diff --git a/Source/WebInspectorUI/ChangeLog b/Source/WebInspectorUI/ChangeLog
index 01bd1b4..4c3992d 100644
--- a/Source/WebInspectorUI/ChangeLog
+++ b/Source/WebInspectorUI/ChangeLog
@@ -1,3 +1,26 @@
+2020-04-01  Nikita Vasilyev  <nvasilyev@apple.com>
+
+        Web Inspector: Use ECMAScript Numeric Separators for numbers with 5 or more digits
+        https://bugs.webkit.org/show_bug.cgi?id=209879
+
+        Reviewed by Joseph Pecoraro.
+
+        Instead of `1000000` write `1_000_000` so it's easier to read.
+
+        * UserInterface/Base/Utilities.js:
+        * UserInterface/Controllers/JavaScriptLogViewController.js:
+        * UserInterface/Controllers/TimelineManager.js:
+        * UserInterface/Models/Gradient.js:
+        (WI.Gradient.prototype.stringFromStops):
+        * UserInterface/Models/HeapAllocationsInstrument.js:
+        (WI.HeapAllocationsInstrument.prototype.startInstrumentation):
+        * UserInterface/Protocol/Connection.js:
+        (InspectorBackend.Connection.prototype._dispatchResponse):
+        * UserInterface/Views/Layers3DContentView.js:
+        (WI.Layers3DContentView.prototype.initialLayout):
+        * UserInterface/Views/NetworkTableContentView.js:
+        (WI.NetworkTableContentView.prototype._updateLoadTimeStatistic):
+
 2020-03-31  Jon Davis  <jond@apple.com>
 
         Added new WebSocket icon
diff --git a/Source/WebInspectorUI/UserInterface/Base/Utilities.js b/Source/WebInspectorUI/UserInterface/Base/Utilities.js
index 0459622..f81aee6 100644
--- a/Source/WebInspectorUI/UserInterface/Base/Utilities.js
+++ b/Source/WebInspectorUI/UserInterface/Base/Utilities.js
@@ -1348,13 +1348,13 @@
         if (num < 1000)
             return num.toLocaleString();
 
-        if (num < 1000000)
+        if (num < 1_000_000)
             return WI.UIString("%.1fK").format(Math.round(num / 100) / 10);
 
-        if (num < 1000000000)
-            return WI.UIString("%.1fM").format(Math.round(num / 100000) / 10);
+        if (num < 1_000_000_000)
+            return WI.UIString("%.1fM").format(Math.round(num / 100_000) / 10);
 
-        return WI.UIString("%.1fB").format(Math.round(num / 100000000) / 10);
+        return WI.UIString("%.1fB").format(Math.round(num / 100_000_000) / 10);
     }
 });
 
diff --git a/Source/WebInspectorUI/UserInterface/Controllers/JavaScriptLogViewController.js b/Source/WebInspectorUI/UserInterface/Controllers/JavaScriptLogViewController.js
index 105f21c..772b6fe 100644
--- a/Source/WebInspectorUI/UserInterface/Controllers/JavaScriptLogViewController.js
+++ b/Source/WebInspectorUI/UserInterface/Controllers/JavaScriptLogViewController.js
@@ -362,5 +362,5 @@
     }
 };
 
-WI.JavaScriptLogViewController.CachedPropertiesDuration = 30000;
+WI.JavaScriptLogViewController.CachedPropertiesDuration = 30_000;
 WI.JavaScriptLogViewController.IgnoredRepeatCount = Symbol("ignored-repeat-count");
diff --git a/Source/WebInspectorUI/UserInterface/Controllers/TimelineManager.js b/Source/WebInspectorUI/UserInterface/Controllers/TimelineManager.js
index 729696f..fd1c442 100644
--- a/Source/WebInspectorUI/UserInterface/Controllers/TimelineManager.js
+++ b/Source/WebInspectorUI/UserInterface/Controllers/TimelineManager.js
@@ -1440,6 +1440,6 @@
     RecordingImported: "timeline-manager-recording-imported",
 };
 
