--- a/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_console_dir.js
+++ b/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_console_dir.js
@@ -34,17 +34,17 @@ add_task(async function() {
     });
     arrayOiNodes = arrayOi.querySelectorAll(".node");
   }
 
   // There are 6 nodes: the root, 1, 2, {a: "a", b: "b"}, length and the proto.
   is(arrayOiNodes.length, 6, "There is the expected number of nodes in the tree");
   let propertiesNodes = [...arrayOi.querySelectorAll(".object-label")]
     .map(el => el.textContent);
-  const arrayPropertiesNames = ["0", "1", "2", "length", "__proto__"];
+  const arrayPropertiesNames = ["0", "1", "2", "length", "<prototype>"];
   is(JSON.stringify(propertiesNodes), JSON.stringify(arrayPropertiesNames));
 
   info("console.dir on a long object");
   const obj = Array.from({length: 100}).reduce((res, _, i) => {
     res["item-" + (i + 1).toString().padStart(3, "0")] = i + 1;
     return res;
   }, {});
   await ContentTask.spawn(gBrowser.selectedBrowser, obj, function(data) {
@@ -62,17 +62,17 @@ add_task(async function() {
       childList: true
     });
     objectOiNodes = objectOi.querySelectorAll(".node");
   }
 
   // There are 102 nodes: the root, 100 "item-N" properties, and the proto.
   is(objectOiNodes.length, 102, "There is the expected number of nodes in the tree");
   const objectPropertiesNames = Object.getOwnPropertyNames(obj).map(name => `"${name}"`);
-  objectPropertiesNames.push("__proto__");
+  objectPropertiesNames.push("<prototype>");
   propertiesNodes = [...objectOi.querySelectorAll(".object-label")]
     .map(el => el.textContent);
   is(JSON.stringify(propertiesNodes), JSON.stringify(objectPropertiesNames));
 });
 
 function findConsoleDir(node, index) {
   return node.querySelectorAll(".dir.message")[index];
 }

--- a/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_inspect_cross_domain_object.js
+++ b/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_inspect_cross_domain_object.js
@@ -31,17 +31,17 @@ add_task(async function() {
 
   info("Expanding the first object inspector");
   await expandObjectInspector(oi1);
 
   // The first object inspector now looks like:
   // ▼ {…}
   // |  bug: 869003
   // |  hello: "world!"
-  // |  ▶︎ __proto__: Object { … }
+  // |  ▶︎ <prototype>: Object { … }
 
   let oi1Nodes = oi1.querySelectorAll(".node");
   is(oi1Nodes.length, 4, "There is the expected number of nodes in the tree");
   ok(oi1.textContent.includes("bug: 869003"), "Expected content");
   ok(oi1.textContent.includes('hello: "world!"'), "Expected content");
 
   info("Expanding the second object inspector");
   await expandObjectInspector(oi2);
@@ -50,17 +50,17 @@ add_task(async function() {
   // ▼ func()
   // |  arguments: null
   // |  bug: 869003
   // |  caller: null
   // |  hello: "world!"
   // |  length: 1
   // |  name: "func"
   // |  ▶︎ prototype: Object { … }
-  // |  ▶︎ __proto__: function ()
+  // |  ▶︎ <prototype>: function ()
 
   let oi2Nodes = oi2.querySelectorAll(".node");
   is(oi2Nodes.length, 9, "There is the expected number of nodes in the tree");
   ok(oi2.textContent.includes("arguments: null"), "Expected content");
   ok(oi2.textContent.includes("bug: 869003"), "Expected content");
   ok(oi2.textContent.includes("caller: null"), "Expected content");
   ok(oi2.textContent.includes('hello: "world!"'), "Expected content");
   ok(oi2.textContent.includes("length: 1"), "Expected content");

--- a/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_object_in_sidebar.js
+++ b/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_object_in_sidebar.js
@@ -36,17 +36,17 @@ add_task(async function() {
     });
     oiNodes = objectInspector.querySelectorAll(".node");
   }
 
