---
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title: Dynamic Web TWAIN SDK FAQ
keywords: Dynamic Web TWAIN, Documentation, FAQ
breadcrumbText: FAQ
description: Dynamic Web TWAIN SDK Documentation FAQ
---
# FAQ 

## SDK Download/Free Trial

1.  [How can I extend my free trial?](/_articles/faq/extend-free-trial.md)
2.  [Where can I download an older version of the Dynamic Web TWAIN SDK?](/_articles/faq/download-older-version-sdk.md)
3.  [Do you provide free trial versions of the Dynamic Web TWAIN SDK?](/_articles/faq/provide-free-trial-version.md)
4.  [Can I run the scanning service on an ARM-based embedded device, such as Raspberry Pi?](/_articles/faq/run-on-arm-based-embedded-device.md)
5.  [Do you also provide an SDK download for Linux and Mac developers?](/_articles/faq/sdk-download-for-linux-and-mac.md)
6.  [Is the free trial version fully functional?](/_articles/faq/trial-fully-functional.md)
7.  [Can I use the Dynamic Web TWAIN SDK to create a PWA application?](/_articles/faq/use-with-PWA.md)

## Capture/Image Source

1.  [Download virtual scanner for testing](/_articles/faq/download-virtual-scanner-for-testing.md)
2.  [What physical document scanners does the Dynamic Web TWAIN SDK support?](/_articles/faq/what-physical-scanners-are-supported.md)
3.  [How can I verify if my physical document scanner works with the Dynamic Web TWAIN SDK?](/_articles/faq/verify-if-device-is-supported.md)
4.  [How to use TWACKER to check if your device is TWAIN Compliant?](/_articles/faq/how-to-use-TWACKER-to-check-if-your-device-is-TWAIN-Compliant.md)
5.  [How to test if your scanner supports ICA scanning on Mac OS?](/_articles/faq/how-to-test-if-your-scanner-supports-ICA-scanning-on-Mac-OS.md)
6.  [How to test if your device is SANE compliant?](/_articles/faq/how-to-test-if-your-device-is-SANE-compliant.md)
7.  [How to test if your camera is DirectShow compliant?](/_articles/faq/how-to-test-if-your-camera-is-DirectShow-compliant.md)
8.  [Can I set scanning settings without using the default scanner's UI? What pre-scanning settings do you support?](/_articles/faq/setting-scan-settings-without-ui.md)
9.  [Can I hide offline scanner devices from the select source list?](/_articles/faq/hide-offline-scanners-from-source-list.md)
10.  [Can I hide webcam devices from the select source list?](/_articles/faq/hide-webcam-from-source-list.md)
11.  [What are the differences between TWAIN and WIA?](/_articles/faq/difference-between-Twain-and-wia.md)
12.  [How to exclude WIA sources in the source list?](/_articles/faq/how-to-exclude-wia-sources-in-the-source-list.md)
13.  [How can I set the last selected source as the default source for an end user?](/_articles/faq/last-selected-sourcename.md)
14.  [How can I limit all users to use a specific scanner model?](/_articles/faq/limit-to-specific-scanner.md)
15.  [Can the Dynamic Web TWAIN SDK automatically remove blank pages during the document scanning process?](/_articles/faq/remove-blank-page-automatically.md)
16.  [Can the Dynamic Web TWAIN SDK automatically rotate upside-down pages during the document scanning process?](/_articles/faq/automatically-rotate-upside-down-pages.md)
17.  [Can the Dynamic Web TWAIN SDK automatically detect borders of the scanned document and crop it out?](/_articles/faq/automatically-detect-border.md)
18.  [Can I set my document scanner to scan x number of pages instead of all pages from the automatic document feeder (ADF)?](/_articles/faq/scan-x-pages-from-automatic-document-feeder.md)
19.  [Can the Dynamic Web TWAIN SDK detect whether papers exist in the feeder?](/_articles/faq/detect-paper-on-feeder.md)
20.  [How can I get a list of supported resolution/DPI values from the document scanner?](/_articles/faq/list-supported-resolution-DPI.md)
21.  [How can I use a custom capability of my scanner hardware when there is no direct API to set it?](/_articles/faq/custom-capability.md)
22.  [Is there a limit on the number of pages I can scan at a time? Where do you store them after scanning?](/_articles/faq/limit-on-scanned-pages.md)
23.  [Document scanning via the Dynamic Web TWAIN SDK is slower than using the native scanner application. How can I speed it up?](/_articles/faq/document-scanning-slow-than-native.md)
24.  [Can I use built-in or USB webcam to capture document?](/_articles/faq/use-usb-webcam-to-capture.md)
25.  [Can I import existing images or PDF documents using the Dynamic Web TWAIN SDK?](/_articles/faq/import-existing-documents-or-images.md)
26.  [Can I download an image from a FTP or HTTP server using the Dynamic Web TWAIN SDK?](/_articles/faq/download-image-from-FTP-or-HTTP-server.md)
27.  [How can I trigger an automatic workflow right after document scanning or image importing?](/_articles/faq/trigger-automatic-workflow-after-scanning.md)
28.  [Do you support capturing documents from mobile cameras?](/_articles/faq/support-capture-from-mobile-camera.md)
29.  [How to scan documents on mobile devices?](/_articles/faq/how-to-scan-documents-on-mobile-devices.md)
30.  [Do you support fingerprint or medical imaging devices?](/_articles/faq/fingerprint-medical-imaging.md)
31.  [Is the AcquireImage() method synchronous or asynchronous?](/_articles/faq/acquireimage-sync-or-async.md)
32.  [How can I support WIA scanner drivers in my application?](/_articles/faq/support-wia-scanner-drivers.md)
33.  [Why are my images coming out distorted in MacOS Sonoma?](/_articles/faq/macos-sonoma-distorted-scans.md)

