diff --git a/browser/components/migration/src/SafariProfileMigrator.js b/browser/components/migration/src/SafariProfileMigrator.js
index eb1435990c91..6c42f7d6db80 100644
--- a/browser/components/migration/src/SafariProfileMigrator.js
+++ b/browser/components/migration/src/SafariProfileMigrator.js
@@ -342,6 +342,29 @@ Preferences.prototype = {
         this._set("WebKitDisplayImagesKey", "permissions.default.image",
                   function(webkitVal) webkitVal ? 1 : 2);
 
+        // Default charset migration
+        this._set("WebKitDefaultTextEncodingName", "intl.charset.default",
+          function(webkitCharset) {
+            // We don't support x-mac-korean (see bug 713516), but it mostly matches
+            // EUC-KR.
+            if (webkitCharset == "x-mac-korean")
+              return "EUC-KR";
+
+            // getCharsetAlias throws if an invalid value is passed in.
+            try {
+              return Cc["@mozilla.org/charset-converter-manager;1"].
+                     getService(Ci.nsICharsetConverterManager).
+                     getCharsetAlias(webkitCharset);
+            }
+            catch(ex) {
+              Cu.reportError("Could not convert webkit charset '" + webkitCharset +
+                             "' to a supported charset");
+            }
+            // Don't set the preference if we could not get the corresponding
+            // charset.
+            return undefined;
+          });
+
 #ifdef XP_WIN
         // Cookie-accept policy.
         // For the OS X version, see WebFoundationCookieBehavior.
diff --git a/content/html/document/src/nsHTMLDocument.cpp b/content/html/document/src/nsHTMLDocument.cpp
index 23f7876a23e4..c04d02052879 100644
--- a/content/html/document/src/nsHTMLDocument.cpp
+++ b/content/html/document/src/nsHTMLDocument.cpp
@@ -83,7 +83,6 @@
 #include "nsBidiUtils.h"
 
 #include "mozilla/dom/EncodingUtils.h"
-#include "mozilla/dom/FallbackEncoding.h"
 #include "nsIEditingSession.h"
 #include "nsIEditor.h"
 #include "nsNodeInfoManager.h"
@@ -446,13 +445,26 @@ nsHTMLDocument::TryParentCharset(nsIDocShell*  aDocShell,
 }
 
 void
-nsHTMLDocument::TryFallback(int32_t& aCharsetSource, nsACString& aCharset)
+nsHTMLDocument::TryWeakDocTypeDefault(int32_t& aCharsetSource,
+                                      nsACString& aCharset)
 {
-  if (kCharsetFromFallback <= aCharsetSource)
+  if (kCharsetFromWeakDocTypeDefault <= aCharsetSource)
     return;
 
-  aCharsetSource = kCharsetFromFallback;
-  FallbackEncoding::FromLocale(aCharset);
+  const nsAdoptingCString& defCharset =
+    Preferences::GetLocalizedCString("intl.charset.default");
+
+  // Don't let the user break things by setting intl.charset.default to
+  // not a rough ASCII superset
+  nsAutoCString canonical;
+  if (EncodingUtils::FindEncodingForLabel(defCharset, canonical) &&
+      EncodingUtils::IsAsciiCompatible(canonical)) {
+    aCharset = canonical;
+  } else {
+    aCharset.AssignLiteral("windows-1252");
+  }
+  aCharsetSource = kCharsetFromWeakDocTypeDefault;
+  return;
 }
 
 void
@@ -630,7 +642,7 @@ nsHTMLDocument::StartDocumentLoad(const char* aCommand,
   }
 
   if (!IsHTML() || !docShell) { // no docshell for text/html XHR
-    charsetSource = IsHTML() ? kCharsetFromFallback
+    charsetSource = IsHTML() ? kCharsetFromWeakDocTypeDefault
                              : kCharsetFromDocTypeDefault;
     charset.AssignLiteral("UTF-8");
     TryChannelCharset(aChannel, charsetSource, charset, executor);
@@ -671,7 +683,7 @@ nsHTMLDocument::StartDocumentLoad(const char* aCommand,
       TryCacheCharset(cachingChan, charsetSource, charset);
     }
 
