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Clarify Local Network Access restrictions in Chromium 142 documentation (#961)
* Clarify Local Network Access restrictions in Chromium 142 documentation
* Update last_modified date in FAQ article
update last_modified timestamp
* update other causes title
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Co-authored-by: Tony-Dynamsoft <112376616+tony-xlh@users.noreply.github.com>
Starting in **Chromium-based browsers v142+** (released Oct 28, 2025)—including Chrome, Edge, Brave, and Opera—Dynamsoft Web TWAIN Service may not work as expected due to new local-network security rules.
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Starting in **Chromium-based browsers v142+** (released Oct 28, 2025)—including Chrome, Edge, Brave, and Opera—Dynamsoft Web TWAIN Service may not work as expected due to new **Local Network Access (LNA)** restrictions that limit requests **from public network locations to private and loopback network locations**.
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### Symptoms
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@@ -41,6 +41,8 @@ from origin 'https://your-domain.com' has been blocked by CORS policy:
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Permission was denied for this request to access the `unknown` address space.
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```
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This error occurs because the web page is loaded from a public network origin (for example, `https://your-domain.com`) and is attempting to connect to a loopback network location (`127.0.0.1`), which Chrome now treats as a protected local network request.
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---
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#### Version-Specific Behavior
@@ -59,10 +61,14 @@ The observed behavior depends on Chromium browser version and Dynamic Web TWAIN
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### Root Cause
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Chromium 142 introduces a new [Local Network Access security policy](https://chromestatus.com/feature/5152728072060928) requirement.
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Requests from web pages to loopback addresses such as `localhost` / `127.0.0.1` are blocked unless the user (or an admin policy) explicitly grants access.
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Chromium 142 introduces and enforces a new [Local Network Access (LNA)](https://chromestatus.com/feature/5152728072060928) security model that restricts requests **from public network locations to private and loopback network locations**, requiring explicit user permission.
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> [!NOTE]
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> For background and design rationale, see Chrome’s Developer Blog: [New permission prompt for Local Network Access](https://developer.chrome.com/blog/local-network-access).
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Under this model, **requests originating from a public network location** (such as a publicly hosted website) **to private or loopback network locations** (including localhost and 127.0.0.1) are blocked by default unless the user explicitly grants permission.
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Because Dynamic Web TWAIN communicates with a local service, these restrictions can prevent normal operation.
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Dynamic Web TWAIN relies on a locally installed service that listens on a loopback address. When a web application hosted on a public domain attempts to communicate with this service, Chrome categorizes the request as a **public-to-local** network request, which now requires explicit user consent.
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### Resolution
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@@ -166,6 +172,6 @@ Here are the details:
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This design will be integrated in v19.3. For old versions, we can include an extra js file, which can be retrieved by contacting [support](mailto://support@dynamsoft.com).
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## Other Causes
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## Other Causes of Failure to Connect to the Service
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There are other causes of service not being connected. You can find them in [another FAQ](/_articles/faq/service-prompting-to-install-repeatedly.md).
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