## Image Viewer

1.  [Where is the image viewer object defined?](/_articles/faq/image-viewer-object-defined.md)
2.  [Can the size of the image viewer auto resize when the browser window size changes?](/_articles/faq/viewer-size-auto-resize.md)
3.  [How can I create a thumbnail viewer to view images?](/_articles/faq/create-thumbnail-viewer-to-navigate-images.md)
4.  [How can I change the background color of the image viewer?](/_articles/faq/change-background-color.md)
5.  [How can I reorder images in the viewer?](/_articles/faq/resort-images-in-viewer.md)
6.  [How can I disable drag and drop images in the viewer?](/_articles/faq/disable-drag-and-drop-in-images.md)
7.  [How can I show multiple images at a time?](/_articles/faq/show-multiple-images.md)
8.  [How can I show page number on each image?](/_articles/faq/show-page-number.md)
9.  [How can I resize the view of image (e.g. zoom in/out on an image)?](/_articles/faq/resize-view-of-image.md)
10.  [What mouse click events does the viewer support?](/_articles/faq/mouse-click-events-supported.md)
11.  [How can I insert an image after a selected image in the viewer?](/_articles/faq/insert-image-after-selected-image.md)
12.  [Can I protect sensitive information of an image from being seen?](/_articles/faq/protect-sensitive-information.md)
13.  [Can I hide the Dynamsoft image viewer and use my own image viewer?](/_articles/faq/hide-image-viewer.md)
14.  [Can I print images from the viewer?](/_articles/faq/print-images-from-viewer.md)
15.  [How to get the coordinates of the selected area on an image?](/_articles/faq/coordinates-of-selected-area.md)

## Image Editing

1.  [What image editing operations does the Dynamic Web TWAIN SDK support?](/_articles/faq/what-image-editing-operation-supported.md)
2.  [How can I show the default image editor tool?](/_articles/faq/show-default-image-editor.md)
3.  [Do you support image deskew?](/_articles/faq/support-image-deskew.md)
4.  [How can I configure all scanned images to conform to a specific size standard (e.g., A4)?](/_articles/faq/set-page-size.md)
5.  [Can I add annotation to an image (e.g. add watermark or text)?](/_articles/faq/add-annotation-to-image.md)
6.  [Can I change the resolution/DPI of an image in the viewer?](/_articles/faq/change-resolution-of-image.md)
7.  [Can I convert a color image to grayscale or black & white?](/_articles/faq/convert-color-image-to-grayscale.md)
8.  [Is there an undo functionality?](/_articles/faq/undo-functionality.md)
9.  [How can I remove only the selected images?](/_articles/faq/remove-selected-images.md)

