diff --git a/gui/qt/datawidget.cpp b/gui/qt/datawidget.cpp
index 8c156cba9..ee9ebf6b5 100644
--- a/gui/qt/datawidget.cpp
+++ b/gui/qt/datawidget.cpp
@@ -6,6 +6,10 @@
 
 DataWidget::DataWidget(QWidget *parent) : QPlainTextEdit{parent} {
     moveable = false;
+    highlighter = new AsmHighlighter(document());
+    QFont font = this->font();
+    font.setStyleHint(QFont::TypeWriter);
+    setFont(font);
     setContextMenuPolicy(Qt::CustomContextMenu);
 }
 
@@ -15,6 +19,8 @@ void DataWidget::updateDarkMode() {
         selection.format.setBackground(selection.format.colorProperty(QTextFormat::UserProperty + darkMode));
     }
     updateAllHighlights();
+    delete highlighter;
+    highlighter = new AsmHighlighter(document());
 }
 
 void DataWidget::clearAllHighlights() {
@@ -25,6 +31,8 @@ void DataWidget::clearAllHighlights() {
 
     highlights.clear();
     updateAllHighlights();
+    delete highlighter;
+    highlighter = new AsmHighlighter(document());
 }
 
 void DataWidget::updateAllHighlights() {
@@ -118,3 +126,75 @@ void DataWidget::highlightCurrentLine() {
         }
     }
 }
+
+AsmHighlighter::AsmHighlighter(QTextDocument *parent) : QSyntaxHighlighter(parent) {
+    HighlightingRule rule;
+    bool darkMode = isRunningInDarkMode();
+
+    addressFormat.setForeground(QColor(darkMode ? "#888" : "#444"));
+    addressFormat.setFontWeight(QFont::Bold);
+
+    watchRFormat.setForeground(QColor("#008000"));
+    watchRFormat.setFontWeight(QFont::Bold);
+    watchWFormat.setForeground(QColor("#808000"));
+    watchWFormat.setFontWeight(QFont::Bold);
+    breakPFormat.setForeground(QColor("#800000"));
+    breakPFormat.setFontWeight(QFont::Bold);
+
+    mnemonicFormat.setForeground(QColor(darkMode ? "darkorange" : "darkblue"));
+
+    symbolFormat.setFontWeight(disasm.bold_sym ? QFont::DemiBold : QFont::Normal);
+    rule.pattern = QRegularExpression("\\b\\w+\\b");
+    rule.format = symbolFormat;
+    highlightingRules.append(rule);
+
+    decimalFormat.setForeground(QColor(darkMode ? "lime" : "green"));
+    rule.pattern = QRegularExpression("\\b\\d+\\b");
+    rule.format = decimalFormat;
+    highlightingRules.append(rule);
+
+    registerFormat.setForeground(QColor(darkMode ? "magenta" : "purple"));
+    rule.pattern = QRegularExpression("\\b([abcdehlirmpz]|af|bc|de|hl|sp|i[xy][hl]?|mb|n[cz]|p[eo])\\b", QRegularExpression::CaseInsensitiveOption);
+    rule.format = registerFormat;
+    highlightingRules.append(rule);
+
+    hexFormat.setForeground(QColor(darkMode ? "lime" : "green"));
+    rule.pattern = QRegularExpression("\\$[0-9a-fA-F]+\\b");
+    rule.format = hexFormat;
+    highlightingRules.append(rule);
+
+    parenFormat.setForeground(QColor(darkMode ? "lightblue" : "navy"));
+    rule.pattern = QRegularExpression("[()]");
+    rule.format = parenFormat;
+    highlightingRules.append(rule);
+
+    labelPattern = QRegularExpression(QStringLiteral("^(%1)\\s+(\\S+):")
+                                      .arg(disasm.addr ? QStringLiteral("[0-9a-fA-F]+") : QString()));
+    instructionPattern = QRegularExpression(QStringLiteral("^(%1) ([ R])([ W])([ X])\\s+(%2)\\s+(\\S+)")
+                                            .arg(disasm.addr ? QStringLiteral("[0-9a-fA-F]+") : QString(),
+                                                 disasm.bytes ? QStringLiteral("[0-9a-fA-F]+") : QStringLiteral(" ")));
+}
+
+void AsmHighlighter::highlightBlock(const QString &text) {
+    QRegularExpressionMatch match;
+    if ((match = labelPattern.match(text)).hasMatch()) {
+        setFormat(match.capturedStart(1), match.capturedLength(1), addressFormat);
+        setFormat(match.capturedStart(2), match.capturedLength(2), symbolFormat);
+    } else if ((match = instructionPattern.match(text)).hasMatch()) {
+        setFormat(match.capturedStart(1), match.capturedLength(1), addressFormat);
+        setFormat(match.capturedStart(2), match.capturedLength(2), watchRFormat);
+        setFormat(match.capturedStart(3), match.capturedLength(3), watchWFormat);
+        setFormat(match.capturedStart(4), match.capturedLength(4), breakPFormat);
+        setFormat(match.capturedStart(5), match.capturedLength(5), bytesFormat);
+        setFormat(match.capturedStart(6), match.capturedLength(6), mnemonicFormat);
+        foreach(const HighlightingRule &rule, highlightingRules) {
+            QRegularExpressionMatchIterator iter = rule.pattern.globalMatch(text, match.capturedEnd());
+            while (iter.hasNext()) {
+                const auto& innerMatch = iter.next();
+                if (innerMatch.hasMatch()) {
+                    setFormat(innerMatch.capturedStart(), innerMatch.capturedLength(), rule.format);
+                }
+            }
+        }
+    }
+}
diff --git a/gui/qt/datawidget.h b/gui/qt/datawidget.h
index eedc3f700..16d07e53d 100644
--- a/gui/qt/datawidget.h
+++ b/gui/qt/datawidget.h
@@ -2,6 +2,9 @@
 #define CODEEDITOR_H
 