-    TryFallback(charsetSource, charset);
+    TryWeakDocTypeDefault(charsetSource, charset);
 
     if (wyciwygChannel) {
       // We know for sure that the parser needs to be using UTF16.
diff --git a/content/html/document/src/nsHTMLDocument.h b/content/html/document/src/nsHTMLDocument.h
index dd0a4d7c0a60..97fab21066cd 100644
--- a/content/html/document/src/nsHTMLDocument.h
+++ b/content/html/document/src/nsHTMLDocument.h
@@ -313,7 +313,8 @@ protected:
                                 nsACString& aCharset);
   void TryParentCharset(nsIDocShell*  aDocShell,
                         int32_t& charsetSource, nsACString& aCharset);
-  static void TryFallback(int32_t& aCharsetSource, nsACString& aCharset);
+  static void TryWeakDocTypeDefault(int32_t& aCharsetSource,
+                                    nsACString& aCharset);
 
   // Override so we can munge the charset on our wyciwyg channel as needed.
   virtual void SetDocumentCharacterSet(const nsACString& aCharSetID) MOZ_OVERRIDE;
diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index b7f782de70a6..180ca9cd555c 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -1896,7 +1896,7 @@ nsDocShell::GatherCharsetMenuTelemetry()
 
   int32_t charsetSource = doc->GetDocumentCharacterSetSource();
   switch (charsetSource) {
-    case kCharsetFromFallback:
+    case kCharsetFromWeakDocTypeDefault:
     case kCharsetFromDocTypeDefault:
     case kCharsetFromCache:
     case kCharsetFromParentFrame:
diff --git a/dom/encoding/FallbackEncoding.cpp b/dom/encoding/FallbackEncoding.cpp
deleted file mode 100644
index 55f7692a1e12..000000000000
--- a/dom/encoding/FallbackEncoding.cpp
+++ /dev/null
@@ -1,137 +0,0 @@
-/* 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/. */
-
-#include "mozilla/dom/FallbackEncoding.h"
-
-#include "mozilla/dom/EncodingUtils.h"
-#include "nsUConvPropertySearch.h"
-#include "nsIChromeRegistry.h"
-#include "mozilla/Preferences.h"
-#include "mozilla/Services.h"
-
-namespace mozilla {
-namespace dom {
-
-static const char* localesFallbacks[][3] = {
-#include "localesfallbacks.properties.h"
-};
-
-FallbackEncoding* FallbackEncoding::sInstance = nullptr;
-
-FallbackEncoding::FallbackEncoding()
-{
-  MOZ_COUNT_CTOR(FallbackEncoding);
-  MOZ_ASSERT(!FallbackEncoding::sInstance,
-             "Singleton already exists.");
-}
-
-FallbackEncoding::~FallbackEncoding()
-{
-  MOZ_COUNT_DTOR(FallbackEncoding);
-}
-
-void
-FallbackEncoding::Get(nsACString& aFallback)
-{
-  if (!mFallback.IsEmpty()) {
-    aFallback = mFallback;
-    return;
-  }
-
-  const nsAdoptingCString& override =
-    Preferences::GetCString("intl.charset.fallback.override");
-  // Don't let the user break things by setting the override to unreasonable
-  // values via about:config
-  if (!EncodingUtils::FindEncodingForLabel(override, mFallback) ||
-      !EncodingUtils::IsAsciiCompatible(mFallback) ||
-      mFallback.EqualsLiteral("UTF-8")) {
-    mFallback.Truncate();
-  }
-
-  if (!mFallback.IsEmpty()) {
-    aFallback = mFallback;
-    return;
-  }
-
-  nsAutoCString locale;
-  nsCOMPtr<nsIXULChromeRegistry> registry =
-    mozilla::services::GetXULChromeRegistryService();
-  if (registry) {
-    registry->GetSelectedLocale(NS_LITERAL_CSTRING("global"), locale);
-  }
-
-  // Let's lower case the string just in case unofficial language packs
-  // don't stick to conventions.
-  ToLowerCase(locale); // ASCII lowercasing with CString input!
-
-  // Special case Traditional Chinese before throwing away stuff after the
-  // language itself. Today we only ship zh-TW, but be defensive about
-  // possible future values.
-  if (locale.EqualsLiteral("zh-tw") ||
-      locale.EqualsLiteral("zh-hk") ||
-      locale.EqualsLiteral("zh-mo") ||