## UI Customization

1.  [Is the UI of the Dynamic Web TWAIN SDK fully customizable? What cannot be customized?](/_articles/faq/is-ui-customizable.md)
2.  [How can I change the display language of all messages from English to another language?](/_articles/faq/change-display-language.md)
3.  [How can I change/hide the spinner which shows during document scanning?](/_articles/faq/change-hide-spinner.md)
4.  [How can I change/hide the UI of the progress bar when importing or uploading images?](/_articles/faq/hide-progress-bars.md)
5.  [Can I customize UI elements of the built-in image editor?](/_articles/faq/customize-ui-elements-of-image-editor.md)
6.  [Can I stop the scanner from showing its default popup when there is a paper jam?](/_articles/faq/stop-default-scanner-popup.md)
7.  [Why I cannot hide the loading bar (spinner)?](/_articles/faq/unable-hide-loading-bar.md)

## Document Saving

1.  [What image and document formats can I save my documents as?](/_articles/faq/image-document-formats-save.md)
2.  [What type of HTTP servers do you support? Do you support other server types?](/_articles/faq/http-servers-support.md)
3.  [How can I enable HTTPS support?](/_articles/faq/enable-https-support.md)
4.  [How can I get the smallest size of documents in PDF, TIFF or JPEG format?](/_articles/faq/smallest-size-documents.md)
5.  [How can I automatically trigger actions when images arrive on my server side?](/_articles/faq/trigger-actions-server-side.md)
6.  [Can I upload documents to a different website domain?](/_articles/faq/upload-documents-to-different-domain.md)
7.  [How can I get a response string from my HTTP Server if the upload succeeds or fails?](/_articles/faq/response-string-from-server-on-upload.md)
8.  [Can I upload documents via a background service outside the web browser?](/_articles/faq/upload-using-background-service.md)
9.  [Can I insert newly scanned pages to an existing document?](/_articles/faq/insert-new-pages-to-existing-document.md)
10.  [How can I upload a JSON file to my server?](/_articles/faq/upload-json-files-to-server.md)
11.  [How can I save selected images instead of all images to my server or database?](/_articles/faq/save-selected-images-to-server.md)
12.  [How to use a blank page as a separator?](/_articles/faq/use-blank-page-as-a-separator.md)
13.  [How to upload multiple files at a time?](/_articles/faq/upload-multiple-files-at-a-time.md)
14.  [How to deploy your own upload server with ASP.NET?](/_articles/faq/deploy-your-own-upload-server-with-asp.net.md)
15.  [How to deploy your own upload server with JSP?](/_articles/faq/deploy-your-own-upload-server-with-jsp.md)
16.  [How to deploy your own upload server with Node.js?](/_articles/faq/deploy-your-own-upload-server-with-node.js.md)
17.  [How to deploy your own upload server with PHP?](/_articles/faq/deploy-your-own-upload-server-with-php.md)

## Security

1.  [Where does the Dynamic Web TWAIN SDK store images on end-user machines? Are they encrypted?](/_articles/faq/where-images-are-stored.md)
2.  [Can I prompt the end-user when the Dynamic Web TWAIN SDK attempts to visit any local resources (scanner, camera, or disk drive)?](/_articles/faq/prompt-end-user-when-local-resources-used.md)
3.  [When are the locally cached images destroyed?](/_articles/faq/local-cached-images-destroyed.md)
4.  [The license key is set in JavaScript. How can I protect it?](/_articles/faq/license-key-protection.md)
5.  [Does the Dynamic Web TWAIN SDK use any deprecated technologies like NPAPI or ActiveX?](/_articles/faq/use-deprecated-technology.md)
6.  [How can I securely transfer scanned documents to my server?](/_articles/faq/securely-transfer-to-server.md)
7.  [Can I generate/load an encrypted file in PDF format?](/_articles/faq/encrypt-pdf-files.md)
8.  [Can I limit the size of documents to be uploaded to my server?](/_articles/faq/limit-upload-size-to-server.md)
9.  [Is the Dynamic Web TWAIN SDK ISO 27001 compliant?](/_articles/faq/iso-27001-compliant.md)
10.  [Is the Dynamic Web TWAIN SDK GDPR compliant?](/_articles/faq/gdpr-compliant.md)
11.  [Is the Dynamic Web TWAIN SDK HIPAA compliant?](/_articles/faq/hipaa-compliant.md)
12.  [How can I change the certificate of the Dynamic Web TWAIN Service?](/_articles/faq/change-dynamsoft-service-certificate.md)

