diff --git a/browser/app/profile/firefox.js b/browser/app/profile/firefox.js
index 5912c1b52079..014974bf6f44 100644
--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -1344,7 +1344,7 @@ pref("devtools.toolbox.sidebar.width", 500);
 pref("devtools.toolbox.host", "bottom");
 pref("devtools.toolbox.previousHost", "side");
 pref("devtools.toolbox.selectedTool", "webconsole");
-pref("devtools.toolbox.toolbarSpec", '["splitconsole", "paintflashing toggle","tilt toggle","scratchpad","resize toggle","eyedropper","screenshot --fullpage", "rulers"]');
+pref("devtools.toolbox.toolbarSpec", '["splitconsole", "paintflashing toggle","tilt toggle","scratchpad","resize toggle","eyedropper","screenshot --fullpage", "rulers", "measure"]');
 pref("devtools.toolbox.sideEnabled", true);
 pref("devtools.toolbox.zoomValue", "1");
 pref("devtools.toolbox.splitconsoleEnabled", false);
@@ -1361,6 +1361,7 @@ pref("devtools.command-button-responsive.enabled", true);
 pref("devtools.command-button-eyedropper.enabled", false);
 pref("devtools.command-button-screenshot.enabled", false);
 pref("devtools.command-button-rulers.enabled", false);
+pref("devtools.command-button-measure.enabled", false);
 
 // Inspector preferences
 // Enable the Inspector
diff --git a/devtools/client/commandline/test/browser.ini b/devtools/client/commandline/test/browser.ini
index 9e9832c386a9..ed26456dc9c1 100644
--- a/devtools/client/commandline/test/browser.ini
+++ b/devtools/client/commandline/test/browser.ini
@@ -64,6 +64,7 @@ support-files =
 support-files =
   browser_cmd_jsb_script.jsi
 [browser_cmd_listen.js]
+[browser_cmd_measure.js]
 [browser_cmd_media.js]
 support-files =
   browser_cmd_media.html
diff --git a/devtools/client/commandline/test/browser_cmd_measure.js b/devtools/client/commandline/test/browser_cmd_measure.js
new file mode 100644
index 000000000000..7dd9bd9c9acb
--- /dev/null
+++ b/devtools/client/commandline/test/browser_cmd_measure.js
@@ -0,0 +1,53 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Tests the highlight command, ensure no invalid arguments are given
+
+const TEST_PAGE = "data:text/html;charset=utf-8,foo";
+
+function test() {
+  return Task.spawn(spawnTest).then(finish, helpers.handleError);
+}
+
+function* spawnTest() {
+  let options = yield helpers.openTab(TEST_PAGE);
+  yield helpers.openToolbar(options);
+
+  yield helpers.audit(options, [
+    {
+      setup: "measure",
+      check: {
+        input: "measure",
+        markup: "VVVVVVV",
+        status: "VALID"
+      }
+    },
+    {
+      setup: "measure on",
+      check: {
+        input: "measure on",
+        markup: "VVVVVVVVEE",
+        status: "ERROR"
+      },
+      exec: {
+        output: "Error: Too many arguments"
+      }
+    },
+    {
+      setup: "measure --visible",
+      check: {
+        input: "measure --visible",
+        markup: "VVVVVVVVEEEEEEEEE",
+        status: "ERROR"
+      },
+      exec: {
+        output: "Error: Too many arguments"
+      }
+    }
+  ]);
+
+  yield helpers.closeToolbar(options);
+  yield helpers.closeTab(options);
+}
diff --git a/devtools/client/framework/toolbox.js b/devtools/client/framework/toolbox.js
index 7f9c1f7d78b7..453367938b6d 100644
--- a/devtools/client/framework/toolbox.js
+++ b/devtools/client/framework/toolbox.js
@@ -92,7 +92,8 @@ const ToolboxButtons = exports.ToolboxButtons = [
   { id: "command-button-scratchpad" },
   { id: "command-button-eyedropper" },
   { id: "command-button-screenshot" },
-  { id: "command-button-rulers"}
+  { id: "command-button-rulers" },
+  { id: "command-button-measure" }
 ];
 
 /**
diff --git a/devtools/client/inspector/test/browser.ini b/devtools/client/inspector/test/browser.ini
index 5a0585fc3bc3..146045654ce4 100644
--- a/devtools/client/inspector/test/browser.ini
+++ b/devtools/client/inspector/test/browser.ini
@@ -63,6 +63,8 @@ skip-if = e10s # GCLI isn't e10s compatible. See bug 1128988.