-WI.TimelineManager.MaximumAutoRecordDuration = 90000; // 90 seconds
-WI.TimelineManager.MaximumAutoRecordDurationAfterLoadEvent = 10000; // 10 seconds
-WI.TimelineManager.DeadTimeRequiredToStopAutoRecordingEarly = 2000; // 2 seconds
+WI.TimelineManager.MaximumAutoRecordDuration = 90_000; // 90 seconds
+WI.TimelineManager.MaximumAutoRecordDurationAfterLoadEvent = 10_000; // 10 seconds
+WI.TimelineManager.DeadTimeRequiredToStopAutoRecordingEarly = 2_000; // 2 seconds
diff --git a/Source/WebInspectorUI/UserInterface/Models/Gradient.js b/Source/WebInspectorUI/UserInterface/Models/Gradient.js
index df89c16..f73de75 100644
--- a/Source/WebInspectorUI/UserInterface/Models/Gradient.js
+++ b/Source/WebInspectorUI/UserInterface/Models/Gradient.js
@@ -142,7 +142,7 @@
         return stops.map(function(stop, index) {
             var str = stop.color;
             if (stop.offset !== index / count)
-                str += " " + Math.round(stop.offset * 10000) / 100 + "%";
+                str += " " + Math.round(stop.offset * 10_000) / 100 + "%";
             return str;
         }).join(", ");
     }
diff --git a/Source/WebInspectorUI/UserInterface/Models/HeapAllocationsInstrument.js b/Source/WebInspectorUI/UserInterface/Models/HeapAllocationsInstrument.js
index 13b08d2..6a68133 100644
--- a/Source/WebInspectorUI/UserInterface/Models/HeapAllocationsInstrument.js
+++ b/Source/WebInspectorUI/UserInterface/Models/HeapAllocationsInstrument.js
@@ -60,7 +60,7 @@
         }
 
         // Periodic snapshots.
-        const snapshotInterval = 10000;
+        const snapshotInterval = 10_000;
         this._snapshotIntervalIdentifier = setInterval(this._takeHeapSnapshot.bind(this), snapshotInterval);
     }
 
diff --git a/Source/WebInspectorUI/UserInterface/Protocol/Connection.js b/Source/WebInspectorUI/UserInterface/Protocol/Connection.js
index 1ba5c99..302cdba 100644
--- a/Source/WebInspectorUI/UserInterface/Protocol/Connection.js
+++ b/Source/WebInspectorUI/UserInterface/Protocol/Connection.js
@@ -102,7 +102,7 @@
     {
         console.assert(this._pendingResponses.size >= 0);
 
-        if (messageObject.error && messageObject.error.code !== -32000)
+        if (messageObject.error && messageObject.error.code !== -32_000)
             console.error("Request with id = " + messageObject["id"] + " failed. " + JSON.stringify(messageObject.error));
 
         let sequenceId = messageObject["id"];
diff --git a/Source/WebInspectorUI/UserInterface/Views/Layers3DContentView.js b/Source/WebInspectorUI/UserInterface/Views/Layers3DContentView.js
index 61bc36d..1b273d6 100644
--- a/Source/WebInspectorUI/UserInterface/Views/Layers3DContentView.js
+++ b/Source/WebInspectorUI/UserInterface/Views/Layers3DContentView.js
@@ -163,7 +163,7 @@
         window.matchMedia("(prefers-color-scheme: dark)").addListener(updateBackground);
         updateBackground();
 
-        this._camera = new THREE.PerspectiveCamera(45, this.element.offsetWidth / this.element.offsetHeight, 1, 100000);
+        this._camera = new THREE.PerspectiveCamera(45, this.element.offsetWidth / this.element.offsetHeight, 1, 100_000);
 
         this._controls = new THREE.OrbitControls(this._camera, this._renderer.domElement);
         this._controls.enableDamping = true;
diff --git a/Source/WebInspectorUI/UserInterface/Views/NetworkTableContentView.js b/Source/WebInspectorUI/UserInterface/Views/NetworkTableContentView.js
index 906c94f..f7c20bc 100644
--- a/Source/WebInspectorUI/UserInterface/Views/NetworkTableContentView.js
+++ b/Source/WebInspectorUI/UserInterface/Views/NetworkTableContentView.js
@@ -2167,12 +2167,12 @@
         let duration = Date.now() - loadTimeStatistic.start;
 
         let delay = loadTimeStatistic.delay;
-        if (duration >= 1000) // 1 second
+        if (duration >= 1_000) // 1 second
             delay = 100;
-        else if (duration >= 60000) // 60 seconds
-            delay = 1000;
-        else if (duration >= 3600000) // 1 minute
-            delay = 10000;
+        else if (duration >= 60_000) // 60 seconds
+            delay = 1_000;
+        else if (duration >= 3_600_000) // 1 minute
+            delay = 10_000;
 
         if (delay !== loadTimeStatistic.delay) {
             loadTimeStatistic.delay = delay;
@@ -2189,7 +2189,7 @@
             loadTimeStatistic.container.hidden = !this._isShowingMainCollection();
 
         if (isNaN(mainFrameStartTime) || isNaN(mainFrameLoadEventTime)) {
-            this._updateStatistic("load-time", WI.UIString("Loading for %s"), Number.secondsToString(duration / 1000));
+            this._updateStatistic("load-time", WI.UIString("Loading for %s"), Number.secondsToString(duration / 1_000));
             return;
         }