 #include <QtWidgets/QPlainTextEdit>
+#include <QtGui/QSyntaxHighlighter>
+#include <QtGui/QTextCharFormat>
+#include <QtCore/QRegularExpression>
 #include <QtCore/QObject>
 
 QT_BEGIN_NAMESPACE
@@ -11,6 +14,40 @@ QT_BEGIN_NAMESPACE
     class QWidget;
 QT_END_NAMESPACE
 
+class AsmHighlighter : public QSyntaxHighlighter
+{
+    Q_OBJECT
+
+public:
+    AsmHighlighter(QTextDocument *parent = nullptr);
+
+protected:
+    void highlightBlock(const QString &text) Q_DECL_OVERRIDE;
+
+private:
+    struct HighlightingRule
+    {
+        QRegularExpression pattern;
+        QTextCharFormat format;
+    };
+    QVector<HighlightingRule> highlightingRules;
+
+    QTextCharFormat addressFormat;
+    QTextCharFormat symbolFormat;
+    QTextCharFormat watchRFormat;
+    QTextCharFormat watchWFormat;
+    QTextCharFormat breakPFormat;
+    QTextCharFormat bytesFormat;
+    QTextCharFormat mnemonicFormat;
+    QTextCharFormat hexFormat;
+    QTextCharFormat decimalFormat;
+    QTextCharFormat parenFormat;
+    QTextCharFormat registerFormat;
+
+    QRegularExpression labelPattern;
+    QRegularExpression instructionPattern;
+};
+
 class DataWidget : public QPlainTextEdit {
     Q_OBJECT
 
@@ -31,6 +68,7 @@ class DataWidget : public QPlainTextEdit {
 
 private:
     bool moveable;
+    AsmHighlighter *highlighter;
     QList<QTextEdit::ExtraSelection> highlights;
 };
 
diff --git a/gui/qt/debugger/disasm.cpp b/gui/qt/debugger/disasm.cpp
index 2ccf6f2a3..87c85fa89 100644
--- a/gui/qt/debugger/disasm.cpp
+++ b/gui/qt/debugger/disasm.cpp
@@ -23,11 +23,7 @@ static std::string strW(uint32_t data) {
     if (high) {
         range = disasm.map.equal_range(data);
         for (sit = range.first; sit != range.second; ++sit) {
-            if (disasm.bold_sym) {
-                ret += "<b>" + sit->second + "</b>";
-            } else {
-                ret += sit->second;
-            }
+            ret += sit->second;
             ret += '|';
         }
         if (!ret.empty()) {
@@ -37,11 +33,7 @@ static std::string strW(uint32_t data) {
         if (!disasm.il) {
             range = disasm.map.equal_range(cpu.registers.MBASE<<16|data);
             for (sit = range.first; sit != range.second; ++sit) {
-                if (disasm.bold_sym) {
-                    ret += "<b>" + sit->second + "</b>";
-                } else {
-                    ret += sit->second;
-                }
+                ret += sit->second;
                 ret += '|';
             }
             if (!ret.empty()) {
@@ -67,11 +59,7 @@ static std::string strA(uint32_t data) {
             if (!ret.empty()) {
                 ret += '|';
             }
-            if (disasm.bold_sym) {
-                ret += "<b>" + sit->second + "</b>";
-            } else {
-                ret += sit->second;
-            }
+            ret += sit->second;
         }
     }
     if (!ret.empty()) {
@@ -86,11 +74,7 @@ static std::string strA(uint32_t data) {
                 if (!ret.empty()) {
                     ret += '|';
                 }
-                if (disasm.bold_sym) {
-                    ret += "<b>" + sit->second + "</b>";
-                } else {
-                    ret += sit->second;
-                }
+                ret += sit->second;
             }
         }
         if (!ret.empty()) {
diff --git a/gui/qt/mainwindow.cpp b/gui/qt/mainwindow.cpp
index f8764cd5d..1996d3b40 100644
--- a/gui/qt/mainwindow.cpp
+++ b/gui/qt/mainwindow.cpp
@@ -886,7 +886,6 @@ void MainWindow::darkModeSwitch(bool darkMode) {
 #ifdef Q_OS_WIN
     QApplication::setStyle(darkMode ? "fusion" : "windowsvista");
 #endif
-    m_disasmOpcodeColor = darkMode ? "darkorange" : "darkblue";
     if (darkMode) {
         m_cBack.setColor(QPalette::Base, QColor(Qt::blue).lighter(180));
         m_cBack.setColor(QPalette::Text, Qt::black);
@@ -2389,15 +2388,14 @@ void MainWindow::disasmLine() {
 