 [browser_inspector_highlighter-keybinding_02.js]
 [browser_inspector_highlighter-keybinding_03.js]
 [browser_inspector_highlighter-keybinding_04.js]
+[browser_inspector_highlighter-measure_01.js]
+[browser_inspector_highlighter-measure_02.js]
 [browser_inspector_highlighter-options.js]
 [browser_inspector_highlighter-rect_01.js]
 [browser_inspector_highlighter-rect_02.js]
diff --git a/devtools/client/inspector/test/browser_inspector_highlighter-measure_01.js b/devtools/client/inspector/test/browser_inspector_highlighter-measure_01.js
new file mode 100644
index 000000000000..5a398b47925d
--- /dev/null
+++ b/devtools/client/inspector/test/browser_inspector_highlighter-measure_01.js
@@ -0,0 +1,88 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const TEST_URL = `data:text/html;charset=utf-8,
+                    <div style='
+                        position:absolute;
+                        left: 0;
+                        top: 0;
+                        width: 40000px;
+                        height: 8000px'>
+                    </div>`;
+
+const PREFIX = "measuring-tool-highlighter-";
+const HIGHLIGHTER_TYPE = "MeasuringToolHighlighter";
+
+const X = 32;
+const Y = 20;
+
+add_task(function*() {
+  let helper = yield openInspectorForURL(TEST_URL)
+                       .then(getHighlighterHelperFor(HIGHLIGHTER_TYPE));
+
+  let { finalize } = helper;
+
+  helper.prefix = PREFIX;
+
+  yield isHiddenByDefault(helper);
+  yield areLabelsHiddenByDefaultWhenShows(helper);
+  yield areLabelsProperlyDisplayedWhenMouseMoved(helper);
+
+  yield finalize();
+});
+
+function* isHiddenByDefault({isElementHidden}) {
+  info("Checking the highlighter is hidden by default");
+
+  let hidden = yield isElementHidden("elements");
+  ok(hidden, "highlighter's root is hidden by default");
+
+  hidden = yield isElementHidden("label-size");
+  ok(hidden, "highlighter's label size is hidden by default");
+
+  hidden = yield isElementHidden("label-position");
+  ok(hidden, "highlighter's label position is hidden by default");
+}
+
+function* areLabelsHiddenByDefaultWhenShows({isElementHidden, show}) {
+  info("Checking the highlighter is displayed when asked");
+
+  yield show();
+
+  let hidden = yield isElementHidden("elements");
+  is(hidden, false, "highlighter is visible after show");
+
+  hidden = yield isElementHidden("label-size");
+  ok(hidden, "label's size still hidden");
+
+  hidden = yield isElementHidden("label-position");
+  ok(hidden, "label's position still hidden");
+}
+
+function* areLabelsProperlyDisplayedWhenMouseMoved({isElementHidden,
+  synthesizeMouse, getElementTextContent}) {
+  info("Checking labels are properly displayed when mouse moved");
+
+  yield synthesizeMouse({
+    selector: ":root",
+    options: {type: "mousemove"},
+    x: X,
+    y: Y
+  });
+
+  let hidden = yield isElementHidden("label-position");
+  is(hidden, false, "label's position is displayed after the mouse is moved");
+
+  hidden = yield isElementHidden("label-size");
+  ok(hidden, "label's size still hidden");
+
+  let text = yield getElementTextContent("label-position");
+
+  let [x, y] = text.replace(/ /g, "").split(/\n/);
+
+  is(+x, X, "label's position shows the proper X coord");
+  is(+y, Y, "label's position shows the proper Y coord");
+}
diff --git a/devtools/client/inspector/test/browser_inspector_highlighter-measure_02.js b/devtools/client/inspector/test/browser_inspector_highlighter-measure_02.js
new file mode 100644
index 000000000000..ff8536384543
--- /dev/null
+++ b/devtools/client/inspector/test/browser_inspector_highlighter-measure_02.js
@@ -0,0 +1,130 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const TEST_URL = `data:text/html;charset=utf-8,
+                    <div style='
+                        position:absolute;
+                        left: 0;
+                        top: 0;
+                        width: 40000px;
+                        height: 8000px'>
+                    </div>`;
+
+const PREFIX = "measuring-tool-highlighter-";
+const HIGHLIGHTER_TYPE = "MeasuringToolHighlighter";
+
+const SIDES = ["top", "right", "bottom", "left"];
+
+const X = 32;
+const Y = 20;
+const WIDTH = 160;
+const HEIGHT = 100;
+const HYPOTENUSE = Math.hypot(WIDTH, HEIGHT).toFixed(2);
+
+add_task(function*() {
+  let helper = yield openInspectorForURL(TEST_URL)
+                       .then(getHighlighterHelperFor(HIGHLIGHTER_TYPE));
+
+  let { show, finalize } = helper;
+
+  helper.prefix = PREFIX;
+
+  yield show();
+
+  yield hasNoLabelsWhenStarts(helper);
+  yield hasSizeLabelWhenMoved(helper);
+  yield hasCorrectSizeLabelValue(helper);
+  yield hasSizeLabelAndGuidesWhenStops(helper);
+  yield hasCorrectSizeLabelValue(helper);
+
+  yield finalize();
+});
+
+function* hasNoLabelsWhenStarts({isElementHidden, synthesizeMouse}) {
+  info("Checking highlighter has no labels when we start to select");
+
+  yield synthesizeMouse({
+    selector: ":root",
+    options: {type: "mousedown"},
+    x: X,
+    y: Y
+  });
+
+  let hidden = yield isElementHidden("label-size");
+  ok(hidden, "label's size still hidden");
