diff --git a/src/NppJsonViewer/Define.h b/src/NppJsonViewer/Define.h
index a79064c..c7fa177 100644
--- a/src/NppJsonViewer/Define.h
+++ b/src/NppJsonViewer/Define.h
@@ -42,10 +42,11 @@ const TCHAR JSON_ERROR_TITLE[]   = TEXT("JSON Viewer: Error");
 const TCHAR JSON_WARNING_TITLE[] = TEXT("JSON Viewer: Warning");
 const TCHAR JSON_INFO_TITLE[]    = TEXT("JSON Viewer: Information");
 
-const TCHAR JSON_ERR_PARSE[]            = TEXT("Cannot parse JSON. Please select a JSON string.");
-const TCHAR JSON_ERR_VALIDATE[]         = TEXT("There was an error while parsing JSON. Refer to the current selection for possible problematic area.");
-const TCHAR JSON_ERR_VALIDATE_SUCCESS[] = TEXT("JSON looks good. No errors found while validating it.");
-const TCHAR JSON_ERR_SAVE_SETTING[]     = TEXT("Failed to save the settings. Please try again.");
+const TCHAR JSON_ERR_PARSE[]            = TEXT("Unable to parse JSON. Please ensure a valid JSON string is selected.");
+const TCHAR JSON_ERR_VALIDATE[]         = TEXT("An error occurred while parsing the JSON. Check the current selection for the potential issue.");
+const TCHAR JSON_ERR_VALIDATE_SUCCESS[] = TEXT("The JSON appears valid. No errors were found during validation.");
+const TCHAR JSON_ERR_SAVE_SETTING[]     = TEXT("Could not save the settings. Please try again.");
+const TCHAR JSON_ERR_MULTI_SELECTION[]  = TEXT("Multiline selection is not currently supported in Json Viewer.");
 
 const TCHAR STR_VERSION[]     = TEXT("Version: ");
 const TCHAR STR_COPY[]        = TEXT("Copy");
diff --git a/src/NppJsonViewer/JsonViewDlg.cpp b/src/NppJsonViewer/JsonViewDlg.cpp
index 2049cad..3513b6b 100644
--- a/src/NppJsonViewer/JsonViewDlg.cpp
+++ b/src/NppJsonViewer/JsonViewDlg.cpp
@@ -73,10 +73,19 @@ void JsonViewDlg::ShowDlg(bool bShow)
 
 void JsonViewDlg::FormatJson()
 {
-    const auto selectedText              = m_pEditor->GetJsonText();
+    const auto selectedData = m_pEditor->GetJsonText();
+    const auto selectedText = IsSelectionValidJson(selectedData);
+
+    if (!selectedText.has_value() || selectedText.value().empty())
+    {
+        const std::wstring msg = IsMultiSelection(selectedData) ? JSON_ERR_MULTI_SELECTION : JSON_ERR_PARSE;
+        ShowMessage(JSON_INFO_TITLE, msg, MB_OK | MB_ICONINFORMATION);
+        return;
+    }
+
     auto [le, lf, indentChar, indentLen] = GetFormatSetting();
 
-    Result res = JsonHandler(m_pSetting->parseOptions).FormatJson(selectedText, le, lf, indentChar, indentLen);
+    Result res = JsonHandler(m_pSetting->parseOptions).FormatJson(selectedText.value(), le, lf, indentChar, indentLen);
 
     if (res.success)
     {
@@ -85,7 +94,7 @@ void JsonViewDlg::FormatJson()
     }
     else
     {
-        if (CheckForTokenUndefined(JsonViewDlg::eMethod::FormatJson, selectedText, res, NULL))
+        if (CheckForTokenUndefined(JsonViewDlg::eMethod::FormatJson, selectedText.value(), res, NULL))
             return;
 
         ReportError(res);
@@ -94,10 +103,17 @@ void JsonViewDlg::FormatJson()
 
 void JsonViewDlg::CompressJson()
 {
-    // Get the current scintilla
-    const auto selectedText = m_pEditor->GetJsonText();
+    const auto selectedData = m_pEditor->GetJsonText();
+    const auto selectedText = IsSelectionValidJson(selectedData);
 
-    Result res = JsonHandler(m_pSetting->parseOptions).GetCompressedJson(selectedText);
+    if (!selectedText.has_value() || selectedText.value().empty())
+    {
+        const std::wstring msg = IsMultiSelection(selectedData) ? JSON_ERR_MULTI_SELECTION : JSON_ERR_PARSE;
+        ShowMessage(JSON_INFO_TITLE, msg, MB_OK | MB_ICONINFORMATION);
+        return;
+    }
+
+    Result res = JsonHandler(m_pSetting->parseOptions).GetCompressedJson(selectedText.value());
 
     if (res.success)
     {
@@ -106,7 +122,7 @@ void JsonViewDlg::CompressJson()
     }
     else
     {
-        if (CheckForTokenUndefined(JsonViewDlg::eMethod::GetCompressedJson, selectedText, res, NULL))
+        if (CheckForTokenUndefined(JsonViewDlg::eMethod::GetCompressedJson, selectedText.value(), res, NULL))
             return;
 
