Possible Image Stack errors

A successfully converted image returns status 200, the converted content in the body, and the following response headers:

X-Img-Server
headers from origin
X-IMG-Saved-Bytes
X-IMG-Origin-Download-Time
X-IMG-Processing-Time
"Content-Type":"{image/webp or image/avif}"
Content-Length
X-GCDN-Origin-Size

Problems can occur when using Image Stack — an image may be delivered in its original state without processing, or may not appear on the page at all.

Check image details

Browser developer tools expose the status code, response headers, and body of each image request. 1. Navigate to the page containing the Image Stack images and open the developer tools (Ctrl+Shift+I for Chrome) 2. Navigate to the Network tab at the top 3. In the list of network requests on the left, click the image request to examine 4. Use the Headers tab to view the response headers and status code

How to check an image's details for troubleshooting

Identify the error by comparing the status code, response headers, and body output with the cases below.

Common errors that result in a broken image

These errors prevent the image from loading and return a non-200 HTTP status code.

Error	Details	Causes	Solutions
Incorrect image request method	Status: 405 Response Headers: X-GCDN-Img-Server Body: `"error": "method not found"`	The used request method is not GET	Use the GET request method
Incorrect format for conversion in headers or query	Status: 400 Response Headers: X-Img-Server Body: `"error": "only webp format supported"`	Image Stack is configured for WebP-only conversion and the request specifies AVIF or another unsupported format via the `fmt` parameter or `Accept` header	Set the format to WebP, or enable AVIF support in the Image Stack settings
Image Stack internal error	Status: 500 Response Headers: X-Img-Server Body: `"error": "<err>"`	Internal Image Stack error	Contact our technical support team at support@gcore.com
Origin timeout	Status: 504 Response Headers: X-Img-Server Body: `"error": "request to origin timeout: <err>"`	The origin did not respond	Fix outages at the origin
Too many requests to the origin	Status: 504 Response Headers: X-Img-Server Body: `"error": "too many requests"`	The origin is receiving too many requests	Reduce the number of requests to the origin with the paid Origin Shielding feature

Errors that return the original image

The request body is proxied from the origin. The response headers include X-Img-Server and headers from the origin. The status code is 200 OK.

Error	Details	Causes	Solutions
Unsupported content type from the origin for the converter	Response Header: `"IMG-SKIP-REASON":"detected content type <content type> is not supported"`	The image format is not supported	Change the image format to JPG or PNG
Quality difference skips for jpeg	Response Header: `"IMG-SKIP-REASON":"{webp/avif} will be bigger, than origin: OriginQ: <origin quality>, DesiredQ: <desired jpeg quality>"`	Compression occurred incorrectly; the quality of the processed image is greater than or equal to the original image	Verify that the original image is not already optimized — the official WebP guide explains when compression may increase file size
Invalid response code from the origin	Response Header: `"IMG-SKIP-REASON":"not valid response code from the origin; response code — {response code from client’s origin}"`	The origin responded to Image Stack with a non-200 response code and Image Stack could not retrieve the image	Verify that the origin responds with a 200 status code

Compression and quality operation errors

The request body is proxied from the origin. The response headers include X-Img-Server and headers from the origin. The status code is 200 OK.

Error	Details	Causes	Solutions
Rate limit exceeded	Response Header: `"IMG-SKIP-REASON":"compression: rate limit is exceeded"`	The rate limit for conversions to WebP and AVIF formats has been exceeded	Wait for the limit to renew, or request a limit increase by contacting support@gcore.com
Bad quality parameter	Response Header: `"IMG-SKIP-REASON":"compression: bad quality parameter"`	The quality parameter is invalid; we can’t convert the quality value to a number	Set the quality parameter to an integer between 1 and 100
Unsupported format of the fmt value	Response Header: `"IMG-SKIP-REASON":"compression: unsupported format of the fmt query parameter"`	The request attempted to convert an image to an unsupported format	Set WebP or AVIF as the fmt value according to the guide
The WebP or AVIF format is not supported by the user client	Response Header: `"IMG-SKIP-REASON":"compression: webp/avif format is not supported by the client"`	The WebP or AVIF format is not supported by the browser where the webpage is loaded	Select a browser that supports the required format
The output image size is bigger or equal to the original image size	Response Header: `"IMG-SKIP-REASON":"compression: output image size is bigger than/equal to the original image size"`	Image Stack skips compression when the output file size equals or exceeds the original — the original image is returned to prevent size increases	Reduce the `quality` value or change to a format that compresses more efficiently for this image type
Conversion to WebP or AVIF internal error	Response Header: `"IMG-SKIP-REASON":"compression: {image/webp or image/avif} conversion internal error"`	Internal conversion error	Contact our technical support team at support@gcore.com

Resize operation errors

The request body is proxied from the origin. The response headers include X-Img-Server and headers from the origin. The status code is 200 OK.