+
+  hidden = yield isElementHidden("label-position");
+  ok(hidden, "label's position still hidden");
+
+  info("Checking highlighter has no guides when we start to select");
+
+  let guidesHidden = true;
+  for (let side of SIDES) {
+    guidesHidden = guidesHidden && (yield isElementHidden("guide-" + side));
+  }
+
+  ok(guidesHidden, "guides are hidden during dragging");
+}
+
+function* hasSizeLabelWhenMoved({isElementHidden, synthesizeMouse}) {
+  info("Checking highlighter has size label when we select the area");
+
+  yield synthesizeMouse({
+    selector: ":root",
+    options: {type: "mousemove"},
+    x: X + WIDTH,
+    y: Y + HEIGHT
+  });
+
+  let hidden = yield isElementHidden("label-size");
+  is(hidden, false, "label's size is visible during selection");
+
+  hidden = yield isElementHidden("label-position");
+  ok(hidden, "label's position still hidden");
+
+  info("Checking highlighter has no guides when we select the area");
+
+  let guidesHidden = true;
+  for (let side of SIDES) {
+    guidesHidden = guidesHidden && (yield isElementHidden("guide-" + side));
+  }
+
+  ok(guidesHidden, "guides are hidden during selection");
+}
+
+function* hasSizeLabelAndGuidesWhenStops({isElementHidden, synthesizeMouse}) {
+  info("Checking highlighter has size label and guides when we stop");
+
+  yield synthesizeMouse({
+    selector: ":root",
+    options: {type: "mouseup"},
+    x: X + WIDTH,
+    y: Y + HEIGHT
+  });
+
+  let hidden = yield isElementHidden("label-size");
+  is(hidden, false, "label's size is visible when the selection is done");
+
+  hidden = yield isElementHidden("label-position");
+  ok(hidden, "label's position still hidden");
+
+  let guidesVisible = true;
+  for (let side of SIDES) {
+    guidesVisible = guidesVisible && !(yield isElementHidden("guide-" + side));
+  }
+
+  ok(guidesVisible, "guides are visible when the selection is done");
+}
+
+function* hasCorrectSizeLabelValue({getElementTextContent}) {
+  let text = yield getElementTextContent("label-size");
+
+  let [width, height, hypot] = text.match(/\d.*px/g);
+
+  is(parseFloat(width), WIDTH, "width on label's size is correct");
+  is(parseFloat(height), HEIGHT, "height on label's size is correct");
+  is(parseFloat(hypot), HYPOTENUSE, "hypotenuse on label's size is correct");
+}
diff --git a/devtools/client/inspector/test/head.js b/devtools/client/inspector/test/head.js
index b401bd0a51a2..f4dfae0306c9 100644
--- a/devtools/client/inspector/test/head.js
+++ b/devtools/client/inspector/test/head.js
@@ -480,3 +480,57 @@ function dispatchCommandEvent(node) {
                                 false, false, null);
   node.dispatchEvent(commandEvent);
 }
+
+/**
+ * Encapsulate some common operations for highlighter's tests, to have
+ * the tests cleaner, without exposing directly `inspector`, `highlighter`, and
+ * `testActor` if not needed.
+ *
+ * @param  {String}
+ *    The highlighter's type
+ * @return
+ *    A generator function that takes an object with `inspector` and `testActor`
+ *    properties. (see `openInspector`)
+ */
+const getHighlighterHelperFor = (type) => Task.async(
+  function*({inspector, testActor}) {
+    let front = inspector.inspector;
+    let highlighter = yield front.getHighlighterByType(type);
+
+    let prefix = "";
+
+    return {
+      set prefix(value) {
+        prefix = value;
+      },
+
+      show: function*(selector = ":root") {
+        let node = yield getNodeFront(selector, inspector);
+        yield highlighter.show(node);
+      },
+
+      isElementHidden: function*(id) {
+        return (yield testActor.getHighlighterNodeAttribute(
+          prefix + id, "hidden", highlighter)) === "true";
+      },
+
+      getElementTextContent: function*(id) {
+        return yield testActor.getHighlighterNodeTextContent(
+          prefix + id, highlighter);
+      },
+
+      getElementAttribute: function*(id, name) {
+        return yield testActor.getHighlighterNodeAttribute(
+          prefix + id, name, highlighter);
+      },
+
+      synthesizeMouse: function*(options) {
+        yield testActor.synthesizeMouse(options);
+      },
+
+      finalize: function*() {
+        yield highlighter.finalize();
+      }
+    };
+  }
+);
diff --git a/devtools/client/jar.mn b/devtools/client/jar.mn
index 3c85d7c92dce..f4ea632ad978 100644
--- a/devtools/client/jar.mn
+++ b/devtools/client/jar.mn
@@ -205,6 +205,8 @@ devtools.jar:
     skin/themes/images/command-eyedropper@2x.png (themes/images/command-eyedropper@2x.png)
     skin/themes/images/command-rulers.png (themes/images/command-rulers.png)
     skin/themes/images/command-rulers@2x.png (themes/images/command-rulers@2x.png)
+    skin/themes/images/command-measure.png (themes/images/command-measure.png)
+    skin/themes/images/command-measure@2x.png (themes/images/command-measure@2x.png)
     skin/themes/markup-view.css (themes/markup-view.css)
     skin/themes/images/editor-error.png (themes/images/editor-error.png)
     skin/themes/images/editor-breakpoint.png (themes/images/editor-breakpoint.png)