         ReportError(res);
@@ -115,10 +131,19 @@ void JsonViewDlg::CompressJson()
 
 void JsonViewDlg::SortJsonByKey()
 {
-    const auto selectedText              = m_pEditor->GetJsonText();
+    const auto selectedData  = m_pEditor->GetJsonText();
+    const auto selectedText = IsSelectionValidJson(selectedData);
+
+    if (!selectedText.has_value() || selectedText.value().empty())
+    {
+        const std::wstring msg = IsMultiSelection(selectedData) ? JSON_ERR_MULTI_SELECTION : JSON_ERR_PARSE;
+        ShowMessage(JSON_INFO_TITLE, msg, MB_OK | MB_ICONINFORMATION);
+        return;
+    }
+
     auto [le, lf, indentChar, indentLen] = GetFormatSetting();
 
-    Result res = JsonHandler(m_pSetting->parseOptions).SortJsonByKey(selectedText, le, lf, indentChar, indentLen);
+    Result res = JsonHandler(m_pSetting->parseOptions).SortJsonByKey(selectedText.value(), le, lf, indentChar, indentLen);
 
     if (res.success)
     {
@@ -127,7 +152,7 @@ void JsonViewDlg::SortJsonByKey()
     }
     else
     {
-        if (CheckForTokenUndefined(JsonViewDlg::eMethod::SortJsonByKey, selectedText, res, NULL))
+        if (CheckForTokenUndefined(JsonViewDlg::eMethod::SortJsonByKey, selectedText.value(), res, NULL))
             return;
 
         ReportError(res);
@@ -199,6 +224,52 @@ bool JsonViewDlg::CheckForTokenUndefined(eMethod method, std::string selectedTex
     return false;
 }
 
+bool JsonViewDlg::IsMultiSelection(const ScintillaData &scintillaData) const
+{
+    std::string   text;
+    ScintillaCode code = ScintillaCode::Unknown;
+
+    ProcessScintillaData(scintillaData, text, code);
+
+    bool bRetVal = code == ScintillaCode::MultiLineSelection ? true : false;
+    return bRetVal;
+}
+
+auto JsonViewDlg::IsSelectionValidJson(const ScintillaData &scintillaData) const -> std::optional<std::string>
+{
+    std::string   text;
+    ScintillaCode code = ScintillaCode::Unknown;
+
+    ProcessScintillaData(scintillaData, text, code);
+
+    if (code == ScintillaCode::Success)
+        return text;
+
+    return std::nullopt;
+}
+
+void JsonViewDlg::ProcessScintillaData(const ScintillaData &scintillaData, std::string &text, ScintillaCode &code) const
+{
+    text.clear();
+    code = ScintillaCode::Unknown;
+
+    std::visit(
+        [&text, &code](auto &&arg)
+        {
+            using T = std::decay_t<decltype(arg)>;
+            if constexpr (std::is_same_v<T, std::string>)
+            {
+                text = arg;
+                code = ScintillaCode::Success;
+            }
+            else if constexpr (std::is_same_v<T, ScintillaCode>)
+            {
+                code = arg;
+            }
+        },
+        scintillaData);
+}
+
 void JsonViewDlg::HandleTabActivated()
 {
     const bool bIsVisible = isCreated() && isVisible();
@@ -223,10 +294,17 @@ void JsonViewDlg::HandleTabActivated()
 
 void JsonViewDlg::ValidateJson()
 {
-    // Get the current scintilla
-    const auto selectedText = m_pEditor->GetJsonText();
+    const auto selectedData  = m_pEditor->GetJsonText();
+    const auto selectedText = IsSelectionValidJson(selectedData);
+
+    if (!selectedText.has_value() || selectedText.value().empty())
+    {
+        const std::wstring msg = IsMultiSelection(selectedData) ? JSON_ERR_MULTI_SELECTION : JSON_ERR_PARSE;
+        ShowMessage(JSON_INFO_TITLE, msg, MB_OK | MB_ICONINFORMATION);
+        return;
+    }
 
