diff --git a/intl/unicharutil/util/nsUnicharUtils.cpp b/intl/unicharutil/util/nsUnicharUtils.cpp
index a3baa7561056..c0e23f1a9f64 100644
--- a/intl/unicharutil/util/nsUnicharUtils.cpp
+++ b/intl/unicharutil/util/nsUnicharUtils.cpp
@@ -162,32 +162,6 @@ void ToFoldedCase(const char16_t* aIn, char16_t* aOut, uint32_t aLen) {
   }
 }
 
-uint32_t ToNaked(uint32_t aChar) {
-  if (IS_ASCII(aChar)) {
-    return aChar;
-  }
-  return mozilla::unicode::GetNaked(aChar);
-}
-
-void ToNaked(nsAString& aString) {
-  char16_t* buf = aString.BeginWriting();
-  ToNaked(buf, buf, aString.Length());
-}
-
-void ToNaked(const char16_t* aIn, char16_t* aOut, uint32_t aLen) {
-  for (uint32_t i = 0; i < aLen; i++) {
-    uint32_t ch = aIn[i];
-    if (i < aLen - 1 && NS_IS_SURROGATE_PAIR(ch, aIn[i + 1])) {
-      ch = mozilla::unicode::GetNaked(SURROGATE_TO_UCS4(ch, aIn[i + 1]));
-      NS_ASSERTION(!IS_IN_BMP(ch), "stripping crossed BMP/SMP boundary!");
-      aOut[i++] = H_SURROGATE(ch);
-      aOut[i] = L_SURROGATE(ch);
-      continue;
-    }
-    aOut[i] = ToNaked(ch);
-  }
-}
-
 int32_t nsCaseInsensitiveStringComparator::operator()(const char16_t* lhs,
                                                       const char16_t* rhs,
                                                       uint32_t lLength,
diff --git a/intl/unicharutil/util/nsUnicharUtils.h b/intl/unicharutil/util/nsUnicharUtils.h
index ea02c5dd5aa9..1f1d1a949ae1 100644
--- a/intl/unicharutil/util/nsUnicharUtils.h
+++ b/intl/unicharutil/util/nsUnicharUtils.h
@@ -56,10 +56,6 @@ uint32_t ToFoldedCase(uint32_t aChar);
 void ToFoldedCase(nsAString& aString);
 void ToFoldedCase(const char16_t* aIn, char16_t* aOut, uint32_t aLen);
 
-uint32_t ToNaked(uint32_t aChar);
-void ToNaked(nsAString& aString);
-void ToNaked(const char16_t* aIn, char16_t* aOut, uint32_t aLen);
-
 class nsCaseInsensitiveStringComparator : public nsStringComparator {
  public:
   nsCaseInsensitiveStringComparator() = default;
diff --git a/intl/unicharutil/util/nsUnicodeProperties.cpp b/intl/unicharutil/util/nsUnicodeProperties.cpp
index fdb1500f5ed0..a03ffc5d5452 100644
--- a/intl/unicharutil/util/nsUnicodeProperties.cpp
+++ b/intl/unicharutil/util/nsUnicodeProperties.cpp
@@ -8,11 +8,8 @@
 #include "nsUnicodePropertyData.cpp"
 
 #include "mozilla/ArrayUtils.h"
-#include "mozilla/HashTable.h"
 #include "nsCharTraits.h"
 
-#include "unicode/normalizer2.h"
-
 #define UNICODE_BMP_LIMIT 0x10000
 #define UNICODE_LIMIT 0x110000
 
@@ -308,50 +305,6 @@ uint32_t CountGraphemeClusters(const char16_t* aText, uint32_t aLength) {
   return result;
 }
 
-uint32_t GetNaked(uint32_t aCh) {
-  using namespace mozilla;
-
-  static const UNormalizer2* normalizer;
-  static HashMap<uint32_t, uint32_t> decompositions;
-
-  HashMap<uint32_t, uint32_t>::Ptr entry = decompositions.lookup(aCh);
-  if (entry.found()) {
-    return entry->value();
-  }
-
-  UErrorCode error = U_ZERO_ERROR;
-  if (!normalizer) {
-    normalizer = unorm2_getNFDInstance(&error);
-    if (U_FAILURE(error)) {
-      return aCh;
-    }
-  }
-
-  UChar ds[16];
-  uint32_t dc;
-  if (unorm2_getDecomposition(normalizer, aCh, ds, sizeof(ds) / sizeof(UChar),
-                              &error) > 0) {
-    if (NS_IS_HIGH_SURROGATE(ds[0])) {
-      dc = SURROGATE_TO_UCS4(ds[0], ds[1]);
-    } else {
-      dc = ds[0];
-    }
-    if (IS_IN_BMP(dc) != IS_IN_BMP(aCh)) {
-      // Mappings that would change the length of a UTF-16 string are not
-      // currently supported.
-      dc = aCh;
-    }
-    if (!decompositions.putNew(aCh, dc)) {
-      // We're out of memory, so delete the cache to free some up.
-      decompositions.clearAndCompact();
-    }
-  } else {
-    dc = aCh;
-  }
-
-  return dc;
-}
-
 }  // end namespace unicode
 