diff --git a/devtools/client/themes/images/command-measure.png b/devtools/client/themes/images/command-measure.png
new file mode 100644
index 000000000000..b7a58f4c5d5c
Binary files /dev/null and b/devtools/client/themes/images/command-measure.png differ
diff --git a/devtools/client/themes/images/command-measure@2x.png b/devtools/client/themes/images/command-measure@2x.png
new file mode 100644
index 000000000000..bb82b59b8ee7
Binary files /dev/null and b/devtools/client/themes/images/command-measure@2x.png differ
diff --git a/devtools/client/themes/toolbars.inc.css b/devtools/client/themes/toolbars.inc.css
index d4253e7d5347..38fc630f82cf 100644
--- a/devtools/client/themes/toolbars.inc.css
+++ b/devtools/client/themes/toolbars.inc.css
@@ -768,6 +768,10 @@
   background-image: url("chrome://devtools/skin/themes/images/command-rulers.png");
 }
 
+#command-button-measure > image {
+  background-image: url("chrome://devtools/skin/themes/images/command-measure.png");
+}
+
 @media (min-resolution: 1.1dppx) {
   #command-button-paintflashing > image {
     background-image: url("chrome://devtools/skin/themes/images/command-paintflashing@2x.png");
@@ -808,6 +812,10 @@
   #command-button-rulers > image {
     background-image: url("chrome://devtools/skin/themes/images/command-rulers@2x.png");
   }
+
+  #command-button-measure > image {
+    background-image: url("chrome://devtools/skin/themes/images/command-measure@2x.png");
+  }
 }
 
 /* Tabs */
diff --git a/devtools/server/actors/highlighters.css b/devtools/server/actors/highlighters.css
index 02718d5f8ad1..1c82c28e3637 100644
--- a/devtools/server/actors/highlighters.css
+++ b/devtools/server/actors/highlighters.css
@@ -273,3 +273,62 @@
   transform: rotate(-90deg);
   text-anchor: end;
 }
+
+/* Measuring Tool highlighter */
+
+:-moz-native-anonymous .measuring-tool-highlighter-root {
+  position: absolute;
+  top: 0;
+  left: 0;
+  pointer-events: auto;
+  cursor: crosshair;
+}
+
+:-moz-native-anonymous .measuring-tool-highlighter-root path {
+  shape-rendering: crispEdges;
+  fill: rgba(135, 206, 235, 0.6);
+  stroke: #08c;
+  pointer-events: none;
+}
+
+:-moz-native-anonymous .dragging path {
+  fill: rgba(135, 206, 235, 0.6);
+  stroke: #08c;
+  opacity: 0.45;
+}
+
+:-moz-native-anonymous .measuring-tool-highlighter-label-size,
+:-moz-native-anonymous .measuring-tool-highlighter-label-position {
+  position: absolute;
+  top: 0;
+  left: 0;
+  display: inline-block;
+  border-radius: 4px;
+  padding: 4px;
+  white-space: pre-line;
+  font: message-box;
+  font-size: 10px;
+  pointer-events: none;
+  -moz-user-select: none;
+  box-sizing: border-box;
+}
+
+:-moz-native-anonymous .measuring-tool-highlighter-label-position {
+  color: #fff;
+  background: hsla(214, 13%, 24%, 0.8);
+}
+
+:-moz-native-anonymous .measuring-tool-highlighter-label-size {
+  color: hsl(216, 33%, 97%);
+  background: hsl(214, 13%, 24%);
+  line-height: 1.5em;
+}
+
+:-moz-native-anonymous .measuring-tool-highlighter-guide-top,
+:-moz-native-anonymous .measuring-tool-highlighter-guide-right,
+:-moz-native-anonymous .measuring-tool-highlighter-guide-bottom,
+:-moz-native-anonymous .measuring-tool-highlighter-guide-left {
+  stroke: #08c;
+  stroke-dasharray: 5 3;
+  shape-rendering: crispEdges;
+}
diff --git a/devtools/server/actors/highlighters.js b/devtools/server/actors/highlighters.js
index f7d3ac34c671..aeb4bd18c590 100644
--- a/devtools/server/actors/highlighters.js
+++ b/devtools/server/actors/highlighters.js
@@ -703,3 +703,7 @@ exports.GeometryEditorHighlighter = GeometryEditorHighlighter;
 const { RulersHighlighter } = require("./highlighters/rulers");
 register(RulersHighlighter);
 exports.RulersHighlighter = RulersHighlighter;
+
+const { MeasuringToolHighlighter } = require("./highlighters/measuring-tool");
+register(MeasuringToolHighlighter);
+exports.MeasuringToolHighlighter = MeasuringToolHighlighter;
diff --git a/devtools/server/actors/highlighters/measuring-tool.js b/devtools/server/actors/highlighters/measuring-tool.js
new file mode 100644
index 000000000000..dae3dc58fd23
--- /dev/null
+++ b/devtools/server/actors/highlighters/measuring-tool.js
@@ -0,0 +1,562 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const events = require("sdk/event/core");
+const { getCurrentZoom,
+  setIgnoreLayoutChanges } = require("devtools/shared/layout/utils");
+const {
+  CanvasFrameAnonymousContentHelper,
+  createSVGNode, createNode } = require("./utils/markup");
+
+// Hard coded value about the size of measuring tool label, in order to
+// position and flip it when is needed.
+const LABEL_SIZE_MARGIN = 8;
+const LABEL_SIZE_WIDTH = 80;
+const LABEL_SIZE_HEIGHT = 52;
+const LABEL_POS_MARGIN = 4;
+const LABEL_POS_WIDTH = 40;
+const LABEL_POS_HEIGHT = 34;
+
+const SIDES = ["top", "right", "bottom", "left"];
+
+/**
+ * The MeasuringToolHighlighter is used to measure distances in a content page.
+ * It allows users to click and drag with their mouse to draw an area whose
+ * dimensions will be displayed in a tooltip next to it.
+ * This allows users to measure distances between elements on a page.