## Addon

1.  [Do I need a separate license for each addon?](/_articles/faq/separate-license-for-addon.md)
2.  [When do I need PDF Rasterizer Addon? Can I load existing PDF files into the Dynamic Web TWAIN SDK without the PDF Rasterizer addon?](/_articles/faq/when-is-pdf-rasterizer-needed.md)
3.  [How can I load PDF/A files into the Dynamic Web TWAIN SDK?](/_articles/faq/load-pdf-files.md)
4.  [Can I load specific page numbers of a PDF file into the viewer?](/_articles/faq/load-specific-page-of-pdf-to-viewer.md)
5.  [Do I need the PDF Rasterizer addon to convert scanned documents to PDF files?](/_articles/faq/is-pdf-rasterizer-needed-to-convert-scanned-documents-to-pdf.md)
6.  [How can I generate PDF/A files?](/_articles/faq/generate-pdf-files.md)
7.  [Does your Barcode Reader addon support patch code?](/_articles/faq/does-barcode-addon-support-patch-code.md)
8.  [How can I separate my documents automatically by barcode?](/_articles/faq/separate-documents-by-barcode.md)
9.  [Is there any way to speed up the barcode reading process?](/_articles/faq/speed-up-barcode-reading-process.md)
10.  [What types of webcams does the Webcam Capture addon support](/_articles/faq/webcam-supported-by-webcam-capture-addon.md)
11.  [How can I prompt users for a password when loading a password-protected PDF?](/_articles/faq/prompt-password-for-protected-pdf.md)

## Project Deployment and End-user Installation

1.  [What are the Resources files?](/_articles/faq/what-are-the-resources-files.md)
2.  [What resources of the SDK should be included in my web application?](/_articles/faq/resources-to-be-included-in-SDK.md)
3.  [How can I change the reference path to the Dynamsoft resources in my project?](/_articles/faq/change-reference-path.md)
4.  [What is Remote Scan and how do I enable it?](https://www.dynamsoft.com/remote-scan/docs/introduction/)
5.  [How can I use Dynamic Web TWAIN in a Citrix environment?](/_articles/faq/use-dwt-in-citrix-env.md)
6.  [Is there any component of the Dynamic Web TWAIN SDK that needs to be installed on end-user machines?](/_articles/faq/component-needs-to-be-installed-on-end-user-machine.md)
7.  [What does the Dynamic Web TWAIN Service do on the end-user machine?](/_articles/faq/what-does-dynamsoft-service-do-on-end-user-machine.md)
8.  [Are admin privileges required to install the end-user component?](/_articles/faq/admin-privileges-needed-to-install.md)
9.  [Can I install Dynamic Web TWAIN Service silently?](/_articles/faq/can-i-install-dynamsoft-service-silently.md)
10.  [Is there an easy way to deploy the end-user components to all users?](/_articles/faq/deploy-to-all-users.md)
11.  [How to uninstall Dynamic Web TWAIN Service?](/_articles/faq/how-to-uninstall-dynamsoft-service.md)
12.  [I have installed the Dynamic Web TWAIN Service on an end-user machine but still got asked to install it repeatedly. Why?](/_articles/faq/service-prompting-to-install-repeatedly.md)
13.  [Dynamic Web TWAIN Service installation and uninstallation issue](/_articles/faq/service-installation-issue.md)
14.  [Can I use two different websites integrated with two different versions of Dynamic Web TWAIN on the same computer?](/_articles/faq/service-backward-compatibility.md)
15.  [How do I upgrade my project to use the latest version of the Dynamic Web TWAIN SDK?](/_articles/faq/upgrade-to-latest-version.md)
16.  [How do I upgrade the end-user installation for all end users once I upgrade my project?](/_articles/faq/upgrade-end-user-installations.md)
17.  [Can I still use Dynamic Web TWAIN on non-HTTPS (insecure HTTP) sites with Chrome?](/_articles/faq/http-insecure-websites-in-chromium-browser.md)
18.  [How to resolve Dynamic Web TWAIN issue in Chrome 101?](/_articles/faq/private-network-access-in-chrome101.md)
19.  [Dynamic Web TWAIN – Content-Security-Policy violated](/_articles/faq/content-security-policy-violated.md)
20.  [Scanner source is listed on XSane application but not on my web application on Linux machines](/_articles/faq/source-not-listed-on-linux.md)
21.  [How to run Dynamic Web TWAIN ActiveX in Microsoft Edge Internet Explorer (IE) mode](/_articles/faq/activeX-in-Edge-IE-mode.md)
22.  [The scanner's UI or the system's file dialog does not open when scanning](/_articles/faq/service-is-blocked.md)
23.  [How do I know which SDK version I am using?](/_articles/faq/find-SDK-version.md)
24.  [Where can I download the Dynamic Web TWAIN Service installers only?](/_articles/faq/download-service-only.md)
25.  [Error message - CORS Errors caused by local network access permissions when using Chromium 142 and later](/_articles/faq/chromium-142-local-network-access-issue.md)
26.  [macOS Rosetta Discontinuation and Dynamic Web TWAIN Service](/_articles/faq/mac-rosetta-discontinuation.md)