 }  // end namespace mozilla
diff --git a/intl/unicharutil/util/nsUnicodeProperties.h b/intl/unicharutil/util/nsUnicodeProperties.h
index b34a527e360a..8922b1d0b436 100644
--- a/intl/unicharutil/util/nsUnicodeProperties.h
+++ b/intl/unicharutil/util/nsUnicodeProperties.h
@@ -229,9 +229,6 @@ class ClusterIterator {
 // Count the number of grapheme clusters in the given string
 uint32_t CountGraphemeClusters(const char16_t* aText, uint32_t aLength);
 
-// Remove diacritics from a character
-uint32_t GetNaked(uint32_t aCh);
-
 // A simple reverse iterator for a string of char16_t codepoints that
 // advances by Unicode grapheme clusters
 class ClusterReverseIterator {
diff --git a/mobile/android/app/mobile.js b/mobile/android/app/mobile.js
index f75c660fa272..be20405902e5 100644
--- a/mobile/android/app/mobile.js
+++ b/mobile/android/app/mobile.js
@@ -238,7 +238,6 @@ pref("accessibility.typeaheadfind.flashBar", 1);
 pref("accessibility.typeaheadfind.linksonly", false);
 pref("accessibility.typeaheadfind.casesensitive", 0);
 pref("accessibility.browsewithcaret_shortcut.enabled", false);
-pref("findbar.matchdiacritics", 0);
 
 // Whether the character encoding menu is under the main Firefox button. This
 // preference is a string so that localizers can alter it.
diff --git a/mobile/android/modules/geckoview/GeckoViewContent.jsm b/mobile/android/modules/geckoview/GeckoViewContent.jsm
index 684f165ea013..b52a161861e7 100644
--- a/mobile/android/modules/geckoview/GeckoViewContent.jsm
+++ b/mobile/android/modules/geckoview/GeckoViewContent.jsm
@@ -332,7 +332,6 @@ class GeckoViewContent extends GeckoViewModule {
 
     finder.caseSensitive = !!aData.matchCase;
     finder.entireWord = !!aData.wholeWord;
-    finder.matchDiacritics = !!aData.matchDiacritics;
     finder.addResultListener(this._finderListener);
 
     const drawOutline =
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 95ec1ea437f9..6603051b82f8 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -768,11 +768,6 @@ pref("accessibility.typeaheadfind.matchesCountLimit", 1000);
 pref("findbar.highlightAll", false);
 pref("findbar.entireword", false);
 pref("findbar.iteratorTimeout", 100);
-// matchdiacritics: controls the find bar's diacritic matching
-//     0 - "never"  (ignore diacritics)
-//     1 - "always" (match diacritics)
-// other - "auto"   (match diacritics if input has diacritics, ignore otherwise)
-pref("findbar.matchdiacritics", 0);
 
 // use Mac OS X Appearance panel text smoothing setting when rendering text, disabled by default
 pref("gfx.use_text_smoothing_setting", false);
diff --git a/toolkit/actors/FinderChild.jsm b/toolkit/actors/FinderChild.jsm
index 7fb6f39b0f7e..b2a084394098 100644
--- a/toolkit/actors/FinderChild.jsm
+++ b/toolkit/actors/FinderChild.jsm
@@ -28,10 +28,6 @@ class FinderChild extends JSWindowActorChild {
         this.finder.caseSensitive = data.caseSensitive;
         break;
 
-      case "Finder:MatchDiacritics":
-        this.finder.matchDiacritics = data.matchDiacritics;
-        break;
-
       case "Finder:EntireWord":
         this.finder.entireWord = data.entireWord;
         break;
diff --git a/toolkit/components/extensions/FindContent.jsm b/toolkit/components/extensions/FindContent.jsm
index 930a3aea84c4..7ab732a138a4 100644
--- a/toolkit/components/extensions/FindContent.jsm
+++ b/toolkit/components/extensions/FindContent.jsm
@@ -51,7 +51,6 @@ class FindContent {
    * @param {string} queryphrase - the text to search for.
    * @param {boolean} caseSensitive - whether to use case sensitive matches.
    * @param {boolean} includeRangeData - whether to collect and return range data.
-   * @param {boolean} matchDiacritics - whether diacritics must match.
    * @param {boolean} searchString - whether to collect and return rect data.
    *
    * @returns {object} that includes:
@@ -67,7 +66,6 @@ class FindContent {
         entireWord,
         includeRangeData,
         includeRectData,
-        matchDiacritics,
       } = params;
 