+ */
+function MeasuringToolHighlighter(highlighterEnv) {
+  this.env = highlighterEnv;
+  this.markup = new CanvasFrameAnonymousContentHelper(highlighterEnv,
+    this._buildMarkup.bind(this));
+
+  this.coords = {
+    x: 0,
+    y: 0
+  };
+
+  let { pageListenerTarget } = highlighterEnv;
+
+  pageListenerTarget.addEventListener("mousedown", this);
+  pageListenerTarget.addEventListener("mousemove", this);
+  pageListenerTarget.addEventListener("mouseleave", this);
+  pageListenerTarget.addEventListener("scroll", this);
+  pageListenerTarget.addEventListener("pagehide", this);
+}
+
+MeasuringToolHighlighter.prototype = {
+  typeName: "MeasuringToolHighlighter",
+
+  ID_CLASS_PREFIX: "measuring-tool-highlighter-",
+
+  _buildMarkup() {
+    let prefix = this.ID_CLASS_PREFIX;
+    let { window } = this.env;
+
+    let container = createNode(window, {
+      attributes: {"class": "highlighter-container"}
+    });
+
+    let root = createNode(window, {
+      parent: container,
+      attributes: {
+        "id": "root",
+        "class": "root",
+      },
+      prefix
+    });
+
+    let svg = createSVGNode(window, {
+      nodeType: "svg",
+      parent: root,
+      attributes: {
+        id: "elements",
+        "class": "elements",
+        width: "100%",
+        height: "100%",
+        hidden: "true"
+      },
+      prefix
+    });
+
+    createNode(window, {
+      nodeType: "label",
+      attributes: {
+        id: "label-size",
+        "class": "label-size",
+        "hidden": "true"
+      },
+      parent: root,
+      prefix
+    });
+
+    createNode(window, {
+      nodeType: "label",
+      attributes: {
+        id: "label-position",
+        "class": "label-position",
+        "hidden": "true"
+      },
+      parent: root,
+      prefix
+    });
+
+    // Creating a <g> element in order to group all the paths below, that
+    // together represent the measuring tool; so that would be easier move them
+    // around
+    let g = createSVGNode(window, {
+      nodeType: "g",
+      attributes: {
+        id: "tool",
+      },
+      parent: svg,
+      prefix
+    });
+
+    createSVGNode(window, {
+      nodeType: "path",
+      attributes: {
+        id: "box-path"
+      },
+      parent: g,
+      prefix
+    });
+
+    createSVGNode(window, {
+      nodeType: "path",
+      attributes: {
+        id: "diagonal-path"
+      },
+      parent: g,
+      prefix
+    });
+
+    for (let side of SIDES) {
+      createSVGNode(window, {
+        nodeType: "line",
+        parent: svg,
+        attributes: {
+          "class": `guide-${side}`,
+          id: `guide-${side}`,
+          hidden: "true"
+        },
+        prefix
+      });
+    }
+
+    return container;
+  },
+
+  _update() {
+    let { window } = this.env;
+
+    setIgnoreLayoutChanges(true);
+
+    let zoom = getCurrentZoom(window);
+
+    let { documentElement } = window.document;
+
+    let width = Math.max(documentElement.clientWidth,
+                         documentElement.scrollWidth,
+                         documentElement.offsetWidth);
+
+    let height = Math.max(documentElement.clientHeight,
+                          documentElement.scrollHeight,
+                          documentElement.offsetHeight);
+
+    let { body } = window.document;
+
+    // get the size of the content document despite the compatMode
+    if (body) {
+      width = Math.max(width, body.scrollWidth, body.offsetWidth);
+      height = Math.max(height, body.scrollHeight, body.offsetHeight);
+    }
+
+    let { coords } = this;
+
+    let isZoomChanged = zoom !== coords.zoom;
+
+    if (isZoomChanged) {
+      coords.zoom = zoom;
+      this.updateLabel();
+    }
+
+    let isDocumentSizeChanged = width !== coords.documentWidth ||
+                                height !== coords.documentHeight;
+
+    if (isDocumentSizeChanged) {
+      coords.documentWidth = width;
+      coords.documentHeight = height;
+    }
+
+    // If either the document's size or the zoom is changed since the last
+    // repaint, we update the tool's size as well.
+    if (isZoomChanged || isDocumentSizeChanged) {
+      this.updateViewport();
+    }
+
+    setIgnoreLayoutChanges(false, documentElement);
+
+    this._rafID = window.requestAnimationFrame(() => this._update());
+  },
+
+  _cancelUpdate() {
+    if (this._rafID) {
+      this.env.window.cancelAnimationFrame(this._rafID);
+      this._rafID = 0;
+    }
+  },
+
+  destroy() {
+    this.hide();
+
+    this._cancelUpdate();
+
+    let { pageListenerTarget } = this.env;
+
+    pageListenerTarget.removeEventListener("mousedown", this);
+    pageListenerTarget.removeEventListener("mousemove", this);
+    pageListenerTarget.removeEventListener("mouseup", this);
+    pageListenerTarget.removeEventListener("scroll", this);
+    pageListenerTarget.removeEventListener("pagehide", this);
+
+    this.markup.destroy();
+
+    events.emit(this, "destroy");
+  },
+
+  show() {
+    setIgnoreLayoutChanges(true);
+
+    this.getElement("elements").removeAttribute("hidden");
+
+    this._update();
+
+    setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+  },
+
+  hide() {
+    setIgnoreLayoutChanges(true);
+
+    this.hideLabel("size");
+    this.hideLabel("position");
+
+    this.getElement("elements").setAttribute("hidden", "true");
+
+    this._cancelUpdate();
+
+    setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+  },
+
+  getElement(id) {
+    return this.markup.getElement(this.ID_CLASS_PREFIX + id);
+  },
+
+  setSize(w, h) {
+    this.setCoords(undefined, undefined, w, h);
+  },
+
+  setCoords(x, y, w, h) {
+    let { coords } = this;
+
+    if (typeof x !== "undefined") {
+      coords.x = x;
+    }
+
+    if (typeof y !== "undefined") {
+      coords.y = y;
+    }
+
+    if (typeof w !== "undefined") {
+      coords.w = w;
+    }
+
+    if (typeof h !== "undefined") {
+      coords.h = h;
+    }
+
+    setIgnoreLayoutChanges(true);
+
+    if (this._isDragging) {
+      this.updatePaths();
+    }
+
+    this.updateLabel();
+
+    setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+  },
+
+  updatePaths() {
+    let { x, y, w, h } = this.coords;
+    let dir = `M0 0 L${w} 0 L${w} ${h} L0 ${h}z`;
+
+    // Adding correction to the line path, otherwise some pixels are drawn
+    // outside the main rectangle area.