-      locale.EqualsLiteral("zh-hant")) {
-    mFallback.AssignLiteral("Big5");
-    aFallback = mFallback;
-    return;
-  }
-
-  // Throw away regions and other variants to accommodate weird stuff seen
-  // in telemetry--apparently unofficial language packs.
-  int32_t index = locale.FindChar('-');
-  if (index >= 0) {
-    locale.Truncate(index);
-  }
-
-  if (NS_FAILED(nsUConvPropertySearch::SearchPropertyValue(
-      localesFallbacks, ArrayLength(localesFallbacks), locale, mFallback))) {
-    mFallback.AssignLiteral("windows-1252");
-  }
-
-  aFallback = mFallback;
-}
-
-void
-FallbackEncoding::FromLocale(nsACString& aFallback)
-{
-  MOZ_ASSERT(FallbackEncoding::sInstance,
-             "Using uninitialized fallback cache.");
-  FallbackEncoding::sInstance->Get(aFallback);
-}
-
-// PrefChangedFunc
-int
-FallbackEncoding::PrefChanged(const char*, void*)
-{
-  MOZ_ASSERT(FallbackEncoding::sInstance,
-             "Pref callback called with null fallback cache.");
-  FallbackEncoding::sInstance->Invalidate();
-  return 0;
-}
-
-void
-FallbackEncoding::Initialize()
-{
-  MOZ_ASSERT(!FallbackEncoding::sInstance,
-             "Initializing pre-existing fallback cache.");
-  FallbackEncoding::sInstance = new FallbackEncoding;
-  Preferences::RegisterCallback(FallbackEncoding::PrefChanged,
-                                "intl.charset.fallback.override",
-                                nullptr);
-  Preferences::RegisterCallback(FallbackEncoding::PrefChanged,
-                                "general.useragent.locale",
-                                nullptr);
-}
-
-void
-FallbackEncoding::Shutdown()
-{
-  MOZ_ASSERT(FallbackEncoding::sInstance,
-             "Releasing non-existent fallback cache.");
-  delete FallbackEncoding::sInstance;
-  FallbackEncoding::sInstance = nullptr;
-}
-
-} // namespace dom
-} // namespace mozilla
diff --git a/dom/encoding/FallbackEncoding.h b/dom/encoding/FallbackEncoding.h
deleted file mode 100644
index eca99627c4d8..000000000000
--- a/dom/encoding/FallbackEncoding.h
+++ /dev/null
@@ -1,72 +0,0 @@
-/* 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/. */
-
-#ifndef mozilla_dom_FallbackEncoding_h_
-#define mozilla_dom_FallbackEncoding_h_
-
-#include "nsString.h"
-
-namespace mozilla {
-namespace dom {
-
-class FallbackEncoding
-{
-public:
-
-  /**
-   * Gets the locale-dependent fallback encoding for legacy HTML and plain
-   * text content.
-   *
-   * @param aFallback the outparam for the fallback encoding
-   */
-  static void FromLocale(nsACString& aFallback);
-
-  // public API ends here!
-
-  /**
-   * Allocate sInstance used by FromLocale().
-   * To be called from nsLayoutStatics only.
-   */
-  static void Initialize();
-
-  /**
-   * Delete sInstance used by FromLocale().
-   * To be called from nsLayoutStatics only.
-   */
-  static void Shutdown();
-
-private:
-
-  /**
-   * The fallback cache.
-   */
-  static FallbackEncoding* sInstance;
-
-  FallbackEncoding();
-  ~FallbackEncoding();
-
-  /**
-   * Invalidates the cache.
-   */
-  void Invalidate()
-  {
-    mFallback.Truncate();
-  }
-
-  static int PrefChanged(const char*, void*);
-
-  /**
-   * Gets the fallback encoding label.
-   * @param aFallback the fallback encoding
-   */
-  void Get(nsACString& aFallback);
-
-  nsCString mFallback;
-};
-
-} // dom
-} // mozilla
-
-#endif // mozilla_dom_FallbackEncoding_h_
-
diff --git a/dom/encoding/Makefile.in b/dom/encoding/Makefile.in
index ff79a6acbd5f..2fc86207c3ae 100644
--- a/dom/encoding/Makefile.in
+++ b/dom/encoding/Makefile.in
@@ -9,15 +9,11 @@ LOCAL_INCLUDES = \
 include $(topsrcdir)/config/rules.mk
 
 EncodingUtils.$(OBJ_SUFFIX): labelsencodings.properties.h
-FallbackEncoding.$(OBJ_SUFFIX): localesfallbacks.properties.h
 