         QString line;
         QString symbols;
-        QString highlighted;
 
         if (useLabel) {
             if (disasm.base > 511 || (disasm.base < 512 && sit->second[0] == '_')) {
-                line = QString(QStringLiteral("<pre><b><font color='#444'>%1</font></b>     %2</pre>"))
-                                        .arg(int2hex(static_cast<uint32_t>(disasm.base), 6),
-                                             QString::fromStdString(disasm.bold_sym ? "<b>" + sit->second + "</b>" : sit->second) + ":");
+                line = QStringLiteral("%1  %2:")
+                       .arg(disasm.addr ? int2hex(static_cast<uint32_t>(disasm.base), 6) : QString(),
+                            QString::fromStdString(sit->second));
 
-                m_disasm->appendHtml(line);
+                m_disasm->appendPlainText(line);
             }
 
             if (numLines == j + 1) {
@@ -2405,25 +2403,16 @@ void MainWindow::disasmLine() {
             }
             sit++;
         } else {
-            symbols = QString(QStringLiteral("<b><font color='#008000'>%1</font><font color='#808000'>%2</font><font color='#800000'>%3</font></b>"))
-                             .arg((disasm.highlight.watchR  ? QStringLiteral("R") : QStringLiteral(" ")),
-                                  (disasm.highlight.watchW ? QStringLiteral("W") : QStringLiteral(" ")),
-                                  (disasm.highlight.breakP  ? QStringLiteral("X") : QStringLiteral(" ")));
-
-            highlighted = QString::fromStdString(disasm.instr.operands)
-                                  .replace(QRegularExpression(QStringLiteral("(\\$[0-9a-fA-F]+)")), QStringLiteral("<font color='green'>\\1</font>")) // hex numbers
-                                  .replace(QRegularExpression(QStringLiteral("(^\\d)")), QStringLiteral("<font color='blue'>\\1</font>"))             // dec number
-                                  .replace(QRegularExpression(QStringLiteral("([()])")), QStringLiteral("<font color='#600'>\\1</font>"));            // parentheses
-
-            line = QString(QStringLiteral("<pre><b><font color='#444'>%1</font></b> %2 %3  <font color='%4'>%5</font> %6</pre>"))
+            line = QString(QStringLiteral("%1 %2%3%4 %5  %6 %7"))
                            .arg(disasm.addr ? int2hex(static_cast<uint32_t>(disasm.base), 6) : QString(),
-                                symbols,
+                                disasm.highlight.watchR ? QStringLiteral("R") : QStringLiteral(" "),
+                                disasm.highlight.watchW ? QStringLiteral("W") : QStringLiteral(" "),
+                                disasm.highlight.breakP ? QStringLiteral("X") : QStringLiteral(" "),
                                 disasm.bytes ? QString::fromStdString(disasm.instr.data).leftJustified(12, ' ') : QStringLiteral(" "),
-                                m_disasmOpcodeColor,
                                 QString::fromStdString(disasm.instr.opcode),
-                                highlighted);
+                                QString::fromStdString(disasm.instr.operands));
 
-            m_disasm->appendHtml(line);
+            m_disasm->appendPlainText(line);
         }
     }
 
diff --git a/gui/qt/mainwindow.h b/gui/qt/mainwindow.h
index 7350c641f..d8016e167 100644
--- a/gui/qt/mainwindow.h
+++ b/gui/qt/mainwindow.h
@@ -573,7 +573,6 @@ class MainWindow : public QMainWindow {
     InterCom com;
 
     bool m_isInDarkMode = false;
-    const char* m_disasmOpcodeColor;
 
     int m_watchGUIMask = DBG_MASK_NONE;