+    let x1 = w > 0 ? 0.5 : 0;
+    let y1 = w < 0 && h < 0 ? -0.5 : 0;
+    let w1 = w + (h < 0 && w < 0 ? 0.5 : 0);
+    let h1 = h + (h > 0 && w > 0 ? -0.5 : 0);
+
+    let linedir = `M${x1} ${y1} L${w1} ${h1}`;
+
+    this.getElement("box-path").setAttribute("d", dir);
+    this.getElement("diagonal-path").setAttribute("d", linedir);
+    this.getElement("tool").setAttribute("transform", `translate(${x},${y})`);
+  },
+
+  updateLabel(type) {
+    type = type || this._isDragging ? "size" : "position";
+
+    let isSizeLabel = type === "size";
+
+    let label = this.getElement(`label-${type}`);
+
+    let origin = "top left";
+
+    let { innerWidth, innerHeight, scrollX, scrollY } = this.env.window;
+    let { x, y, w, h, zoom } = this.coords;
+    let scale = 1 / zoom;
+
+    w = w || 0;
+    h = h || 0;
+    x = (x || 0) + w;
+    y = (y || 0) + h;
+
+    let labelMargin, labelHeight, labelWidth;
+
+    if (isSizeLabel) {
+      labelMargin = LABEL_SIZE_MARGIN;
+      labelWidth = LABEL_SIZE_WIDTH;
+      labelHeight = LABEL_SIZE_HEIGHT;
+
+      let d = Math.hypot(w, h).toFixed(2);
+
+      label.setTextContent(`W: ${Math.abs(w)} px
+                            H: ${Math.abs(h)} px
+                            ↘: ${d}px`);
+    } else {
+      labelMargin = LABEL_POS_MARGIN;
+      labelWidth = LABEL_POS_WIDTH;
+      labelHeight = LABEL_POS_HEIGHT;
+
+      label.setTextContent(`${x}
+                            ${y}`);
+    }
+
+    // Size used to position properly the label
+    let labelBoxWidth = (labelWidth + labelMargin) * scale;
+    let labelBoxHeight = (labelHeight + labelMargin) * scale;
+
+    let isGoingLeft = w < scrollX;
+    let isSizeGoingLeft = isSizeLabel && isGoingLeft;
+    let isExceedingLeftMargin = x - labelBoxWidth < scrollX;
+    let isExceedingRightMargin = x + labelBoxWidth > innerWidth + scrollX;
+    let isExceedingTopMargin = y - labelBoxHeight < scrollY;
+    let isExceedingBottomMargin = y + labelBoxHeight > innerHeight + scrollY;
+
+    if ((isSizeGoingLeft && !isExceedingLeftMargin) || isExceedingRightMargin) {
+      x -= labelBoxWidth;
+      origin = "top right";
+    } else {
+      x += labelMargin * scale;
+    }
+
+    if (isSizeLabel) {
+      y += isExceedingTopMargin ? labelMargin * scale : -labelBoxHeight;
+    } else {
+      y += isExceedingBottomMargin ? -labelBoxHeight : labelMargin * scale;
+    }
+
+    label.setAttribute("style", `
+      width: ${labelWidth}px;
+      height: ${labelHeight}px;
+      transform-origin: ${origin};
+      transform: translate(${x}px,${y}px) scale(${scale})
+    `);
+
+    if (!isSizeLabel) {
+      let labelSize = this.getElement("label-size");
+      let style = labelSize.getAttribute("style");
+
+      if (style) {
+        labelSize.setAttribute("style",
+          style.replace(/scale[^)]+\)/, `scale(${scale})`));
+      }
+    }
+  },
+
+  updateViewport() {
+    let { scrollX, scrollY, devicePixelRatio } = this.env.window;
+    let { documentWidth, documentHeight, zoom } = this.coords;
+
+    // Because `devicePixelRatio` is affected by zoom (see bug 809788),
+    // in order to get the "real" device pixel ratio, we need divide by `zoom`
+    let pixelRatio = devicePixelRatio / zoom;
+
+    // The "real" device pixel ratio is used to calculate the max stroke
+    // width we can actually assign: on retina, for instance, it would be 0.5,
+    // where on non high dpi monitor would be 1.