 PROPS2ARRAYS = $(topsrcdir)/intl/locale/src/props2arrays.py
 labelsencodings.properties.h: $(PROPS2ARRAYS) labelsencodings.properties
 	$(PYTHON) $^ $@
-localesfallbacks.properties.h: $(PROPS2ARRAYS) localesfallbacks.properties
-	$(PYTHON) $^ $@
 
 GARBAGE += \
-	labelsencodings.properties.h \
-	localesfallbacks.properties.h \
+	charsetalias.properties.h \
 	$(NULL)
diff --git a/dom/encoding/localesfallbacks.properties b/dom/encoding/localesfallbacks.properties
deleted file mode 100644
index e014034124e4..000000000000
--- a/dom/encoding/localesfallbacks.properties
+++ /dev/null
@@ -1,72 +0,0 @@
-# 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/.
-
-# This file contains mappings from languages to legacy encodings for languages
-# that are associated with legacy encoding other than windows-1252 (except
-# Traditional Chinese, which is handled as a special case elsewhere).
-#
-# The keys are language codes without regions. The values are Gecko-canonical
-# encoding labels (not necessarily lower case!).
-#
-# Rules:
-#
-# * Avoid editing this file!
-#
-# * If you do edit this file, be sure to file a spec bug against WHATWG HTML
-#   to keep this file in sync with
-#   http://www.whatwg.org/specs/web-apps/current-work/multipage/parsing.html#determining-the-character-encoding
-#
-# * As an exception to the previous rule, gbk is used instead of GB18030 
-#   until/unless work on http://encoding.spec.whatwg.org/ shows that the former
-#   can be treated as an alias of the latter and our decoder implementation 
-#   has been audited to match the spec.
-#
-# * Use only the language code without a hyphen or anything that would come
-#   after the hyphen.
-#
-# * Don't put windows-1252-affiliated languages here.
-#
-# * Don't put Traditional Chinese here.
-
-ar=windows-1256
-# https://www.w3.org/Bugs/Public/show_bug.cgi?id=23089
-ba=windows-1251
-# https://www.w3.org/Bugs/Public/show_bug.cgi?id=23089
-be=windows-1251
-bg=windows-1251
-cs=windows-1250
-# https://www.w3.org/Bugs/Public/show_bug.cgi?id=23090
-el=ISO-8859-7
-et=windows-1257
-fa=windows-1256
-he=windows-1255
-hr=windows-1250
-hu=ISO-8859-2
-ja=Shift_JIS
-# https://www.w3.org/Bugs/Public/show_bug.cgi?id=23089
-kk=windows-1251
-ko=EUC-KR
-ku=windows-1254
-# https://www.w3.org/Bugs/Public/show_bug.cgi?id=23089
-ky=windows-1251
-lt=windows-1257
-lv=windows-1257
-# https://www.w3.org/Bugs/Public/show_bug.cgi?id=23089
-mk=windows-1251
-pl=ISO-8859-2
-ru=windows-1251
-# https://www.w3.org/Bugs/Public/show_bug.cgi?id=23089
-sah=windows-1251
-sk=windows-1250
-sl=ISO-8859-2
-sr=windows-1251
-# https://www.w3.org/Bugs/Public/show_bug.cgi?id=23089
-tg=windows-1251
-th=windows-874
-tr=windows-1254
-# https://www.w3.org/Bugs/Public/show_bug.cgi?id=23089
-tt=windows-1251
-uk=windows-1251
-vi=windows-1258
-zh=gbk
diff --git a/dom/encoding/moz.build b/dom/encoding/moz.build
index df07c3092892..3e8eda067ca9 100644
--- a/dom/encoding/moz.build
+++ b/dom/encoding/moz.build
@@ -10,14 +10,12 @@ MODULE = 'dom'
 
 EXPORTS.mozilla.dom += [
     'EncodingUtils.h',
-    'FallbackEncoding.h',
     'TextDecoder.h',
     'TextEncoder.h',
 ]
 