-    Result res = JsonHandler(m_pSetting->parseOptions).ValidateJson(selectedText);
+    Result res = JsonHandler(m_pSetting->parseOptions).ValidateJson(selectedText.value());
 
     if (res.success)
     {
@@ -234,7 +312,7 @@ void JsonViewDlg::ValidateJson()
     }
     else
     {
-        if (CheckForTokenUndefined(JsonViewDlg::eMethod::ValidateJson, selectedText, res, NULL))
+        if (CheckForTokenUndefined(JsonViewDlg::eMethod::ValidateJson, selectedText.value(), res, NULL))
         {
             ShowMessage(JSON_INFO_TITLE, JSON_ERR_VALIDATE_SUCCESS, MB_OK | MB_ICONINFORMATION);
             return;
@@ -255,15 +333,21 @@ void JsonViewDlg::DrawJsonTree()
 
     // Refresh the view
     m_pEditor->RefreshViewHandle();
-    const std::string txtForParsing = m_pEditor->GetJsonText();
+    const auto selectedData  = m_pEditor->GetJsonText();
+    const auto selectedText = IsSelectionValidJson(selectedData);
 
-    if (txtForParsing.empty())
+    if (!selectedText.has_value() || selectedText.value().empty())
     {
         m_hTreeView->InsertNode(JSON_ERR_PARSE, NULL, rootNode);
+
+        if (IsMultiSelection(selectedData))
+        {
+            ShowMessage(JSON_INFO_TITLE, JSON_ERR_MULTI_SELECTION, MB_OK | MB_ICONINFORMATION);
+        }
     }
     else
     {
-        auto res = PopulateTreeUsingSax(rootNode, txtForParsing);
+        auto res = PopulateTreeUsingSax(rootNode, selectedText.value());
         if (res.has_value())
         {
             // This is the case when Notepad++ has JsonViewer Window opened for previous instance
diff --git a/src/NppJsonViewer/JsonViewDlg.h b/src/NppJsonViewer/JsonViewDlg.h
index 5f8fcd3..c21c129 100644
--- a/src/NppJsonViewer/JsonViewDlg.h
+++ b/src/NppJsonViewer/JsonViewDlg.h
@@ -84,6 +84,10 @@ class JsonViewDlg : public DockingDlgInterface
 
     bool CheckForTokenUndefined(eMethod method, std::string selectedText, Result &res, HTREEITEM tree_root);
 
+    bool IsMultiSelection(const ScintillaData &scintillaData) const;
+    auto IsSelectionValidJson(const ScintillaData &scintillaData) const -> std::optional<std::string>;
+    void ProcessScintillaData(const ScintillaData &scintillaData, std::string &text, ScintillaCode &code) const;
+
 protected:
     virtual INT_PTR CALLBACK run_dlgProc(UINT message, WPARAM wParam, LPARAM lParam) override;
 
diff --git a/src/NppJsonViewer/ScintillaEditor.cpp b/src/NppJsonViewer/ScintillaEditor.cpp
index c0502bc..141d299 100644
--- a/src/NppJsonViewer/ScintillaEditor.cpp
+++ b/src/NppJsonViewer/ScintillaEditor.cpp
@@ -17,10 +17,15 @@ void ScintillaEditor::RefreshViewHandle()
         m_hScintilla = (which == 0) ? m_NppData._scintillaMainHandle : m_NppData._scintillaSecondHandle;
 }
 
-auto ScintillaEditor::GetJsonText() -> std::string
+auto ScintillaEditor::GetJsonText() -> ScintillaData
 {
     if (!m_hScintilla)
-        return std::string();
+        return ScintillaCode::NotInitialized;
+
+    // Multi selection is not supported
+    size_t nSelections = ::SendMessage(m_hScintilla, SCI_GETSELECTIONS, 0, 0);
+    if (nSelections > 1)
+        return ScintillaCode::MultiLineSelection;
 
     // Adjust the selection position
     RefreshSelectionPos();
diff --git a/src/NppJsonViewer/ScintillaEditor.h b/src/NppJsonViewer/ScintillaEditor.h
index ac800bd..da60c80 100644
--- a/src/NppJsonViewer/ScintillaEditor.h
+++ b/src/NppJsonViewer/ScintillaEditor.h
@@ -2,6 +2,18 @@
 #include "Define.h"
 #include <string>
 #include <tuple>
+#include <variant>
+
+enum class ScintillaCode : short
+{
+    Unknown,
+    Success,
+    NotInitialized,
+    NoSelection,
+    MultiLineSelection
+};
+
+using ScintillaData = std::variant<std::string, ScintillaCode>;
 
 class ScintillaEditor
 {
@@ -10,7 +22,7 @@ class ScintillaEditor
     ~ScintillaEditor() = default;
 
     void RefreshViewHandle();
-    auto GetJsonText() -> std::string;
+    auto GetJsonText() -> ScintillaData;
     void SetLangAsJson() const;
     bool IsJsonFile() const;
     auto GetCurrentFileName() const -> std::wstring;