   // There are 5 nodes: the root, a, b, c, and proto.
   is(oiNodes.length, 5, "There is the expected number of nodes in the tree");
   let propertiesNodes = [...objectInspector.querySelectorAll(".object-label")]
     .map(el => el.textContent);
-  const arrayPropertiesNames = ["a", "b", "c", "__proto__"];
+  const arrayPropertiesNames = ["a", "b", "c", "<prototype>"];
   is(JSON.stringify(propertiesNodes), JSON.stringify(arrayPropertiesNames));
 });
 
 async function showSidebarWithContextMenu(hud, node, expectMutation) {
   let wrapper = hud.ui.document.querySelector(".webconsole-output-wrapper");
   let onSidebarShown = waitForNodeMutation(wrapper, { childList: true });
 
   let contextMenu = await openContextMenu(hud, node);

--- a/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_object_inspector.js
+++ b/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_object_inspector.js
@@ -43,17 +43,17 @@ add_task(async function() {
   let arrayOiNodes = arrayOi.querySelectorAll(".node");
 
   // The object inspector now looks like:
   // ▼ […]
   // |  0: 1
   // |  1: 2
   // |  ▶︎ 2: {a: "a", b: "b"}
   // |  length: 3
-  // |  ▶︎ __proto__
+  // |  ▶︎ <prototype>
   is(arrayOiNodes.length, 6, "There is the expected number of nodes in the tree");
 
   info("Expanding a leaf of the array object inspector");
   let arrayOiNestedObject = arrayOiNodes[3];
   onArrayOiMutation = waitForNodeMutation(arrayOi, {
     childList: true
   });
 
@@ -67,19 +67,19 @@ add_task(async function() {
 
   // The object inspector now looks like:
   // ▼ […]
   // |  0: 1
   // |  1: 2
   // |  ▼ 2: {…}
   // |  |  a: "a"
   // |  |  b: "b"
-  // |  |  ▶︎ __proto__
+  // |  |  ▶︎ <prototype>
   // |  length: 3
-  // |  ▶︎ __proto__
+  // |  ▶︎ <prototype>
   is(arrayOiNodes.length, 9, "There is the expected number of nodes in the tree");
 
   info("Collapsing the root");
   onArrayOiMutation = waitForNodeMutation(arrayOi, {
     childList: true
   });
   arrayOi.querySelector(".arrow").click();
 
@@ -116,11 +116,11 @@ add_task(async function() {
     "The arrow of the root node of the tree is expanded after clicking on it");
 
   let objectOiNodes = objectOi.querySelectorAll(".node");
   // The object inspector now looks like:
   // ▼ {…}
   // |  c: "c"
   // |  ▶︎ d: [3, 4]
   // |  length: 987
-  // |  ▶︎ __proto__
+  // |  ▶︎ <prototype>
   is(objectOiNodes.length, 5, "There is the expected number of nodes in the tree");
 });

--- a/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_object_inspector_while_debugging_and_inspecting.js
+++ b/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_object_inspector_while_debugging_and_inspecting.js
@@ -50,24 +50,24 @@ add_task(async function() {
   await onOiExpanded;
 
   ok(oi.querySelector(".arrow").classList.contains("expanded"),
     "Object inspector expanded");
 
   // The object inspector now looks like:
   // {...}
   // |  testProp2: "testValue2"
-  // |  __proto__: Object { ... }
+  // |  <prototype>: Object { ... }
 
   let oiNodes = oi.querySelectorAll(".node");
   is(oiNodes.length, 3, "There is the expected number of nodes in the tree");
 
   ok(oiNodes[0].textContent.includes(`{\u2026}`));
   ok(oiNodes[1].textContent.includes(`testProp2: "testValue2"`));
-  ok(oiNodes[2].textContent.includes(`__proto__: Object { \u2026 }`));
+  ok(oiNodes[2].textContent.includes(`<prototype>: Object { \u2026 }`));
 });
 
 async function waitForFrameAdded() {
   let target = TargetFactory.forTab(gBrowser.selectedTab);
   let toolbox = gDevTools.getToolbox(target);
   let thread = toolbox.threadClient;
 
   info("Waiting for framesadded");