diff --git a/static/app.js b/static/app.js
index 9886583..ecc51c2 100644
--- a/static/app.js
+++ b/static/app.js
@@ -71,6 +71,7 @@ const defaultPrefs = {
   base_tf: '1m',
   enabled: { ma: { '1d': [10, 20, 50, 100, 200] }, drawings: true, manual: true, auto: false, horizontal: true, vwap: true, rth: true },
   hidden_levels_score: false,
+  hide_finer_trendlines: true,
 };
 
 // Stored preferences outlive the shape they were written in. Anything added to
@@ -1384,8 +1385,15 @@ createApp({
     function enabled(level) {
       if (level.kind === 'ma') return (prefs.value.enabled.ma[level.tf] || []).includes(level.period);
       if (level.kind === 'manual') {
-        return prefs.value.enabled.drawings && prefs.value.enabled.manual
-          && drawingVisible(level);
+        if (!(prefs.value.enabled.drawings && prefs.value.enabled.manual)) return false;
+        // Two independent hiding rules, so both apply: drawingVisible covers
+        // hideLowerTfDrawings, and hide_finer_trendlines hides sloped lines
+        // drawn on a finer timeframe than the one being viewed.
+        if (!drawingVisible(level)) return false;
+        if (prefs.value.hide_finer_trendlines && !ConfluenceChart.isFlat(level)) {
+          return timeframes.indexOf(level.tf) >= timeframes.indexOf(timeframe.value);
+        }
+        return true;
       }
       if (level.kind === 'horizontal') return prefs.value.enabled.horizontal;
       if (level.kind === 'vwap') return prefs.value.enabled.vwap;
diff --git a/static/index.html b/static/index.html
index d26bed5..cfe497c 100644
--- a/static/index.html
+++ b/static/index.html
@@ -78,6 +78,7 @@
           <label><input type="checkbox" v-model="autoScrollLivePrice"> Autoscroll to live price</label>
           <label><input type="checkbox" v-model="hideLowerTfDrawings"> Hide lower-TF drawings</label>
           <label><input type="checkbox" v-model="extraDetail"> Extra detail</label>
+          <label title="Daily and hourly trendlines still show on 1m; 1m trendlines stay off 1h and 1d"><input type="checkbox" v-model="prefs.hide_finer_trendlines"> Hide finer-timeframe trendlines</label>
         </details>
         <details class="sidebar-section tools-section" open>
           <summary>Tools</summary>