## Error Troubleshooting

1.  [General troubleshooting steps](/_articles/faq/general-troubleshooting-steps.md)
2.  [General failure](/_articles/faq/general-failure.md)
3.  [A connection with the server could not be established](/_articles/faq/connection-couldnt-be-established.md)
4.  [HTTP request error](/_articles/faq/HTTP-request-error.md)
5.  [HTTP process error](/_articles/faq/HTTP-process-error.md)
6.  [Only 24-bit true color bmp and 8-bit gray-scaled images are supported for JPEG compression](/_articles/faq/JPEG-compression.md)
7.  [XMLHttpRequest cannot load XXX](/_articles/faq/XMLHttpRequest-cannot-load.md)
8.  [Source is connected to the maximum supported number of applications](/_articles/faq/source-connected-to-maximum.md)
9.  [Sequence error](/_articles/faq/sequence-error.md)
10.  [Request header field dwt-md5 is not allowed by Access-Control-Allow-Headers in preflight response](/_articles/faq/dwt-md5-is-not-allowed.md)
11.  [The handle is in the wrong state for the requested operation](/_articles/faq/the-handle-is-in-the-wrong-state-for-the-requested-operation.md)
12.  [The connection with the server was terminated abnormally](/_articles/faq/the-connection-with-the-server-was-terminated-abnormally.md)
13.  [Syntax error – Unexpected Token "<"](/_articles/faq/syntax-error-unexpected-token.md)
14.  [Uncaught ReferenceError - DVS is not defined](/_articles/faq/DVS-is-not-defined.md)
15.  [Error message - The current product key does not support XXX, please contact the site administrator](/_articles/faq/error-message-current-product-key-does-not-support.md)
16.  [Error message - The current product key does not support current OS for embed device, please contact the site administrator](/_articles/faq/error-message-product-key-does-not-support-current-os.md)
17.  [Error message - The current product key is empty or invalid, please contact the site administrator](/_articles/faq/error-message-current-product-key-is-empty-or-invalid.md)
18.  [Error message - The current product key is missing the core license, please contact the site administrator](/_articles/faq/error-message-product-key-is-missing-the-core-license.md)
19.  [Error message - The domain of your current site does not match the domain bound in the current product key, please contact the site administrator](/_articles/faq/error-message-domain-of-site-doesnt-match-domain-bound-to-product-key.md)
20.  [Error message - The current product key is invalid because it's generated with the licenses of a different major version](/_articles/faq/error-message-license-generated-with-license-of-major-version.md)
21.  [Error message - The current product key is not for full/trial version, please contact the site administrator](/_articles/faq/error-message-product-key-is-not-for-full-version.md)
22.  [Error message – Your Dynamic Web TWAIN product key expired](/_articles/faq/error-message-product-key-expired.md)
23.  [Error Message - Failed to load resource: net::ERR\_CERT\_DATE\_INVALID](/_articles/faq/failed-to-load-resource.md)
24.  [Error Message - The connection from the insecure (HTTP) web page to the local 'Dynamsoft Service' failed](/_articles/faq/connection-from-the-insecure-HTTP-to-service-failed.md)
25.  [Error Message - Source has nothing to capture](/_articles/faq/source-has-nothing-to-capture.md)
26.  [Warning Message - Canvas2D: Multiple readback operations using getImageData are faster with the willReadFrequently attribute set to true](/_articles/faq/chrome-106-107-warning.md)
27.  [Error Message - Uncaught TypeError: Cannot read properties of null (reading 'appendChild') or Failed to execute 'appendChild' on 'Node': parameter 1 is not of type 'Node'](/_articles/faq/type-error-appendchild.md)
28.  [Error Message - User cancelled the operation](/_articles/faq/error-message-user-cancelled-the-operation.md)
29.  [The loading bar keeps spinning when capture the image with iPhone.](/_articles/faq/the-loading-bar-keeps-spinning-when-capture-the-image-with-iphone.md)
30.  [How to debug on Dynamic Web TWAIN online demo?](/_articles/faq/debug-on-online-demo.md)
31.  [Dynamic Web TWAIN prompts the .deb installer for Windows](/_articles/faq/incorrect-installer-for-windowsARM64.md)
32.  [Why am I unable to load the TIFF file into Dynamic Web TWAIN?](/_articles/faq/unable-to-load-4-bit-tiff.md)
33.  [Error message - CORS Errors caused by local network access permissions when using Chromium 142 and later](/_articles/faq/chromium-142-local-network-access-issue.md)
34.  [Error message - File is Damaged and Can’t Be Opened in macOS](/_articles/faq/file-damaged-on-macos.md)
35.  [File Dialog Closes Immediately on Linux](/_articles/faq/file-dialog-on-linux.md)

