diff --git a/barcode-reader/web/index.md b/barcode-reader/web/index.md
index af830b4..a014e46 100644
--- a/barcode-reader/web/index.md
+++ b/barcode-reader/web/index.md
@@ -62,7 +62,6 @@ Welcome! Browse the sections below for answers to common questions, configuratio
 - [Difference between BestSpeed and BestCoverage](scan-setting/difference-between-bestspeed-and-bestcoverage.html)
 - [Differences between Full and Compact Editions](scan-setting/differences-between-full-and-compact-editions.html)
 - [Differences between updateScanSettings, updateVideoSettings, and updateRuntimeSettings](scan-setting/differences-between-updateScanSettings-updateVideoSettings-and-updateRuntimeSettings.html)
-- [Troubleshooting - Error: [xxx] No license found](scan-setting/enable-supported-barcode-format.html)
 - [Read Inverted Image](scan-setting/read-inverted-image.html)
 - [Remove Duplicates](scan-setting/remove-duplicates.html)
 - [Unable to Scan Aztec Code](scan-setting/unable-to-scan-aztec-code.html)
diff --git a/barcode-reader/web/scan-setting/index.md b/barcode-reader/web/scan-setting/index.md
index 115fb1f..18922c5 100644
--- a/barcode-reader/web/scan-setting/index.md
+++ b/barcode-reader/web/scan-setting/index.md
@@ -13,7 +13,6 @@ noTitleIndex: true
 - [Difference between BestSpeed and BestCoverage](difference-between-bestspeed-and-bestcoverage.html)
 - [Differences between Full and Compact Editions](differences-between-full-and-compact-editions.html)
 - [Differences between updateScanSettings, updateVideoSettings, and updateRuntimeSettings](differences-between-updateScanSettings-updateVideoSettings-and-updateRuntimeSettings.html)
-- [Enable Supported Barcode Format](enable-supported-barcode-format.html)
 - [Read Inverted Image](read-inverted-image.html)
 - [Remove Duplicates](remove-duplicates.html)
 - [Unable to Scan Aztec Code](unable-to-scan-aztec-code.html)
diff --git a/barcode-reader/web/scan-setting/enable-supported-barcode-format.md b/license/enable-supported-barcode-format.md
similarity index 99%
rename from barcode-reader/web/scan-setting/enable-supported-barcode-format.md
rename to license/enable-supported-barcode-format.md
index bb2d419..772794d 100644
--- a/barcode-reader/web/scan-setting/enable-supported-barcode-format.md
+++ b/license/enable-supported-barcode-format.md
@@ -1,6 +1,6 @@
 ---
 layout: default-layout
-title: Troubleshooting - Error: [xxx] No license found
+title: Error [xxx] No license found
 keywords: Dynamsoft Barcode Reader, FAQ, JavaScript, tech basic, barcode format, no license found
 description: When moving from a trial license to a production license, you may encounter the error `[xxx] No license found` if your enabled barcode formats don't match the formats supported by your license?
 needAutoGenerateSidebar: false
diff --git a/license/index.md b/license/index.md
index 93f20e0..d4ddeca 100644
--- a/license/index.md
+++ b/license/index.md
@@ -20,3 +20,5 @@ Please use the links below to find answers to common questions and configuration
 - [How to track license usage?](track-license.html)
 - [New license required for per-device licensing?](new-license-required-per-device-licensing.html)
 - [How to get a free trial?](dbr-free-trial.html)
+- [Troubleshooting - Error: [xxx] No license found](enable-supported-barcode-format.html)
+- [Troubleshooting - Error: -20151 Unauthorized Device Clone Detected](troubleshooting-unauthorized-device-clone-detected.html)
\ No newline at end of file
diff --git a/license/troubleshooting-unauthorized-device-clone-detected.md b/license/troubleshooting-unauthorized-device-clone-detected.md
new file mode 100644
index 0000000..e0596a2
--- /dev/null
+++ b/license/troubleshooting-unauthorized-device-clone-detected.md
@@ -0,0 +1,57 @@
+---
+layout: default-layout
+title: Error -20151 Unauthorized Device Clone Detected
+keywords: Dynamsoft Barcode Reader, Error -20151, Unauthorized Device Clone, License Error, DBR FAQ, License Validation
+description: Understand the cause of error -20151 Unauthorized Device Clone Detected in Dynamsoft Barcode Reader and how to resolve it.
+needAutoGenerateSidebar: false
+---
+
+# Troubleshoot - Error -20151 — Unauthorized Device Clone Detected
+
+## What does error **-20151** mean?
+
+The error **-20151: Unauthorized device clone detected** indicates that the license system has identified abnormal behavior suggesting that the same license is being used on what appears to be a cloned or altered device environment.
+
+This is a **security protection mechanism** designed to prevent license misuse.
+
+---
+
+## 🔍 Common Causes
+
+### 1️⃣ System Time Was Modified
+If the **system date or time was manually changed** (for example, rolling the clock backward or forward), the license validation logic may interpret this as a potential cloning or tampering attempt.
+
+Typical scenarios include:
+- Manual system time adjustment  
+- Time rollback after OS restore or snapshot  
+- VM snapshot restore with outdated system time  
+
+---
+
+### 2️⃣ Switching SDK Versions Within a Short Period of Time
+Rapidly **switching between different SDK versions** (for example, upgrading and downgrading, or running multiple major versions back-to-back) within a short timeframe can also trigger this error.
+
+This may happen when:
+- Testing multiple SDK versions on the same machine  
+- Running parallel applications using different SDK versions  
+- Rolling back to an older version shortly after upgrading  
+
+The license system may treat this as an abnormal environment change.
+
+---
+
+## ✅ Recommended Solutions
+
+- Ensure the **system time is correct** and synchronized with an official time source.
+- Avoid frequently switching between different SDK versions on the same device.
+- If testing multiple versions is required, allow sufficient time between version changes.
+- Restart the system after correcting time settings or completing upgrades.
+
+---
+
+## 📩 Still Experiencing the Issue?
+
+If the issue persists after verifying the above:
+- Please contact our support team.
+- Provide your **license key**, **SDK version**, and a brief description of your environment and recent changes.
+