diff --git a/accessible/tests/browser/python_runner_wsh.py b/accessible/tests/browser/python_runner_wsh.py
index 488051240f71..2686967cfb7e 100644
--- a/accessible/tests/browser/python_runner_wsh.py
+++ b/accessible/tests/browser/python_runner_wsh.py
@@ -9,6 +9,7 @@ It is intended to be called from JS browser tests.
 """
 
 import json
+import math
 import os
 import sys
 import traceback
@@ -83,6 +84,9 @@ def web_socket_transfer_data(request):
             exec(code, namespace)
             # Run the function we just defined.
             ret = namespace["run"]()
+            if isinstance(ret, float) and math.isnan(ret):
+                # NaN can't be serialized by JSON.
+                ret = None
             send("return", ret)
         except Exception:
             send("exception", traceback.format_exc())
diff --git a/accessible/tests/browser/windows/uia/browser_simplePatterns.js b/accessible/tests/browser/windows/uia/browser_simplePatterns.js
index f464db0e1394..b2326ae3a825 100644
--- a/accessible/tests/browser/windows/uia/browser_simplePatterns.js
+++ b/accessible/tests/browser/windows/uia/browser_simplePatterns.js
@@ -317,6 +317,7 @@ addUiaTask(
     await setUpWaitForUiaPropEvent("ValueValue", "text");
     await runPython(`pattern.SetValue("after")`);
     await waitForUiaEvent();
+    ok(true, "Got ValueValue prop change event on text");
     is(
       await runPython(`pattern.CurrentValue`),
       "after",
@@ -434,6 +435,7 @@ addUiaTask(
     await setUpWaitForUiaPropEvent("ValueValue", "ariaTextbox");
     await runPython(`pattern.SetValue("after")`);
     await waitForUiaEvent();
+    ok(true, "Got ValueValue prop change event on ariaTextbox");
     is(
       await runPython(`pattern.CurrentValue`),
       "after",
@@ -443,3 +445,95 @@ addUiaTask(
     await testPatternAbsent("button", "Value");
   }
 );
+
+async function testRangeValueProps(id, ro, val, min, max, small, large) {
+  await assignPyVarToUiaWithId(id);
+  await definePyVar("pattern", `getUiaPattern(${id}, "RangeValue")`);
+  ok(await runPython(`bool(pattern)`), `${id} has RangeValue pattern`);
+  is(
+    !!(await runPython(`pattern.CurrentIsReadOnly`)),
+    ro,
+    `${id} has IsReadOnly ${ro}`
+  );
+  is(await runPython(`pattern.CurrentValue`), val, `${id} has correct Value`);
+  is(
+    await runPython(`pattern.CurrentMinimum`),
+    min,
+    `${id} has correct Minimum`
+  );
+  is(
+    await runPython(`pattern.CurrentMaximum`),
+    max,
+    `${id} has correct Maximum`
+  );
+  // IA2 doesn't support small/large change, so the IA2 -> UIA proxy can't
+  // either.
+  if (gIsUiaEnabled) {
+    is(
+      await runPython(`pattern.CurrentSmallChange`),
+      small,
+      `${id} has correct SmallChange`
+    );
+    is(
+      await runPython(`pattern.CurrentLargeChange`),
+      large,
+      `${id} has correct LargeChange`
+    );
+  }
+}
+
+/**
+ * Test the RangeValue pattern.
+ */
+addUiaTask(
+  `
+<input id="range" type="range">
+<input id="rangeBig" type="range" max="1000">
+<progress id="progress" value="0.5"></progress>
+<input id="numberRo" type="number" min="0" max="10" value="5" readonly>
+<div id="ariaSlider" role="slider">slider</div>
+<button id="button">button</button>
+  `,
+  async function testRangeValue(browser) {
+    await definePyVar("doc", `getDocUia()`);
+    await testRangeValueProps("range", false, 50, 0, 100, 1, 10);
+    info("SetValue on range");
+    await setUpWaitForUiaPropEvent("RangeValueValue", "range");
+    await runPython(`pattern.SetValue(20)`);
+    await waitForUiaEvent();
+    ok(true, "Got RangeValueValue prop change event on range");
+    is(await runPython(`pattern.CurrentValue`), 20, "range has correct Value");
+
+    await testRangeValueProps("rangeBig", false, 500, 0, 1000, 1, 100);
+
+    // Gecko a11y doesn't expose progress bars as read only, but it probably
+    // should.
