diff --git a/src/buffer/katetextbuffer.cpp b/src/buffer/katetextbuffer.cpp
--- a/src/buffer/katetextbuffer.cpp
+++ b/src/buffer/katetextbuffer.cpp
@@ -68,7 +68,7 @@
     , m_generateByteOrderMark(false)
     , m_endOfLineMode(eolUnix)
     , m_newLineAtEof(false)
-    , m_lineLengthLimit(4096)
+    , m_lineLengthLimit(100000)
     , m_alwaysUseKAuthForSave(alwaysUseKAuth)
 {
     // minimal block size must be > 0
diff --git a/src/document/katedocument.cpp b/src/document/katedocument.cpp
--- a/src/document/katedocument.cpp
+++ b/src/document/katedocument.cpp
@@ -2347,8 +2347,12 @@
         QPointer<KTextEditor::Message> message
             = new KTextEditor::Message(i18n("The file %1 was opened and contained lines longer than the configured Line Length Limit (%2 characters).<br />"
                                             "The longest of those lines was %3 characters long<br/>"
-                                            "Those lines were wrapped and the document is set to read-only mode, as saving will modify its content.",
-                                            this->url().toDisplayString(QUrl::PreferLocalFile), config()->lineLengthLimit(), m_buffer->longestLineLoaded()),
+                                            "Those lines were wrapped and the document is set to read-only mode, as saving will modify its content.<br />"
+                                            "<br /><b>Note:</b> Highlighting is <b>disabled</b> on a line after %4 characters, for performance reasons.",
+                                            this->url().toDisplayString(QUrl::PreferLocalFile),
+                                            config()->lineLengthLimit(),
+                                            m_buffer->longestLineLoaded(),
+                                            KateRenderer::maxHighlightLength()),
                                        KTextEditor::Message::Warning);
         QAction *increaseAndReload = new QAction(i18n("Temporarily raise limit and reload file"), message);
         connect(increaseAndReload, SIGNAL(triggered()), this, SLOT(openWithLineLengthLimitOverride()));
@@ -2363,6 +2367,19 @@
                                      "The longest of those lines was %3 characters long<br/>"
                                      "Those lines were wrapped and the document is set to read-only mode, as saving will modify its content.", this->url().toDisplayString(QUrl::PreferLocalFile), config()->lineLengthLimit(),m_buffer->longestLineLoaded());
     }
+    // warn long lines
+    else if (m_buffer->longestLineLoaded() > KateRenderer::maxHighlightLength()) {
+        QPointer<KTextEditor::Message> message
+        = new KTextEditor::Message(i18n("<b>Note:</b> Highlighting is <b>disabled</b> on a line after %1 characters, for performance reasons.",
+                                        KateRenderer::maxHighlightLength()), KTextEditor::Message::Information);
+        message->setWordWrap(true);
+        message->setPosition(KTextEditor::Message::TopInView);
+        message->setAutoHide(5000);
+        message->addAction(new QAction(i18n("Close"), message), true);
+
+        postMessage(message);
+    }
+
 
     //
     // return the success
diff --git a/src/render/katerenderer.h b/src/render/katerenderer.h
--- a/src/render/katerenderer.h
+++ b/src/render/katerenderer.h
@@ -277,12 +277,19 @@
      */
     bool isLineRightToLeft(KateLineLayoutPtr lineLayout) const;
 
+    /**
+     * This function returns the maximum length a line will be highlighted.
+     */
+    static int maxHighlightLength();
+
     /**
      * The ultimate decoration creation function.
      *
      * \param selectionsOnly return decorations for selections and/or dynamic highlighting.
      */
-    QVector<QTextLayout::FormatRange> decorationsForLine(const Kate::TextLine &textLine, int line, bool selectionsOnly = false, KateRenderRange *completionHighlight = nullptr, bool completionSelected = false) const;
+    QVector<QTextLayout::FormatRange> decorationsForLine(const Kate::TextLine &textLine, int line, bool selectionsOnly = false,
+                                                         KateRenderRange *completionHighlight = nullptr, bool completionSelected = false,
+                                                         int highlightLength = maxHighlightLength()) const;
 
     // Width calculators
     qreal spaceWidth() const;
diff --git a/src/render/katerenderer.cpp b/src/render/katerenderer.cpp
--- a/src/render/katerenderer.cpp
+++ b/src/render/katerenderer.cpp
@@ -380,7 +380,14 @@
     return false;
 }
 
-QVector<QTextLayout::FormatRange> KateRenderer::decorationsForLine(const Kate::TextLine &textLine, int line, bool selectionsOnly, KateRenderRange *completionHighlight, bool completionSelected) const
+int KateRenderer::maxHighlightLength()
+{
+    return 512;
+}
+
+QVector<QTextLayout::FormatRange> KateRenderer::decorationsForLine(const Kate::TextLine &textLine, int line, bool selectionsOnly,
+                                                                   KateRenderRange *completionHighlight, bool completionSelected,
+                                                                   int highlightLength) const
 {
     QVector<QTextLayout::FormatRange> newHighlight;
 
@@ -485,6 +492,9 @@
             endPosition = KTextEditor::Cursor(line + 1, 0);
         }
 
+        if (textLine->length() > highlightLength && !selectionsOnly) {
+            endPosition = KTextEditor::Cursor(line, maxHighlightLength());
+        }
         // Main iterative loop.  This walks through each set of highlighting ranges, and stops each
         // time the highlighting changes.  It then creates the corresponding QTextLayout::FormatRanges.
         while (currentPosition < endPosition) {
diff --git a/src/utils/kateconfig.cpp b/src/utils/kateconfig.cpp
--- a/src/utils/kateconfig.cpp
+++ b/src/utils/kateconfig.cpp
@@ -320,7 +320,7 @@
 const char KEY_SWAP_DIRECTORY[] = "Swap Directory";
 const char KEY_SWAP_SYNC_INTERVAL[] = "Swap Sync Interval";
 const char KEY_ON_THE_FLY_SPELLCHECK[] = "On-The-Fly Spellcheck";
-const char KEY_LINE_LENGTH_LIMIT[] = "Line Length Limit";
+const char KEY_LINE_LENGTH_LIMIT[] = "Line Length Limitation";
 }
 
 void KateDocumentConfig::readConfig(const KConfigGroup &config)
@@ -371,7 +371,7 @@
 
     setOnTheFlySpellCheck(config.readEntry(KEY_ON_THE_FLY_SPELLCHECK, false));
 
-    setLineLengthLimit(config.readEntry(KEY_LINE_LENGTH_LIMIT, 4096));
+    setLineLengthLimit(config.readEntry(KEY_LINE_LENGTH_LIMIT, 100000));
 
     configEnd();
 }
diff --git a/src/view/kateviewhelpers.cpp b/src/view/kateviewhelpers.cpp
--- a/src/view/kateviewhelpers.cpp
+++ b/src/view/kateviewhelpers.cpp
@@ -602,7 +602,7 @@
             const Kate::TextLine &kateline = m_doc->plainKateTextLine(realLineNumber);
 
             const QVector<Kate::TextLineData::Attribute> &attributes = kateline->attributesList();
-            QVector<QTextLayout::FormatRange> decorations = m_view->renderer()->decorationsForLine(kateline, realLineNumber);
+            QVector<QTextLayout::FormatRange> decorations = m_view->renderer()->decorationsForLine(kateline, realLineNumber, false, nullptr, false, s_lineWidth);
             int attributeIndex = 0;
 
             // Draw selection if it is on an empty line