Error	Details	Causes	Solutions
Bad “width” parameter	Response Header: `"IMG-SKIP-REASON":"resizing: bad width parameter"`	The width parameter is invalid. We cannot parse the value to a number	Set a positive integer
Bad “height” parameter	Response Header: `"IMG-SKIP-REASON":"resizing: bad height parameter"`	The height parameter is invalid. We can’t parse value to a number	Set a positive integer
The output image width or height parameter is larger than the original image size	Response Header: `"IMG-SKIP-REASON":"resizing: destination image width or height parameter is more than the original image size"`	The request attempted to scale the image beyond its original size	Reduce the `width` and `height` parameter values to be smaller than the original image dimensions
Resizing internal error	Response Header: `"IMG-SKIP-REASON":"resizing: internal error"`	Internal Image Stack error	Contact our technical support team at support@gcore.com

Crop operation errors

The request body is proxied from the origin. The response headers include X-Img-Server and headers from the origin. The status code is 200 OK.

Error	Details	Causes	Solutions
Bad “width-ratio” or “height-ratio” parameter	Response Header: `"IMG-SKIP-REASON":"cropping: bad width-ratio or height-ratio parameter"`	The aspect ratio does not contain exactly two colon-separated values	Specify two values (numbers) using the ”:” delimiter
Bad “height ratio” parameter	Response Header: `"IMG-SKIP-REASON":"cropping: bad height ratio parameter"`	We can’t parse height value to an integer or value less than 0	Set the “height ratio” as a positive number according to the guide
Bad “width ratio” parameter	Response Header: `"IMG-SKIP-REASON":"cropping: bad width ratio parameter"`	We can’t parse width value to an integer or value less than 0	Set the “width ratio” as a positive number according to the guide
x or y parameter is not specified	Response Header: `"IMG-SKIP-REASON":"cropping: x or y parameter is not specified"`	The x or y parameters specifying the number of pixels to offset do not contain values	Specify x and y values
Bad x or/and y percentage parameter	Response Header: `"IMG-SKIP-REASON":"cropping: bad x/y percentage parameter"`	The x or y parameters cannot be parsed to an integer or have a value less than 0	Set the percentage between 0 and 100 [0, 100]
Bad x or y pixel parameter	Response Header: `"IMG-SKIP-REASON":"cropping: bad x/y pixels parameter"`	The x or y pixel parameters cannot be parsed to an integer or have a value less than 0	Set a positive integer for x and y
x and y pixels number parameter and percentage x and y parameter cannot be specified simultaneously	Response Header: `"IMG-SKIP-REASON":"cropping: x/y pixel and percentage values cannot be specified simultaneously"`	The x and y values are specified twice: once in pixels and once as a percentage	Use only one method to specify the x and y values
Bad offset value for the x or y parameter	Response Header: `"IMG-SKIP-REASON":"cropping: bad offset-x/y parameter"`	The value of offset for x or y is empty	Specify x and y values for offset; it should be larger than 0
“width”, “height” and “width-ratio”:”height-ratio” values cannot be specified simultaneously	Response Header: `"IMG-SKIP-REASON":"cropping: width={value},height={value} and width-ratio={value}:height-ratio={value} values cannot be specified simultaneously"`	Pixels size parameters and aspect ratio are specified simultaneously	Use only one method to specify the “width” and “height” or “width-ratio” and “height-ratio”
x and y percentage parameter cannot be more than 100	Response Header: `"IMG-SKIP-REASON":"cropping: x/y percentage parameter cannot be more than 100"`	The x or y parameter is more than 100%	Set the x and y parameters between 0 and 100 [0, 100]
“offset x”, “offset-y” parameters cannot be more than 100	Response Header: `"IMG-SKIP-REASON":"cropping: offset-x/y parameter cannot be more than 100"`	The “offset-x“ or “offset-y” parameters are more than 100	Specify the “offset-x” and “offset-y” parameters as less than 100
Output “height” and “width” are bigger than the original image size	Response Header: `"IMG-SKIP-REASON":"cropping: output height and width cannot be bigger than the original image size"`	The “height” and “width” parameters are more than the width and height of the original image	Set the height and width parameters to be less than the original image
Output x or y pixel value is bigger than the original image value	Response Header: `"IMG-SKIP-REASON":"cropping: output x/y pixel value cannot be more than the original image pixels"`	The x or y pixel offset positions the crop area so that it extends beyond the original image boundaries	Adjust the x or y pixel offset so that the crop area remains within the original image boundaries
Output x or y percentage value cannot be more than the original image size	Response Header: `"IMG-SKIP-REASON":"cropping: output x/y percentage value cannot be more than the original image size"`	The x or y percentage offset positions the crop area so that it extends beyond the original image boundaries	Adjust the x or y percentage offset so that the crop area remains within the original image boundaries
Crop operation internal error	Response Header: `"IMG-SKIP-REASON":"resizing: fit operation internal error"`	The crop operation failed due to internal reasons	Contact our technical support team at support@gcore.com

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Possible Image Stack errors

Check image details

Common errors that result in a broken image

Errors that return the original image

Compression and quality operation errors

Resize operation errors

Crop operation errors

​Check image details

​Common errors that result in a broken image

​Errors that return the original image

​Compression and quality operation errors

​Resize operation errors

​Crop operation errors

Check image details

Common errors that result in a broken image

Errors that return the original image

Compression and quality operation errors

Resize operation errors

Crop operation errors