theme={null}
https://yourzone.b-cdn.net/image.jpg?height=150
```
| Original | height=150 |
| ---------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------ |
|  |  |
```bash Smaller height theme={null}
https://yourzone.b-cdn.net/image.jpg?height=100
```
| Original | height=100 |
| ---------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------ |
|  |  |
## Combining width and height
When both width and height are specified, Bunny Optimizer intelligently selects whichever produces the smaller image while preserving aspect ratio. This ensures images fit within specific layout constraints while maintaining their original proportions.
```bash theme={null}
https://yourzone.b-cdn.net/image.jpg?width=100&height=75
```
Given an image with dimensions 500×333:
| width=100 | height=75 | width=100\&height=75 (result) |
| ---------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------- |
|  |  |  |
In this example, `height=75` produces a smaller image (113×75) compared to `width=100` (100×67), so the height parameter takes effect.
## Combining with other transformations
Resizing works seamlessly with other Bunny Optimizer parameters. Reduce bandwidth by combining with quality adjustments, convert formats for better compression, or apply filters to enhance resized images:
```bash Resize with quality adjustment theme={null}
https://yourzone.b-cdn.net/image.jpg?width=800&quality=85
```
```bash Resize with format conversion theme={null}
https://yourzone.b-cdn.net/image.jpg?width=600&format=webp
```
```bash Resize with sharpen filter theme={null}
https://yourzone.b-cdn.net/image.jpg?height=400&sharpen=3
```
[Crop](/optimizer/dynamic-images/cropping) operations have priority over width
or height parameters. If any crop is defined in the query, it will be applied
first, then resizing is applied to the cropped result.
## Upscaling
By default, Bunny Optimizer does not enlarge images beyond their original size.
Use `upscaling=resampling` to permit standard resampling-based upscaling. When enabled, upscaling is limited to an output size of 24 megapixels while preserving aspect ratio.
This limit applies only when the result would be larger than the original image. If the original image is already larger than 24 megapixels, it is not reduced unless another transformation requires it.
```bash Upscale 1024x512 image to 2048x1024 theme={null}
https://yourzone.b-cdn.net/image.jpg?width=2048&upscaling=resampling
```
```bash Upscale 1024x512 image to 1536x768 theme={null}
https://yourzone.b-cdn.net/image.jpg?width=1536&height=768&upscaling=resampling
```
```bash Downscale 1024x512 image to 512x256. No upscaling (target is smaller than original). theme={null}
https://yourzone.b-cdn.net/image.jpg?width=512&upscaling=resampling
```