Transform via URL

You can convert and resize images by requesting them via a specially-formatted URL. This way you do not need to write any code, only change HTML markup of your website to use the new URLs. The format is:

https://<ZONE>/cdn-cgi/image/<OPTIONS>/<SOURCE-IMAGE>

Here is a breakdown of each part of the URL:

• <ZONE>

  • Your domain name on Cloudflare. Unlike other third-party image resizing services, image transformations do not use a separate domain name for an API. Every Cloudflare zone with image transformations enabled can handle resizing itself. In URLs used on your website this part can be omitted, so that URLs start with /cdn-cgi/image/.

• /cdn-cgi/image/

  • A fixed prefix that identifies that this is a special path handled by Cloudflare’s built-in Worker.

• <OPTIONS>

  • A comma-separated list of options such as width, height, and quality.

• <SOURCE-IMAGE>

  • An absolute path on the origin server, or an absolute URL (starting with https:// or http://), pointing to an image to resize. The path is not URL-encoded, so the resizing URL can be safely constructed by concatenating /cdn-cgi/image/options and the original image URL. For example: /cdn-cgi/image/width=100/https://s3.example.com/bucket/image.png.

Here is an example of an URL with <OPTIONS> set to width=80,quality=75 and a <SOURCE-IMAGE> of uploads/avatar1.jpg:

<img src="/cdn-cgi/image/width=80,quality=75/uploads/avatar1.jpg" />

Note

You can use image transformations to sanitize SVGs, but not to resize them. Refer to Resize with Workers for more information.

Options

You must specify at least one option. Options are comma-separated (spaces are not allowed anywhere). Names of options can be specified in full or abbreviated.

anim

Whether to preserve animation frames from input files. Default is true. Setting it to false reduces animations to still images. This setting is recommended when enlarging images or processing arbitrary user content, because large GIF animations can weigh tens or even hundreds of megabytes. It is also useful to set anim:false when using format:"json" to get the response quicker without the number of frames.

URL format

anim=false

Workers

cf: {image: {anim: false}}

background

Background color to add underneath the image. Applies to images with transparency (for example, PNG) and images resized with fit=pad. Accepts any CSS color using CSS4 modern syntax, such as rgb(255 255 0) and rgba(255 255 0 100).

URL format

background=%23RRGGBB

OR

background=red

Workers

cf: {image: {background: "#RRGGBB"}}

blur

Blur radius between 1 (slight blur) and 250 (maximum). Be aware that you cannot use this option to reliably obscure image content, because savvy users can modify an image’s URL and remove the blur option. Use Workers to control which options can be set.

URL format

blur=50

Workers

cf: {image: {blur: 50}}

border

Adds a border around the image. The border is added after resizing. Border width takes dpr into account, and can be specified either using a single width property, or individually for each side.

Workers

cf: {image: {border: {color: "rgb(0,0,0,0)", top: 5, right: 10, bottom: 5, left: 10}}}
cf: {image: {border: {color: "#FFFFFF", width: 10}}}

brightness

Increase brightness by a factor. A value of 1.0 equals no change, a value of 0.5 equals half brightness, and a value of 2.0 equals twice as bright. 0 is ignored.

URL format

brightness=0.5

Workers

cf: {image: {brightness: 0.5}}

compression

Slightly reduces latency on a cache miss by selecting a quickest-to-compress file format, at a cost of increased file size and lower image quality. It will usually override the format option and choose JPEG over WebP or AVIF. We do not recommend using this option, except in unusual circumstances like resizing uncacheable dynamically-generated images.

URL format

compression=fast

Workers

cf: {image: {compression: "fast"}}

contrast

Increase contrast by a factor. A value of 1.0 equals no change, a value of 0.5 equals low contrast, and a value of 2.0 equals high contrast. 0 is ignored.

URL format

contrast=0.5

Workers

cf: {image: {contrast: 0.5}}

dpr

Device Pixel Ratio. Default is 1. Multiplier for width/height that makes it easier to specify higher-DPI sizes in <img srcset>.

URL format

dpr=1

Workers

cf: {image: {dpr: 1}}

fit

Affects interpretation of width and height. All resizing modes preserve aspect ratio. Used as a string in Workers integration. Available modes are:

• scale down
  Similar to contain, but the image is never enlarged. If the image is larger than given width or height, it will be resized. Otherwise its original size will be kept. Example:

URL format

fit=scale-down

Workers

cf: {image: {fit: "scale-down"}}

• contain
  Image will be resized (shrunk or enlarged) to be as large as possible within the given width or height while preserving the aspect ratio. If you only provide a single dimension (for example, only width), the image will be shrunk or enlarged to exactly match that dimension.