 SOURCES += [
     'EncodingUtils.cpp',
-    'FallbackEncoding.cpp',
     'TextDecoder.cpp',
     'TextEncoder.cpp',
 ]
diff --git a/extensions/universalchardet/tests/CharsetDetectionTests.js b/extensions/universalchardet/tests/CharsetDetectionTests.js
index 54dd6651a009..71e219a93bdb 100644
--- a/extensions/universalchardet/tests/CharsetDetectionTests.js
+++ b/extensions/universalchardet/tests/CharsetDetectionTests.js
@@ -45,9 +45,17 @@ function InitDetectorTests()
     $("testframe").onload = DoDetectionTest;
 
     if (gExpectedCharset == "default") {
-        // No point trying to be generic here, because we have plenty of other
-        // unit tests that fail if run using a non-windows-1252 locale.
-        gExpectedCharset = "windows-1252";
+        try {
+            gExpectedCharset = prefService
+                .getComplexValue("intl.charset.default",
+                                 Ci.nsIPrefLocalizedString)
+                .data;
+            if (gExpectedCharset == "ISO-8859-1") {
+                gExpectedCharset = "windows-1252";
+            }
+        } catch (e) {
+            gExpectedCharset = "windows-1252";
+        }
     }
 
     // Get the local directory. This needs to be a file: URI because chrome:
diff --git a/layout/build/nsLayoutStatics.cpp b/layout/build/nsLayoutStatics.cpp
index f1227c5699e0..8b3840d71cde 100644
--- a/layout/build/nsLayoutStatics.cpp
+++ b/layout/build/nsLayoutStatics.cpp
@@ -50,7 +50,6 @@
 #include "nsCrossSiteListenerProxy.h"
 #include "nsHTMLDNSPrefetch.h"
 #include "nsHtml5Module.h"
-#include "mozilla/dom/FallbackEncoding.h"
 #include "nsFocusManager.h"
 #include "nsListControlFrame.h"
 #include "mozilla/dom/HTMLInputElement.h"
@@ -259,7 +258,6 @@ nsLayoutStatics::Initialize()
 
   nsContentSink::InitializeStatics();
   nsHtml5Module::InitializeStatics();
-  mozilla::dom::FallbackEncoding::Initialize();
   nsLayoutUtils::Initialize();
   nsIPresShell::InitializeStatics();
   nsRefreshDriver::InitializeStatics();
@@ -386,8 +384,6 @@ nsLayoutStatics::Shutdown()
 
   nsHtml5Module::ReleaseStatics();
 
-  mozilla::dom::FallbackEncoding::Shutdown();
-
   nsRegion::ShutdownStatic();
 
   NS_ShutdownEventTargetChainRecycler();
diff --git a/modules/libpref/src/init/all.js b/modules/libpref/src/init/all.js
index ec0f6e3e64ae..5bad6ac48351 100644
--- a/modules/libpref/src/init/all.js
+++ b/modules/libpref/src/init/all.js
@@ -1520,7 +1520,7 @@ pref("intl.charsetmenu.mailview.cache",     "");
 pref("intl.charsetmenu.composer.cache",     "");
 pref("intl.charsetmenu.browser.cache.size", 5);
 pref("intl.charset.detector",               "chrome://global/locale/intl.properties");
-pref("intl.charset.fallback.override",      "");
+pref("intl.charset.default",                "chrome://global-platform/locale/intl.properties");
 pref("intl.ellipsis",                       "chrome://global-platform/locale/intl.properties");
 pref("intl.locale.matchOS",                 false);
 // fallback charset list for Unicode conversion (converting from Unicode)
diff --git a/netwerk/streamconv/converters/nsDirIndexParser.cpp b/netwerk/streamconv/converters/nsDirIndexParser.cpp
index 66b8cdb10129..ea115ee8723a 100644
--- a/netwerk/streamconv/converters/nsDirIndexParser.cpp
+++ b/netwerk/streamconv/converters/nsDirIndexParser.cpp
@@ -35,7 +35,24 @@ nsDirIndexParser::Init() {
   mLineStart = 0;
   mHasDescription = false;
   mFormat = nullptr;
-  mozilla::dom::FallbackEncoding::FromLocale(mEncoding);
+
+  // get default charset to be used for directory listings (fallback to
+  // ISO-8859-1 if pref is unavailable).
+  NS_NAMED_LITERAL_CSTRING(kFallbackEncoding, "ISO-8859-1");
+  nsXPIDLString defCharset;
+  nsCOMPtr<nsIPrefBranch> prefs(do_GetService(NS_PREFSERVICE_CONTRACTID));
+  if (prefs) {
+    nsCOMPtr<nsIPrefLocalizedString> prefVal;
+    prefs->GetComplexValue("intl.charset.default",
+                           NS_GET_IID(nsIPrefLocalizedString),
+                           getter_AddRefs(prefVal));
+    if (prefVal)
+      prefVal->ToString(getter_Copies(defCharset));
+  }
+  if (!defCharset.IsEmpty())
+    LossyCopyUTF16toASCII(defCharset, mEncoding); // charset labels are always ASCII
+  else
+    mEncoding.Assign(kFallbackEncoding);
  
