diff --git a/Userland/Libraries/LibGUI/TextEditor.cpp b/Userland/Libraries/LibGUI/TextEditor.cpp
index d07504a9bb..29df2c4c68 100644
--- a/Userland/Libraries/LibGUI/TextEditor.cpp
+++ b/Userland/Libraries/LibGUI/TextEditor.cpp
@@ -290,6 +290,28 @@ void TextEditor::mousedown_event(MouseEvent& event)
         }
     }
 
+    if (gutter_content_rect(text_position.line()).contains(event.position())) {
+        auto& gutter_indicators = m_line_data[text_position.line()]->gutter_indicators;
+        auto indicator_position = 0;
+        for (auto i = 0u; i < m_gutter_indicators.size(); ++i) {
+            if ((gutter_indicators & (1 << i)) == 0)
+                continue;
+
+            if (gutter_indicator_rect(text_position.line(), indicator_position).contains(event.position())) {
+                auto& indicator_data = m_gutter_indicators[i];
+                if (indicator_data.on_click)
+                    indicator_data.on_click(text_position.line(), event.modifiers());
+                return;
+            }
+            indicator_position++;
+        }
+
+        // We didn't click on an indicator
+        if (on_gutter_click)
+            on_gutter_click(text_position.line(), event.modifiers());
+        return;
+    }
+
     if (on_mousedown)
         on_mousedown();
 
@@ -404,7 +426,7 @@ int TextEditor::gutter_width() const
 {
     if (!m_gutter_visible)
         return 0;
-    return line_height(); // square gutter
+    return line_height() * (m_most_gutter_indicators_displayed_on_one_line + 1);
 }
 
 Gfx::IntRect TextEditor::gutter_content_rect(size_t line_index) const
@@ -446,6 +468,18 @@ Gfx::IntRect TextEditor::folding_indicator_rect(size_t line_index) const
     };
 }
 
+Gfx::IntRect TextEditor::gutter_indicator_rect(size_t line_number, int indicator_position) const
+{
+    auto gutter_rect = gutter_content_rect(line_number);
+    auto indicator_size = gutter_rect.height();
+    return Gfx::IntRect {
+        gutter_rect.right() - static_cast<int>(lroundf(indicator_size * (indicator_position + 1.5f))),
+        gutter_rect.top(),
+        indicator_size,
+        indicator_size
+    };
+}
+
 Gfx::IntRect TextEditor::gutter_rect_in_inner_coordinates() const
 {
     return { 0, 0, gutter_width(), widget_inner_rect().height() };
@@ -599,6 +633,28 @@ void TextEditor::paint_event(PaintEvent& event)
         }
     }
 
+    // Draw gutter indicators
+    if (m_gutter_visible) {
+        for (size_t line_index = first_visible_line; line_index <= last_visible_line; ++line_index) {
+            if (!document().line_is_visible(line_index))
+                continue;
+
+            auto& gutter_indicators = m_line_data[line_index]->gutter_indicators;
+            if (gutter_indicators == 0)
+                continue;
+
+            auto indicator_position = 0;
+            for (auto i = 0u; i < m_gutter_indicators.size(); ++i) {
+                if ((gutter_indicators & (1 << i)) == 0)
+                    continue;
+
+                auto rect = gutter_indicator_rect(line_index, indicator_position);
+                m_gutter_indicators[i].draw_indicator(painter, rect, line_index);
+                indicator_position++;
+            }
+        }
+    }
+
     auto horizontal_scrollbar_value = horizontal_scrollbar().value();
     painter.translate(-horizontal_scrollbar_value, -vertical_scrollbar().value());
     if (m_icon && horizontal_scrollbar_value > 0)
@@ -2511,4 +2567,46 @@ void TextEditor::highlighter_did_set_folding_regions(Vector<GUI::TextDocumentFol
     recompute_all_visual_lines();
 }
 
