What Might Be Wrong

To get support or use this guide, make sure you get the detailed error message from visiting the image URL directly. This guide cannot offer a solution to a generic 500 error, 404 error, or a "broken image icon", as those symptoms are far too generic to be useful. The troubleshooting tips presented here are specific to v4. Switch to the v3 troubleshooting page if you are using v3.

If this page doesn't resolve your issue, visit the Support page.

Server Error in '/' Application. Out of memory.

You might be trying to resize certain large images for the first time. Even a 15MB jpg, however, uncompresses to about 80MB in bitmap form (depending on the compression level). If you are resizing to a 2MB jpg (15MB BMP), memory requirements for the operation are roughly 110MB (15 + 80 + 15). If you plan on using ImageResizer for very high-resolution photos (above 8MP), we suggest making sure you have ample amounts of RAM. 400MB to 1GB is usually plenty for the average web site with disk caching enabled.

Could not load type 'ImageResizer.InterceptModule'

Potential causes:

  1. Your website has a 'sub-site' (Application Folder) inside it. Application Folders inherit all Web.config settings from their parent sites, yet expect to have their own copies of all the dlls referenced by those settings in their own /bin folder. You can resolve this problem by (a) changing the app folder to a virtual folder, (b) adding a copy of ImageResizer.dll and plugins into the /bin folder inside that application also, or (c) using <remove /> statements in the child Web.config to cancel out the inherited <add /> statements from the parent Web.config. Option (c) will disable image resizing within the sub-application.
  2. You didn't copy ImageResizer.dll into the /bin folder.
  3. The ImageResizer.dll file in /bin is corrupt. Verify it has the correct file size and version number, or re-copy it from the download.

The type or namespace name "ImageResizer" could not be found

When using the ImageResizer from a .NET project that is not a web project you may get the following build error:

The type or namespace name "ImageResizer" could not be found (are you missing a using directive or assembly reference?)

This is caused by using a Client Profile version of .NET instead of the Full version. You can change this in Project Properties -> Application -> Target Framework. The ImageResizer requires the full version, as it is also designed to support ASP.NET usage and references the System.Web assembly (which is not part of the client profile version of .NET).

Image appears original size

Potential causes:

  1. You did not register the HttpModule properly in both places of your Web.config file. Verify you can access /resizer.debug. If not, this is the problem.
  2. You are the IIS Classic Pipeline, and are not using the .jpg.ashx syntax, and you have not mapped all requests to the ASP.NET runtime.
  3. You are mistyping the querystring commands.
  4. The original image is smaller than the size you are requesting, and you are not using &scale=both (The default behavior is to never upscale images, but this can be changed).

File not found

Potential causes:

  1. You did not register the HttpModule properly in both places of your Web.config file. Verify you can access /resizer.debug. If not, this is the problem.
  2. You (a) aren't specifying a command string, (b) have Precompilation enabled, and (c) are using an image provider. This is caused by a long-standing bug in the .NET framework.
  3. You have a URL rewriting event that is affecting path names.

This type of page is not served. (HTTP 403 error)

Description: The type of page you have requested is not served because it has been explicitly forbidden. The extension '.jpg' may be incorrect. Please review the URL below and make sure that it is spelled correctly.

Possible causes

  1. You aren't logged in. ImageResizer obeys your URL Authorization rules, so don't expect to view images where you can't visit .aspx pages.
  2. You are trying to access a S3 bucket or Remote URL that is not authorized.

This generic error message often hides a more descriptive message, but that message is always guaranteed to be a "Not Authorized To View this Content" kind of error.

Server object error 'ASP 0178 : 80070005'

Server object error 'ASP 0178 : 80070005'
Server.CreateObject Access Error
The call to Server.CreateObject failed while checking permissions.
Access is denied to this object.

This error usually means that the user that the ASP website is running under does not have NTFS permissions to the ImageResizer dlls.
Right click the C:\Program Files\ImageResizingNet\v3 folder and choose Properties, Security, hit Edit, then click Add, type in the user name your website is running under, hit OK, then check Read & Execute, and hit OK, then Apply.

On IIS6, this account is typically IUSR_ComputerName, but on IIS7, the account is usually NETWORK SERVICE or (if you're not use a default app pool), a custom user account. You'll need to open IIS and inspect the appropriate Application Pool to find out which account you need to give permissions to.

If that fails, providing Readonly access to the Everyone group should work, but that may not be acceptable if you have highly-isolated application pools which you don't want to be able to access the ImageResizer dlls files.

If you still encounter issues, perform a reinstall with COMInstaller.exe, and save the install log. If the reinstall doesn't fix the problem, send the install log to to get help with your issue.

Quality loss when resizing 8-bit Grayscale Jpeg images

This is a known bug in GDI+. GDI+ opens 8-bit grayscale Jpeg images as 4-bit images. Here's the bug report at Microsoft Connect.

The workaround is to use WIC or FreeImage for these requests. Any of the following plugins will solve the problem

  1. WicDecoder - Install, then add &decoder=wic to affected URLs. (best quality)
  2. WicBuilder - Install, then add &builder=wic to affected URLs. Faster, but slightly lower quality than #1 (nearly imperceptible)
  3. FreeImageDecoder - Install, then add &decoder=freeimage
  4. FreeImageBuilder - Install, then add &builder=freeimage. Slowest, but highest quality. with builder=freeimage or builder=wic

Performance issues or error messages when using a SAN.

This is tricky to get right - read the full article here.

Losing transparency when working with GIF images

You must have the PrettyGifs plugin installed to get high-quality, transparent GIF and 8-bit PNG results. You may also want the AnimatedGifs plugin.

SizeLimitException - The dimensions of the output image (4800x2700) exceed the maximum permitted dimensions of 3200x3200.

By default, ImageResizer limits the output size of images to 3200x3200. This can be changed by configuring (or removing) the SizeLimiting plugin.