+    let minWidth = 1 / pixelRatio;
+    let strokeWidth = Math.min(minWidth, minWidth / zoom);
+
+    this.getElement("root").setAttribute("style",
+      `stroke-width:${strokeWidth};
+       width:${documentWidth}px;
+       height:${documentHeight}px;
+       transform: translate(${-scrollX}px,${-scrollY}px)`);
+  },
+
+  updateGuides() {
+    let { x, y, w, h } = this.coords;
+
+    let guide = this.getElement("guide-top");
+
+    guide.setAttribute("x1", "0");
+    guide.setAttribute("y1", y);
+    guide.setAttribute("x2", "100%");
+    guide.setAttribute("y2", y);
+
+    guide = this.getElement("guide-right");
+
+    guide.setAttribute("x1", x + w);
+    guide.setAttribute("y1", 0);
+    guide.setAttribute("x2", x + w);
+    guide.setAttribute("y2", "100%");
+
+    guide = this.getElement("guide-bottom");
+
+    guide.setAttribute("x1", "0");
+    guide.setAttribute("y1", y + h);
+    guide.setAttribute("x2", "100%");
+    guide.setAttribute("y2", y + h);
+
+    guide = this.getElement("guide-left");
+
+    guide.setAttribute("x1", x);
+    guide.setAttribute("y1", 0);
+    guide.setAttribute("x2", x);
+    guide.setAttribute("y2", "100%");
+  },
+
+  showLabel(type) {
+    setIgnoreLayoutChanges(true);
+
+    this.getElement(`label-${type}`).removeAttribute("hidden");
+
+    setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+  },
+
+  hideLabel(type) {
+    setIgnoreLayoutChanges(true);
+
+    this.getElement(`label-${type}`).setAttribute("hidden", "true");
+
+    setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+  },
+
+  showGuides() {
+    let prefix = this.ID_CLASS_PREFIX + "guide-";
+
+    for (let side of SIDES) {
+      this.markup.removeAttributeForElement(`${prefix + side}`, "hidden");
+    }
+  },
+
+  hideGuides() {
+    let prefix = this.ID_CLASS_PREFIX + "guide-";
+
+    for (let side of SIDES) {
+      this.markup.setAttributeForElement(`${prefix + side}`, "hidden", "true");
+    }
+  },
+
+  handleEvent(event) {
+    let scrollX, scrollY, innerWidth, innerHeight;
+    let x, y;
+
+    let { pageListenerTarget } = this.env;
+
+    switch (event.type) {
+      case "mousedown":
+        if (event.button) {
+          return;
+        }
+
+        this._isDragging = true;
+
+        let { window } = this.env;
+
+        ({ scrollX, scrollY } = window);
+        x = event.clientX + scrollX;
+        y = event.clientY + scrollY;
+
+        pageListenerTarget.addEventListener("mouseup", this);
+
+        setIgnoreLayoutChanges(true);
+
+        this.getElement("tool").setAttribute("class", "dragging");
+
+        this.hideLabel("size");
+        this.hideLabel("position");
+
+        this.hideGuides();
+        this.setCoords(x, y, 0, 0);
+
+        setIgnoreLayoutChanges(false, window.document.documentElement);
+
+        break;
+      case "mouseup":
+        this._isDragging = false;
+
+        pageListenerTarget.removeEventListener("mouseup", this);
+
+        setIgnoreLayoutChanges(true);
+
+        this.getElement("tool").removeAttribute("class", "");
+
+        // Shows the guides only if an actual area is selected
+        if (this.coords.w !== 0 && this.coords.h !== 0) {
+          this.updateGuides();
+          this.showGuides();
+        }
+
+        setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+
+        break;
+      case "mousemove":
+        ({ scrollX, scrollY, innerWidth, innerHeight } = this.env.window);
+        x = event.clientX + scrollX;
+        y = event.clientY + scrollY;
+
+        let { coords } = this;
+
+        x = Math.min(innerWidth + scrollX - 1, Math.max(0 + scrollX, x));
+        y = Math.min(innerHeight + scrollY, Math.max(1 + scrollY, y));
+
+        this.setSize(x - coords.x, y - coords.y);
+
+        let type = this._isDragging ? "size" : "position";
+
+        this.showLabel(type);
+        break;
+      case "mouseleave":
+        if (!this._isDragging) {
+          this.hideLabel("position");
+        }
+        break;
+      case "scroll":
+        setIgnoreLayoutChanges(true);
+        this.updateViewport();
+        setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+
+        break;
+      case "pagehide":
+        this.destroy();
+        break;
+    }
+  }
+};
+exports.MeasuringToolHighlighter = MeasuringToolHighlighter;
diff --git a/devtools/server/actors/highlighters/moz.build b/devtools/server/actors/highlighters/moz.build
index 7b5240e5b812..9dde37795102 100644
--- a/devtools/server/actors/highlighters/moz.build
+++ b/devtools/server/actors/highlighters/moz.build
@@ -13,6 +13,7 @@ DevToolsModules(
     'box-model.js',
     'css-transform.js',
     'geometry-editor.js',
+    'measuring-tool.js',
     'rect.js',
     'rulers.js',
     'selector.js',
diff --git a/devtools/shared/gcli/commands/index.js b/devtools/shared/gcli/commands/index.js
index a7f83e3396ca..fe4c6e67e39e 100644
--- a/devtools/shared/gcli/commands/index.js
+++ b/devtools/shared/gcli/commands/index.js
@@ -65,6 +65,7 @@ exports.devtoolsModules = [
   "devtools/shared/gcli/commands/inject",
   "devtools/shared/gcli/commands/jsb",
   "devtools/shared/gcli/commands/listen",
+  "devtools/shared/gcli/commands/measure",
   "devtools/shared/gcli/commands/media",
   "devtools/shared/gcli/commands/pagemod",
   "devtools/shared/gcli/commands/paintflashing",
diff --git a/devtools/shared/gcli/commands/measure.js b/devtools/shared/gcli/commands/measure.js
new file mode 100644
index 000000000000..7f6233a95c9f
--- /dev/null
+++ b/devtools/shared/gcli/commands/measure.js
@@ -0,0 +1,112 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+ /* globals getOuterId, getBrowserForTab */
+
+"use strict";
+
+const EventEmitter = require("devtools/shared/event-emitter");
+const eventEmitter = new EventEmitter();
+const events = require("sdk/event/core");
+
+loader.lazyRequireGetter(this, "getOuterId", "sdk/window/utils", true);
+loader.lazyRequireGetter(this, "getBrowserForTab", "sdk/tabs/utils", true);
+
+const l10n = require("gcli/l10n");
+require("devtools/server/actors/inspector");
+const { MeasuringToolHighlighter, HighlighterEnvironment } =
+  require("devtools/server/actors/highlighters");
+
+const highlighters = new WeakMap();
+const visibleHighlighters = new Set();
+
+const isCheckedFor = (tab) =>
+  tab ? visibleHighlighters.has(getBrowserForTab(tab).outerWindowID) : false;
+
+exports.items = [
+  // The client measure command is used to maintain the toolbar button state
+  // only and redirects to the server command to actually toggle the measuring
+  // tool (see `measure_server` below).
