Atalasoft Knowledge Base

HOWTO: Increase IIS Upload Limit


WingScan (WebCapture) and WebDocumentViewer upload features may fail to upload large numbers of pages / larger files due to limits imposed by the IIS web server

The default upload size is quite small relative to modern needs (it's about 30MiB) 

IMPORTANT: Note that the upload limit values are in BYTES, not Kilobytes or Megabytes.. so if you want 50 MiB, you'd use a value of 524288000

Adjusting Limits (two ways)

To address this, you need to update the IIS Upload limit. There are two methods - Interactively with the IIS Administration snap in, or via Web.Config

Interactively (GUI)

  1. Open IIS 7 Snap-In.
  2. Select the Web site you want enable to accept large file uploads.
  3. In the main window double-click Request filtering.
    • The Request filtering window opens.
    • The tab list shows options such as file name extensions, rules, and hidden segments.
  4. Select one fo the tabs. and in the main window right-click and select Edit Feature Settings.
  5. Modify the Maximum allowed content length (bytes) example: 524288000.

Using Web.Config

Find and edit your existing web.config for your solution

			<requestLimits maxAllowedContentLength="524288000"/>

If you add the above code to the web.config file for your site, you can control the maximum upload size for your site. In many cases, the system.webServer node will already be in the file, so just add the security node within that.

Some notes on WebCapture Upload Limits

As mentioned above: By default, IIS limits uploads to 30MB. If your application may sometimes generate larger uploads, you will need to adjust this limit for the server, or at least for your application.

Estimate upload sizes

The size of an upload is approximately the sum of the compressed sizes of the uploaded images x 4/3 (1.333).

The calculations below are for images. Remember that duplex scanning generates two images per page, minus any blank sides discarded by setting discardBlankPages:true. (note discardBlankPages is a feature that is only supported if you have the VRS feature licensed and enabled)

Raw uncompressed image size

Uncompressed image size in bytes = (width x DPI x height x DPI x depth) / 8

Where depth is 24 for color, 8 for grayscale, and 1 for B&W images.

Example, an 8.5" x 11" color page, scanned at 200 DPI: (8.5 x 200 x 11 x 200 x 24) / 8 = 11,220,000 bytes (~11MB)

Compression ratios

Typical office documents in B&W will compress by ~10X. White space increases the compression, lots of text or detailed graphics of any kind decreases the compression. 50KB per compressed B&W image is not a bad average, 70KB is conservative.

Grayscale and color images will compress by 20X-30X, sometimes more. As with B&W, blank paper compresses more, detailed content compresses less.

For our example 8.5" x 11" color page scanned at 200 DPI, with a raw size of 11MB we estimate a compressed size in the range 374KB - 560KB.

Last Modified: 9 Months Ago
Last Modified By: Tananda
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