+    await testRangeValueProps("progress", false, 0.5, 0, 1, 0, 0.1);
+    info("Calling SetValue on progress");
+    await testPythonRaises(
+      `pattern.SetValue(0.6)`,
+      "SetValue on progress failed"
+    );
+
+    await testRangeValueProps("numberRo", true, 5, 0, 10, 1, 1);
+    info("Calling SetValue on numberRo");
+    await testPythonRaises(
+      `pattern.SetValue(6)`,
+      "SetValue on numberRo failed"
+    );
+
+    await testRangeValueProps("ariaSlider", false, 50, 0, 100, null, null);
+    info("Setting aria-valuenow on ariaSlider");
+    await setUpWaitForUiaPropEvent("RangeValueValue", "ariaSlider");
+    await invokeSetAttribute(browser, "ariaSlider", "aria-valuenow", "60");
+    await waitForUiaEvent();
+    ok(true, "Got RangeValueValue prop change event on ariaSlider");
+    is(
+      await runPython(`pattern.CurrentValue`),
+      60,
+      "ariaSlider has correct Value"
+    );
+
+    await testPatternAbsent("button", "RangeValue");
+  }
+);
diff --git a/accessible/windows/uia/uiaRawElmProvider.cpp b/accessible/windows/uia/uiaRawElmProvider.cpp
index 47b81b13890d..46936cfd8aa0 100644
--- a/accessible/windows/uia/uiaRawElmProvider.cpp
+++ b/accessible/windows/uia/uiaRawElmProvider.cpp
@@ -91,6 +91,12 @@ void uiaRawElmProvider::RaiseUiaEventForGeckoEvent(Accessible* aAcc,
       uia->get_Value(&newVal.bstrVal);
       gotNewVal = true;
       break;
+    case nsIAccessibleEvent::EVENT_VALUE_CHANGE:
+      property = UIA_RangeValueValuePropertyId;
+      newVal.vt = VT_R8;
+      uia->get_Value(&newVal.dblVal);
+      gotNewVal = true;
+      break;
   }
   if (property && ::UiaClientsAreListening()) {
     // We can't get the old value. Thankfully, clients don't seem to need it.
@@ -162,6 +168,8 @@ uiaRawElmProvider::QueryInterface(REFIID aIid, void** aInterface) {
     *aInterface = static_cast<IExpandCollapseProvider*>(this);
   } else if (aIid == IID_IInvokeProvider) {
     *aInterface = static_cast<IInvokeProvider*>(this);
+  } else if (aIid == IID_IRangeValueProvider) {
+    *aInterface = static_cast<IRangeValueProvider*>(this);
   } else if (aIid == IID_IScrollItemProvider) {
     *aInterface = static_cast<IScrollItemProvider*>(this);
   } else if (aIid == IID_IToggleProvider) {
@@ -279,6 +287,12 @@ uiaRawElmProvider::GetPatternProvider(
         invoke.forget(aPatternProvider);
       }
       return S_OK;
+    case UIA_RangeValuePatternId:
+      if (acc->HasNumericValue()) {
+        RefPtr<IValueProvider> value = this;
+        value.forget(aPatternProvider);
+      }
+      return S_OK;
     case UIA_ScrollItemPatternId: {
       RefPtr<IScrollItemProvider> scroll = this;
       scroll.forget(aPatternProvider);
@@ -786,6 +800,99 @@ uiaRawElmProvider::get_IsReadOnly(__RPC__out BOOL* aRetVal) {
   return S_OK;
 }
 
+// IRangeValueProvider methods
+
+STDMETHODIMP
+uiaRawElmProvider::SetValue(double aVal) {
+  Accessible* acc = Acc();
+  if (!acc) {
+    return CO_E_OBJNOTCONNECTED;
+  }
+  if (!acc->SetCurValue(aVal)) {
+    return UIA_E_INVALIDOPERATION;
+  }
+  return S_OK;
+}
+
+STDMETHODIMP
+uiaRawElmProvider::get_Value(__RPC__out double* aRetVal) {
+  if (!aRetVal) {
+    return E_INVALIDARG;
+  }
+  Accessible* acc = Acc();
+  if (!acc) {
+    return CO_E_OBJNOTCONNECTED;
+  }
+  *aRetVal = acc->CurValue();
+  return S_OK;
+}
+
+STDMETHODIMP
+uiaRawElmProvider::get_Maximum(__RPC__out double* aRetVal) {
+  if (!aRetVal) {
+    return E_INVALIDARG;