   nsresult rv;
   // XXX not threadsafe
diff --git a/parser/html/nsHtml5StreamParser.cpp b/parser/html/nsHtml5StreamParser.cpp
index b8708b663158..78018187a856 100644
--- a/parser/html/nsHtml5StreamParser.cpp
+++ b/parser/html/nsHtml5StreamParser.cpp
@@ -302,7 +302,7 @@ nsHtml5StreamParser::SetupDecodingAndWriteSniffingBufferAndCurrentSegment(const
   rv = convManager->GetUnicodeDecoder(mCharset.get(), getter_AddRefs(mUnicodeDecoder));
   if (rv == NS_ERROR_UCONV_NOCONV) {
     mCharset.AssignLiteral("windows-1252"); // lower case is the raw form
-    mCharsetSource = kCharsetFromFallback;
+    mCharsetSource = kCharsetFromWeakDocTypeDefault;
     rv = convManager->GetUnicodeDecoderRaw(mCharset.get(), getter_AddRefs(mUnicodeDecoder));
     mTreeBuilder->SetDocumentCharset(mCharset, mCharsetSource);
   }
@@ -612,10 +612,10 @@ nsHtml5StreamParser::FinalizeSniffing(const uint8_t* aFromSegment, // can be nul
   if (mCharsetSource == kCharsetUninitialized) {
     // Hopefully this case is never needed, but dealing with it anyway
     mCharset.AssignLiteral("windows-1252");
-    mCharsetSource = kCharsetFromFallback;
+    mCharsetSource = kCharsetFromWeakDocTypeDefault;
     mTreeBuilder->SetDocumentCharset(mCharset, mCharsetSource);
   } else if (mMode == LOAD_AS_DATA &&
-             mCharsetSource == kCharsetFromFallback) {
+             mCharsetSource == kCharsetFromWeakDocTypeDefault) {
     NS_ASSERTION(mReparseForbidden, "Reparse should be forbidden for XHR");
     NS_ASSERTION(!mFeedChardet, "Should not feed chardet for XHR");
     NS_ASSERTION(mCharset.EqualsLiteral("UTF-8"),
@@ -731,7 +731,7 @@ nsHtml5StreamParser::SniffStreamBytes(const uint8_t* aFromSegment,
       // nsHTMLDocument is supposed to make sure this does not happen. Let's
       // deal with this anyway, since who knows how kCharsetFromOtherComponent
       // is used.
-      mCharsetSource = kCharsetFromFallback;
+      mCharsetSource = kCharsetFromWeakDocTypeDefault;
     }
   }
 
@@ -981,7 +981,7 @@ nsHtml5StreamParser::OnStartRequest(nsIRequest* aRequest, nsISupports* aContext)
   // if we failed to get a decoder, there will be fallback, so don't propagate
   //  the error.
   if (NS_FAILED(rv)) {
-    mCharsetSource = kCharsetFromFallback;
+    mCharsetSource = kCharsetFromWeakDocTypeDefault;
   }
   return NS_OK;
 }
diff --git a/parser/nsCharsetSource.h b/parser/nsCharsetSource.h
index cd555e25e3ba..825a362ba673 100644
--- a/parser/nsCharsetSource.h
+++ b/parser/nsCharsetSource.h
@@ -7,7 +7,7 @@
 
 // note: the value order defines the priority; higher numbers take priority
 #define kCharsetUninitialized           0
-#define kCharsetFromFallback            1
+#define kCharsetFromWeakDocTypeDefault  1
 #define kCharsetFromDocTypeDefault      2 // This and up confident for XHR
 #define kCharsetFromCache               3
 #define kCharsetFromParentFrame         4
diff --git a/toolkit/components/search/nsSearchService.js b/toolkit/components/search/nsSearchService.js
index 889fc19bb259..6583c8975129 100644
--- a/toolkit/components/search/nsSearchService.js
+++ b/toolkit/components/search/nsSearchService.js
@@ -564,8 +564,7 @@ function queryCharsetFromCode(aCode) {
   if (codes[aCode])
     return codes[aCode];
 