+  {
+    name: "measure",
+    runAt: "client",
+    description: l10n.lookup("measureDesc"),
+    manual: l10n.lookup("measureManual"),
+    buttonId: "command-button-measure",
+    buttonClass: "command-button command-button-invertable",
+    tooltipText: l10n.lookup("measureTooltip"),
+    state: {
+      isChecked: ({_tab}) => isCheckedFor(_tab),
+      onChange: (target, handler) => eventEmitter.on("changed", handler),
+      offChange: (target, handler) => eventEmitter.off("changed", handler)
+    },
+    exec: function*(args, context) {
+      let { target } = context.environment;
+
+      // Pipe the call to the server command.
+      let response = yield context.updateExec("measure_server");
+      let { visible, id } = response.data;
+
+      if (visible) {
+        visibleHighlighters.add(id);
+      } else {
+        visibleHighlighters.delete(id);
+      }
+
+      eventEmitter.emit("changed", { target });
+
+      // Toggle off the button when the page navigates because the measuring
+      // tool is removed automatically by the MeasuringToolHighlighter on the
+      // server then.
+      let onNavigate = () => {
+        visibleHighlighters.delete(id);
+        eventEmitter.emit("changed", { target });
+      };
+      target.off("will-navigate", onNavigate);
+      target.once("will-navigate", onNavigate);
+    }
+  },
+  // The server measure command is hidden by default, it's just used by the
+  // client command.
+  {
+    name: "measure_server",
+    runAt: "server",
+    hidden: true,
+    returnType: "highlighterVisibility",
+    exec: function(args, context) {
+      let env = context.environment;
+      let { document } = env;
+      let id = getOuterId(env.window);
+
+      // Calling the command again after the measuring tool has been shown once,
+      // hides it.
+      if (highlighters.has(document)) {
+        let { highlighter } = highlighters.get(document);
+        highlighter.destroy();
+        return {visible: false, id};
+      }
+
+      // Otherwise, display the measuring tool.
+      let environment = new HighlighterEnvironment();
+      environment.initFromWindow(env.window);
+      let highlighter = new MeasuringToolHighlighter(environment);
+
+      // Store the instance of the measuring tool highlighter for this document
+      // so we can hide it later.
+      highlighters.set(document, { highlighter, environment });
+
+      // Listen to the highlighter's destroy event which may happen if the
+      // window is refreshed or closed with the measuring tool shown.
+      events.once(highlighter, "destroy", () => {
+        if (highlighters.has(document)) {
+          let { environment } = highlighters.get(document);
+          environment.destroy();
+          highlighters.delete(document);
+        }
+      });
+
+      highlighter.show();
+      return {visible: true, id};
+    }
+  }
+];
diff --git a/devtools/shared/gcli/commands/moz.build b/devtools/shared/gcli/commands/moz.build
index 109a6395b3a6..d902dc52f46a 100644
--- a/devtools/shared/gcli/commands/moz.build
+++ b/devtools/shared/gcli/commands/moz.build
@@ -17,6 +17,7 @@ DevToolsModules(
     'inject.js',
     'jsb.js',
     'listen.js',
+    'measure.js',
     'media.js',
     'pagemod.js',
     'paintflashing.js',
diff --git a/toolkit/locales/en-US/chrome/global/devtools/gclicommands.properties b/toolkit/locales/en-US/chrome/global/devtools/gclicommands.properties
index 69e27c8148c5..1afa7698cac0 100644
--- a/toolkit/locales/en-US/chrome/global/devtools/gclicommands.properties
+++ b/toolkit/locales/en-US/chrome/global/devtools/gclicommands.properties
@@ -1618,3 +1618,17 @@ rulersManual=Toggle the horizontal and vertical rulers for the current page
 # LOCALIZATION NOTE (rulersTooltip) A string displayed as the
 # tooltip of button in devtools toolbox which toggles the rulers.
 rulersTooltip=Toggle rulers for the page
+
+# LOCALIZATION NOTE (measureDesc) A very short description of the
+# 'measure' command. See measureManual for a fuller description of what
+# it does. This string is designed to be shown in a menu alongside the
+# command name, which is why it should be as short as possible.
+measureDesc=Measure a portion of the page
+
+# LOCALIZATION NOTE (measureManual) A fuller description of the 'measure'
+# command, displayed when the user asks for help on what it does.
+measureManual=Activate the measuring tool to measure an arbitrary area of the page
+
+# LOCALIZATION NOTE (measureTooltip) A string displayed as the
+# tooltip of button in devtools toolbox which toggles the measuring tool.
+measureTooltip=Measure a portion of the page