## Licensing and Purchase

1.  [Is internet connectivity required to use all licenses?](/_articles/faq/is-internet-connectivity-required.md)
2.  [Does the per-server license allow unlimited number of client devices and end users?](/_articles/faq/does-per-server-allow-unlimited.md)
3.  [What license should I purchase if I am providing SaaS?](/_articles/faq/which-license-purchase-needed-for-saas.md)
4.  [For the per-client-device licensing model, can seats taken by retired/unused devices be released from the license?](/_articles/faq/release-license-seats.md)
5.  [Will a client machine take an additional license seat if its operating system is reinstalled?](/_articles/faq/seat-taken-if-os-reinstalled.md)
6.  [What if I reach the limit of the granted number of license seats?](/_articles/faq/license-limit-reached.md)
7.  [Do you offer lifetime/perpetual licenses?](/_articles/faq/offer-perpetual-license.md)
8.  [Do I need to purchase a license for my dev or testing environment?](/_articles/faq/purchase-dev-or-test-license.md)
9.  [I need to resell the SDK within my application to my customers. What options do you offer?](/_articles/faq/resell-sdk.md)
10.  [Are you flexible to discuss custom licensing models?](/_articles/faq/flexible-to-custom-license.md)
11.  [Do you have any local resellers from whom I can purchase a license of the Dynamic Web TWAIN SDK?](/_articles/faq/local-resellers.md)
12.  [Do I get free upgrade if there is a newer version available?](/_articles/faq/free-upgrade.md)
13.  [What is your discount policy?](/_articles/faq/discount-policy.md)
14.  [What's your refund policy?](/_articles/faq/refund-policy.md)

## Annotation

1.  [How can I add annotations to an image and then save/upload it?](/_articles/faq/dwt-with-annotation.md)