URL format

fit=contain

Workers

cf: {image: {fit: "contain"}}

• cover
  Resizes (shrinks or enlarges) to fill the entire area of width and height. If the image has an aspect ratio different from the ratio of width and height, it will be cropped to fit.

URL format

fit=cover

Workers

cf: {image: {fit: "cover"}}

• crop
  Image will be shrunk and cropped to fit within the area specified by width and height. The image will not be enlarged. For images smaller than the given dimensions, it is the same as scale-down. For images larger than the given dimensions, it is the same as cover. See also trim

URL format

fit=crop

Workers

cf: {image: {fit: "crop"}}

• pad
  Resizes to the maximum size that fits within the given width and height, and then fills the remaining area with a background color (white by default). This mode is not recommended, since you can achieve the same effect more efficiently with the contain mode and the CSS object-fit: contain property.

URL format

fit=pad

Workers

cf: {image: {fit: "pad"}}

format

Note

At the moment, this setting only works directly with image transformations.

The auto option will serve the WebP or AVIF format to browsers that support it. If this option is not specified, a standard format like JPEG or PNG will be used. Cloudflare will default to JPEG when possible due to the large size of PNG files.

Workers integration supports:

• avif: Generate images in AVIF format if possible (with WebP as a fallback).
• webp: Generate images in Google WebP format. Set the quality to 100 to get the WebP lossless format.
• jpeg: Generate images in interlaced progressive JPEG format, in which data is compressed in multiple passes of progressively higher detail.
• baseline-jpeg: Generate images in baseline sequential JPEG format. It should be used in cases when target devices don’t support progressive JPEG or other modern file formats.
• json: Instead of generating an image, outputs information about the image in JSON format. The JSON object will contain data such as image size (before and after resizing), source image’s MIME type, and file size.

URL format

format=auto

URL format alias

f=auto

Workers

cf: {image: {format: "avif"}}

For the format:auto option to work with a custom Worker, you need to parse the Accept header. Refer to this example Worker for a complete overview of how to set up an image transformation Worker.

Custom Worker for Image Resizing with format:auto

const accept = request.headers.get("accept");
let image = {};

if (/image\/avif/.test(accept)) {
    image.format = "avif";
} else if (/image\/webp/.test(accept)) {
    image.format = "webp";
}

return fetch(url, {cf:{image}});

gamma

Increase exposure by a factor. A value of 1.0 equals no change, a value of 0.5 darkens the image, and a value of 2.0 lightens the image. 0 is ignored.

URL format

gamma=0.5

Workers

cf: {image: {gamma: 0.5}}

gravity

When cropping with fit: "cover" and fit: "crop", this parameter defines the side or point that should not be cropped. Available options are:

• auto
  Selects focal point based on saliency detection (using maximum symmetric surround algorithm).

URL format

gravity=auto

URL format alias

g=auto

Workers

cf: {image: {gravity: "auto"}}

• side
  A side ("left", "right", "top", "bottom") or coordinates specified on a scale from 0.0 (top or left) to 1.0 (bottom or right), 0.5 being the center. The X and Y coordinates are separated by lowercase x in the URL format. For example, 0x1 means left and bottom, 0.5x0.5 is the center, 0.5x0.33 is a point in the top third of the image.

  For the Workers integration, use an object {x, y} to specify coordinates. It contains focal point coordinates in the original image expressed as fractions ranging from 0.0 (top or left) to 1.0 (bottom or right), with 0.5 being the center. {fit: "cover", gravity: {x:0.5, y:0.2}} will crop each side to preserve as much as possible around a point at 20% of the height of the source image.

Note

You must subtract the height of the image before you calculate the focal point.

URL format

gravity=left

or

gravity=0x1

Workers

cf: {image: {gravity: "right"}}

or

cf: {image: {gravity: {x:0.5, y:0.2}}}

height

Specifies maximum height of the image in pixels. Exact behavior depends on the fit mode (described below).

URL format

height=250

URL format alias

h=250

Workers

cf: {image: {height: 250}}

metadata

Controls amount of invisible metadata (EXIF data) that should be preserved. Color profiles and EXIF rotation are applied to the image even if the metadata is discarded. Note that if the Polish feature is enabled, all metadata may have been removed already and this option will have no effect.

