Citrix Virtual Apps and Desktops

TWAIN Redirection

April 30, 2025

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Introduction

Users can scan documents from applications within Citrix HDX sessions using TWAIN compliant scanners connected to the client endpoint. The Citrix scanning module redirects the scan request to the client endpoint to process the request. Upon completion, the scanned information is sent to back to the VDA host.

Requirements

Citrix Control Plane

Citrix Virtual Apps and Desktops 1912 or later
Citrix DaaS

Session Host

Operating system
- Windows 10 1809 or later
- Windows 11
- Windows Server 2022 or later
VDA
- Version 1912 or later
Application
- 32-bit application
- 64-bit application

Note:

To enable scanning functionality for 64-bit applications on the session host, the 64-bit TWAIN Data Source Manager (twaindsm.dll) is necessary. This component is not pre-installed by the operating system.

If your 64-bit scanning application does not include this file, please contact the application vendor to acquire the 64-bit twaindsm.dll.

Once obtained, administrators must manually copy the file into the System32 folder on the session host and then restart the machine.

Client Device

Operating system
- Windows 10 1809 or later
- Windows 11
Workspace app
- Windows: version 1912 or later
Scanner
- TWAIN-compliant scanner
- Install TWAIN drivers on the client endpoint

Configuration

TWAIN redirection is enabled by default. The following policy settings are available to configure TWAIN redirection and optimize the scanning experience.

Client TWAIN device redirection: to enable or disable TWAIN redirection.
TWAIN compression level: to set compression levels for images trnasferred from the client to the VDA.

For more details, see TWAIN devices policy settings.

Troubleshooting

TWAIN redirection functionality can be tested with a publicly available test app Twacker, which can be downloaded from this URL.

Follow the steps to validate TWAIN functionality within an HDX session:

Install Twacker on the VDA host.
Launch Twacker (32-bit or 64-bit version).
Click File > Select Source and select your scanner from the list.
Click File > Acquire.
Click the Scan button to test your scanner.

If Twacker can scan successfully, it confirms that the Citrix Virtual Apps and Desktops setup is:

Correctly configured to use TWAIN redirection
Meeting all local client device requirements

If you still have scanning issues within a particular application, then it’s likely to be a software issue.

The official version of this content is in English. Some of the Cloud Software Group documentation content is machine translated for your convenience only. Cloud Software Group has no control over machine-translated content, which may contain errors, inaccuracies or unsuitable language. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, suitability, or correctness of any translations made from the English original into any other language, or that your Cloud Software Group product or service conforms to any machine translated content, and any warranty provided under the applicable end user license agreement or terms of service, or any other agreement with Cloud Software Group, that the product or service conforms with any documentation shall not apply to the extent that such documentation has been machine translated. Cloud Software Group will not be held responsible for any damage or issues that may arise from using machine-translated content.

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TWAIN Redirection

April 30, 2025

Contributed by:

April 30, 2025

Contributed by:

TWAIN Redirection

Introduction

Requirements

Citrix Control Plane

Session Host

Client Device

Configuration

Troubleshooting

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