+ErrorOr<TextEditor::GutterIndicatorID> TextEditor::register_gutter_indicator(PaintGutterIndicator draw_indicator, OnGutterIndicatorClick on_click)
+{
+    // We use a u32 to store a line's active gutter indicators, so that's the limit of how many we can have.
+    VERIFY(m_gutter_indicators.size() < 32);
+
+    GutterIndicatorID id = m_gutter_indicators.size();
+    TRY(m_gutter_indicators.try_empend(move(draw_indicator), move(on_click)));
+    return id;
+}
+
+void TextEditor::add_gutter_indicator(GutterIndicatorID id, size_t line)
+{
+    auto& line_indicators = m_line_data[line]->gutter_indicators;
+    if (line_indicators & (1 << id.value()))
+        return;
+    line_indicators |= (1 << id.value());
+
+    // Ensure the gutter is at least wide enough to display all the indicators on this line.
+    if (m_most_gutter_indicators_displayed_on_one_line < m_gutter_indicators.size()) {
+        unsigned indicators_on_line = popcount(line_indicators);
+        if (indicators_on_line > m_most_gutter_indicators_displayed_on_one_line) {
+            m_most_gutter_indicators_displayed_on_one_line = indicators_on_line;
+            update();
+        }
+    }
+
+    update(gutter_content_rect(line));
+}
+
+void TextEditor::remove_gutter_indicator(GutterIndicatorID id, size_t line)
+{
+    m_line_data[line]->gutter_indicators &= ~(1 << id.value());
+    update(gutter_content_rect(line));
+}
+
+void TextEditor::clear_gutter_indicators(GutterIndicatorID id)
+{
+    for (auto line = 0u; line < line_count(); ++line)
+        remove_gutter_indicator(id, line);
+    update();
+}
+
 }
diff --git a/Userland/Libraries/LibGUI/TextEditor.h b/Userland/Libraries/LibGUI/TextEditor.h
index dfaf80fa2f..dfabda73cb 100644
--- a/Userland/Libraries/LibGUI/TextEditor.h
+++ b/Userland/Libraries/LibGUI/TextEditor.h
@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include <AK/DistinctNumeric.h>
 #include <AK/Function.h>
 #include <LibCore/ElapsedTimer.h>
 #include <LibCore/Timer.h>
@@ -105,6 +106,15 @@ public:
     bool is_gutter_visible() const { return m_gutter_visible; }
     void set_gutter_visible(bool);
 
+    AK_TYPEDEF_DISTINCT_NUMERIC_GENERAL(size_t, GutterIndicatorID, CastToUnderlying, Comparison);
+    using PaintGutterIndicator = Function<void(Gfx::Painter&, Gfx::IntRect, size_t line)>;
+    using OnGutterIndicatorClick = Function<void(size_t line, unsigned modifiers)>;
+    ErrorOr<GutterIndicatorID> register_gutter_indicator(PaintGutterIndicator, OnGutterIndicatorClick = nullptr);
+    void add_gutter_indicator(GutterIndicatorID, size_t line);
+    void remove_gutter_indicator(GutterIndicatorID, size_t line);
+    void clear_gutter_indicators(GutterIndicatorID);
+    Gfx::IntRect gutter_indicator_rect(size_t line_number, int indicator_position) const;
+
     void set_icon(Gfx::Bitmap const*);
     Gfx::Bitmap const* icon() const { return m_icon; }
 
@@ -113,6 +123,7 @@ public:
     Function<void()> on_focusin;
     Function<void()> on_focusout;
     Function<void()> on_highlighter_change;
+    Function<void(size_t line, unsigned modifiers)> on_gutter_click;
 
     void set_text(StringView, AllowCallback = AllowCallback::Yes);
     void scroll_cursor_into_view();
@@ -400,6 +411,13 @@ private:
     int m_horizontal_content_padding { 3 };
     TextRange m_selection {};
 
+    struct GutterIndicator {
+        PaintGutterIndicator draw_indicator;
+        OnGutterIndicatorClick on_click;
+    };
+    Vector<GutterIndicator> m_gutter_indicators;
+    unsigned m_most_gutter_indicators_displayed_on_one_line { 0 };
+
     Optional<u32> m_substitution_code_point;
     mutable OwnPtr<Vector<u32>> m_substitution_string_data; // Used to avoid repeated String construction.
 
@@ -430,6 +448,7 @@ private:
     struct LineData {
         Vector<Utf32View> visual_lines;
         Gfx::IntRect visual_rect;
+        u32 gutter_indicators { 0 }; // A bitfield of which gutter indicators are present. (1 << GutterIndicatorID)
     };
 
     Vector<NonnullOwnPtr<LineData>> m_line_data;