Note

Even when choosing to keep EXIF metadata, Cloudflare will modify JFIF data (potentially invalidating it) to avoid the known incompatibility between the two standards. For more details, refer to JFIF Compatibility ↗.

Options include:

• keep
  Preserves most of EXIF metadata, including GPS location if present.

URL format

metadata=keep

Workers

cf: {image: {metadata: "keep"}}

• copyright
  Discard all metadata except EXIF copyright tag. This is the default behavior for JPEG images.

URL format

metadata=copyright

Workers

cf: {image: {metadata: "copyright"}}

• none
  Discard all invisible EXIF metadata. Currently, WebP and PNG output formats always discard metadata.

URL format

metadata=none

Workers

cf: {image: {metadata: "none"}}

onerror

Note

At the moment, this setting only works directly with image transformations and does not support resizing with Cloudflare Workers.

In case of a fatal error that prevents the image from being resized, redirects to the unresized source image URL. This may be useful in case some images require user authentication and cannot be fetched anonymously via Worker. This option should not be used if there is a chance the source image is very large. This option is ignored if the image is from another domain, but you can use it with subdomains.

URL format

onerror=redirect

quality

Note

At the moment, this setting only works directly with image transformations.

Specifies quality for images in JPEG, WebP, and AVIF formats. The quality is in a 1-100 scale, but useful values are between 50 (low quality, small file size) and 90 (high quality, large file size). 85 is the default. When using the PNG format, an explicit quality setting allows use of PNG8 (palette) variant of the format.

URL format

quality=50

URL format alias

q=50

Workers

cf: {image: {quality: 50}}

rotate

Number of degrees (90, 180, or 270) to rotate the image by. width and height options refer to axes after rotation.

URL format

rotate=90

Workers

cf: {image: {rotate: 90}}

sharpen

Specifies strength of sharpening filter to apply to the image. The value is a floating-point number between 0 (no sharpening, default) and 10 (maximum). 1 is a recommended value for downscaled images.

URL format

sharpen=2

Workers

cf: {image: {sharpen: 2}}

trim

Specifies a number of pixels to cut off on each side. Allows removal of borders or cutting out a specific fragment of an image. Trimming is performed before resizing or rotation. Takes dpr into account. For image transformations and Cloudflare Images, use as four numbers in pixels separated by a semicolon, in the form of top;right;bottom;left or via separate values trim.width,trim.height, trim.left,trim.top. For the Workers integration, specify an object with properties: {top, right, bottom, left, width, height}.

URL format

trim=20;30;20;0
trim.width=678
trim.height=678
trim.left=30
trim.top=40

Workers

cf: {image: {trim: {top: 12,  right: 78, bottom: 34, left: 56, width:678, height:678}}}

width

Specifies maximum width of the image in pixels. Exact behavior depends on the fit mode (described below).

URL format

width=250

URL format alias

w=250

Workers

cf: {image: {width: 250}}

Recommended image sizes

Ideally, image sizes should match exactly the size they are displayed on the page. If the page contains thumbnails with markup such as <img width="200" …>, then images should be resized to width=200. If the exact size is not known ahead of time, use the responsive images technique.

If you cannot use the <img srcset> markup, and have to hardcode specific maximum sizes, Cloudflare recommends the following sizes:

• Maximum of 1920 pixels for desktop browsers.
• Maximum of 960 pixels for tablets.
• Maximum of 640 pixels for mobile phones.

Here is an example of markup to configure a maximum size for your image:

/cdn-cgi/image/fit=scale-down,width=1920/<YOUR-IMAGE>

The fit=scale-down option ensures that the image will not be enlarged unnecessarily.

You can detect device type by enabling the CF-Device-Type header via Cache Rule.

Caching

Resizing causes the original image to be fetched from the origin server and cached — following the usual rules of HTTP caching, Cache-Control header, etc.. Requests for multiple different image sizes are likely to reuse the cached original image, without causing extra transfers from the origin server.

Note

If Custom Cache Keys are used for the origin image, the origin image might not be cached and might result in more calls to the origin.

Resized images follow the same caching rules as the original image they were resized from, except the minimum cache time is one hour. If you need images to be updated more frequently, add must-revalidate to the Cache-Control header. Resizing supports cache revalidation, so we recommend serving images with the Etag header. Refer to the Cache docs for more information.

Cloudflare Images does not support purging resized variants individually. URLs starting with /cdn-cgi/ cannot be purged. However, purging of the original image’s URL will also purge all of its resized variants.