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
@@ -2308,8 +2308,12 @@
         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 />Note: Highlighting for lines longer than %4 characters is disabled 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()));
@@ -2324,6 +2328,16 @@
                                      "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("The file %1 contains lines longer than %2 characters.<br />"
+        "<br />Note: Highlighting for lines longer than %2 characters is disabled for performance reasons.",
+        this->url().toDisplayString(QUrl::PreferLocalFile), KateRenderer::maxHighlightLength()), KTextEditor::Message::Information);
+        message->setWordWrap(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
@@ -365,6 +365,11 @@
     KTextEditor::Attribute::Ptr attribute(uint pos) const;
     KTextEditor::Attribute::Ptr specificAttribute(int context) const;
 
+    /**
+     * This constant is the maximum length a line can have and still be highlighted.
+     */
+    inline static int maxHighlightLength() { return 1024; }
+
 private:
     /**
      * Paint a trailing space on position (x, y).
diff --git a/src/render/katerenderer.cpp b/src/render/katerenderer.cpp
--- a/src/render/katerenderer.cpp
+++ b/src/render/katerenderer.cpp
@@ -384,19 +384,26 @@
 {
     QVector<QTextLayout::FormatRange> newHighlight;
 
+    if (textLine->length() > maxHighlightLength() && !selectionsOnly) {
+        return newHighlight;
+    }
+
     // Don't compute the highlighting if there isn't going to be any highlighting
     QList<Kate::TextRange *> rangesWithAttributes = m_doc->buffer().rangesForLine(line, m_printerFriendly ? nullptr : m_view, true);
     if (selectionsOnly || !textLine->attributesList().isEmpty() || !rangesWithAttributes.isEmpty()) {
         RenderRangeList renderRanges;
 
-        // Add the inbuilt highlighting to the list
-        NormalRenderRange *inbuiltHighlight = new NormalRenderRange();
-        const QVector<Kate::TextLineData::Attribute> &al = textLine->attributesList();
-        for (int i = 0; i < al.count(); ++i)
-            if (al[i].length > 0 && al[i].attributeValue > 0) {
-                inbuiltHighlight->addRange(new KTextEditor::Range(KTextEditor::Cursor(line, al[i].offset), al[i].length), specificAttribute(al[i].attributeValue));
+        if (textLine->length() <= maxHighlightLength()) {
+            // Add the inbuilt highlighting to the list
+            NormalRenderRange *inbuiltHighlight = new NormalRenderRange();
+            const QVector<Kate::TextLineData::Attribute> &al = textLine->attributesList();
+            for (int i = 0; i < al.count(); ++i) {
+                if (al[i].length > 0 && al[i].attributeValue > 0) {
+                    inbuiltHighlight->addRange(new KTextEditor::Range(KTextEditor::Cursor(line, al[i].offset), al[i].length), specificAttribute(al[i].attributeValue));
+                }
             }
-        renderRanges.append(inbuiltHighlight);
+            renderRanges.append(inbuiltHighlight);
+        }
 
         if (!completionHighlight) {
             // check for dynamic hl stuff