-  // Don't bother being fancy about what to return in the failure case.
-  return "windows-1252";
+  return getLocalizedPref("intl.charset.default", DEFAULT_QUERY_CHARSET);
 }
 function fileCharsetFromCode(aCode) {
   const codes = [
diff --git a/toolkit/locales/en-US/chrome/global-platform/mac/intl.properties b/toolkit/locales/en-US/chrome/global-platform/mac/intl.properties
index 71265a9ef105..93ba2e3a4039 100644
--- a/toolkit/locales/en-US/chrome/global-platform/mac/intl.properties
+++ b/toolkit/locales/en-US/chrome/global-platform/mac/intl.properties
@@ -2,6 +2,8 @@
 # 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/.
 
+# moved from navigator/locale/navigator.properties
+intl.charset.default=ISO-8859-1
 # LOCALIZATION NOTE (intl.ellipsis): Use the unicode ellipsis char, \u2026,
 # or use "..." if \u2026 doesn't suit traditions in your locale.
 intl.ellipsis=…
diff --git a/toolkit/locales/en-US/chrome/global-platform/unix/intl.properties b/toolkit/locales/en-US/chrome/global-platform/unix/intl.properties
index 71265a9ef105..93ba2e3a4039 100644
--- a/toolkit/locales/en-US/chrome/global-platform/unix/intl.properties
+++ b/toolkit/locales/en-US/chrome/global-platform/unix/intl.properties
@@ -2,6 +2,8 @@
 # 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/.
 
+# moved from navigator/locale/navigator.properties
+intl.charset.default=ISO-8859-1
 # LOCALIZATION NOTE (intl.ellipsis): Use the unicode ellipsis char, \u2026,
 # or use "..." if \u2026 doesn't suit traditions in your locale.
 intl.ellipsis=…
diff --git a/toolkit/locales/en-US/chrome/global-platform/win/intl.properties b/toolkit/locales/en-US/chrome/global-platform/win/intl.properties
index 71265a9ef105..93ba2e3a4039 100644
--- a/toolkit/locales/en-US/chrome/global-platform/win/intl.properties
+++ b/toolkit/locales/en-US/chrome/global-platform/win/intl.properties
@@ -2,6 +2,8 @@
 # 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/.
 
+# moved from navigator/locale/navigator.properties
+intl.charset.default=ISO-8859-1
 # LOCALIZATION NOTE (intl.ellipsis): Use the unicode ellipsis char, \u2026,
 # or use "..." if \u2026 doesn't suit traditions in your locale.
 intl.ellipsis=…
diff --git a/toolkit/locales/en-US/chrome/global/intl.properties b/toolkit/locales/en-US/chrome/global/intl.properties
index a144a68aff4c..a9e270529195 100644
--- a/toolkit/locales/en-US/chrome/global/intl.properties
+++ b/toolkit/locales/en-US/chrome/global/intl.properties
@@ -40,7 +40,7 @@ intl.accept_languages=en-US, en
 # http://mxr.mozilla.org/mozilla/source/browser/components/preferences/fonts.xul
 font.language.group=x-western
 
-# LOCALIZATION NOTE (intl.charset.detector, intl.charsetmenu.browser.static, intl.charsetmenu.mailedit):
+# LOCALIZATION NOTE (intl.charset.detector, intl.charset.default, intl.charsetmenu.browser.static, intl.charsetmenu.mailedit):
 # For the list of canonical charset values, refer to:
 # http://mxr.mozilla.org/mozilla-central/source/intl/locale/src/charsetalias.properties
 #
@@ -51,6 +51,7 @@ font.language.group=x-western
 # Note also that the list of charsets in 'intl.charsetmenu.browser.static'
 # must always include "UTF-8".
 intl.charset.detector=
+intl.charset.default=ISO-8859-1
 intl.charsetmenu.browser.static=ISO-8859-1, UTF-8
 intl.charsetmenu.mailedit=ISO-8859-1, ISO-8859-15, ISO-8859-6, armscii-8, ISO-8859-13, ISO-8859-14, ISO-8859-2, GB2312, GB18030, Big5, KOI8-R, windows-1251, KOI8-U, ISO-8859-7, ISO-8859-8-I, windows-1255, ISO-2022-JP, EUC-KR, ISO-8859-10, ISO-8859-3, TIS-620, ISO-8859-9, UTF-8, VISCII