+  }
+  Accessible* acc = Acc();
+  if (!acc) {
+    return CO_E_OBJNOTCONNECTED;
+  }
+  *aRetVal = acc->MaxValue();
+  return S_OK;
+}
+
+STDMETHODIMP
+uiaRawElmProvider::get_Minimum(
+    /* [retval][out] */ __RPC__out double* aRetVal) {
+  if (!aRetVal) {
+    return E_INVALIDARG;
+  }
+  Accessible* acc = Acc();
+  if (!acc) {
+    return CO_E_OBJNOTCONNECTED;
+  }
+  *aRetVal = acc->MinValue();
+  return S_OK;
+}
+
+STDMETHODIMP
+uiaRawElmProvider::get_LargeChange(
+    /* [retval][out] */ __RPC__out double* aRetVal) {
+  if (!aRetVal) {
+    return E_INVALIDARG;
+  }
+  Accessible* acc = Acc();
+  if (!acc) {
+    return CO_E_OBJNOTCONNECTED;
+  }
+  // We want the change that would occur if the user pressed page up or page
+  // down. For HTML input elements, this is 10% of the total range unless step
+  // is larger. See:
+  // https://searchfox.org/mozilla-central/rev/c7df16ffad1f12a19c81c16bce0b65e4a15304d0/dom/html/HTMLInputElement.cpp#3878
+  double step = acc->Step();
+  double min = acc->MinValue();
+  double max = acc->MaxValue();
+  if (std::isnan(step) || std::isnan(min) || std::isnan(max)) {
+    *aRetVal = UnspecifiedNaN<double>();
+  } else {
+    *aRetVal = std::max(step, (max - min) / 10);
+  }
+  return S_OK;
+}
+
+STDMETHODIMP
+uiaRawElmProvider::get_SmallChange(
+    /* [retval][out] */ __RPC__out double* aRetVal) {
+  if (!aRetVal) {
+    return E_INVALIDARG;
+  }
+  Accessible* acc = Acc();
+  if (!acc) {
+    return CO_E_OBJNOTCONNECTED;
+  }
+  *aRetVal = acc->Step();
+  return S_OK;
+}
+
 // Private methods
 
 bool uiaRawElmProvider::IsControl() {
diff --git a/accessible/windows/uia/uiaRawElmProvider.h b/accessible/windows/uia/uiaRawElmProvider.h
index 4a133a28566e..ad8f0557be78 100644
--- a/accessible/windows/uia/uiaRawElmProvider.h
+++ b/accessible/windows/uia/uiaRawElmProvider.h
@@ -26,7 +26,8 @@ class uiaRawElmProvider : public IAccessibleEx,
                           public IToggleProvider,
                           public IExpandCollapseProvider,
                           public IScrollItemProvider,
-                          public IValueProvider {
+                          public IValueProvider,
+                          public IRangeValueProvider {
  public:
   static constexpr enum ProviderOptions kProviderOptions =
       static_cast<enum ProviderOptions>(ProviderOptions_ServerSideProvider |
@@ -123,6 +124,27 @@ class uiaRawElmProvider : public IAccessibleEx,
   virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_IsReadOnly(
       /* [retval][out] */ __RPC__out BOOL* pRetVal);
 
+  // IRangeValueProvider
+  virtual HRESULT STDMETHODCALLTYPE SetValue(
+      /* [in] */ double aVal);
+
+  virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_Value(
+      /* [retval][out] */ __RPC__out double* aRetVal);
+
+  // get_IsReadOnly is shared with IValueProvider.
+
+  virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_Maximum(
+      /* [retval][out] */ __RPC__out double* aRetVal);
+
+  virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_Minimum(
+      /* [retval][out] */ __RPC__out double* aRetVal);
+
+  virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_LargeChange(
+      /* [retval][out] */ __RPC__out double* aRetVal);
+
+  virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_SmallChange(
+      /* [retval][out] */ __RPC__out double* aRetVal);
+
  private:
   Accessible* Acc() const;
   bool IsControl();