       this.iterator.reset();
@@ -79,7 +77,6 @@ class FindContent {
         entireWord: !!entireWord,
         finder: this.finder,
         listener: this.finder,
-        matchDiacritics: !!matchDiacritics,
         useSubFrames: false,
       });
 
diff --git a/toolkit/components/find/nsFind.cpp b/toolkit/components/find/nsFind.cpp
index 4b6a73fd4e58..5e4e2aceee56 100644
--- a/toolkit/components/find/nsFind.cpp
+++ b/toolkit/components/find/nsFind.cpp
@@ -61,10 +61,7 @@ NS_IMPL_CYCLE_COLLECTING_RELEASE(nsFind)
 NS_IMPL_CYCLE_COLLECTION(nsFind)
 
 nsFind::nsFind()
-    : mFindBackward(false),
-      mCaseSensitive(false),
-      mMatchDiacritics(false),
-      mWordBreaker(nullptr) {}
+    : mFindBackward(false), mCaseSensitive(false), mWordBreaker(nullptr) {}
 
 nsFind::~nsFind() = default;
 
@@ -400,22 +397,6 @@ nsFind::SetEntireWord(bool aEntireWord) {
   return NS_OK;
 }
 
-NS_IMETHODIMP
-nsFind::GetMatchDiacritics(bool* aMatchDiacritics) {
-  if (!aMatchDiacritics) {
-    return NS_ERROR_NULL_POINTER;
-  }
-
-  *aMatchDiacritics = mMatchDiacritics;
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-nsFind::SetMatchDiacritics(bool aMatchDiacritics) {
-  mMatchDiacritics = aMatchDiacritics;
-  return NS_OK;
-}
-
 // Here begins the find code. A ten-thousand-foot view of how it works: Find
 // needs to be able to compare across inline (but not block) nodes, e.g. find
 // for "abc" should match a<b>b</b>c. So after we've searched a node, we're not
@@ -526,9 +507,6 @@ nsFind::Find(const nsAString& aPatText, nsRange* aSearchRange,
   if (!mCaseSensitive) {
     ToFoldedCase(patAutoStr);
   }
-  if (!mMatchDiacritics) {
-    ToNaked(patAutoStr);
-  }
 
   // Ignore soft hyphens in the pattern
   static const char kShy[] = {char(CH_SHY), 0};
@@ -707,13 +685,8 @@ nsFind::Find(const nsAString& aPatText, nsRange* aSearchRange,
     }
     if (!inWhitespace && IsSpace(patc)) {
       inWhitespace = true;
-    } else if (!inWhitespace) {
-      if (!mCaseSensitive) {
-        c = ToFoldedCase(c);
-      }
-      if (!mMatchDiacritics) {
-        c = ToNaked(c);
-      }
+    } else if (!inWhitespace && !mCaseSensitive) {
+      c = ToFoldedCase(c);
     }
 
     if (c == CH_SHY) {
diff --git a/toolkit/components/find/nsFind.h b/toolkit/components/find/nsFind.h
index 37668f702709..76cc4537d717 100644
--- a/toolkit/components/find/nsFind.h
+++ b/toolkit/components/find/nsFind.h
@@ -42,7 +42,6 @@ class nsFind : public nsIFind {
   // Parameters set from the interface:
   bool mFindBackward;
   bool mCaseSensitive;
-  bool mMatchDiacritics;
 
   // Use "find entire words" mode by setting to a word breaker or null, to
   // disable "entire words" mode.
diff --git a/toolkit/components/find/nsFindService.cpp b/toolkit/components/find/nsFindService.cpp
index 7499132c2c2c..1d1731787f94 100644
--- a/toolkit/components/find/nsFindService.cpp
+++ b/toolkit/components/find/nsFindService.cpp
@@ -79,13 +79,3 @@ NS_IMETHODIMP nsFindService::SetMatchCase(bool aMatchCase) {
   mMatchCase = aMatchCase;
   return NS_OK;
 }
-
-NS_IMETHODIMP nsFindService::GetMatchDiacritics(bool* aMatchDiacritics) {
-  NS_ENSURE_ARG_POINTER(aMatchDiacritics);
-  *aMatchDiacritics = mMatchDiacritics;
-  return NS_OK;
-}
-NS_IMETHODIMP nsFindService::SetMatchDiacritics(bool aMatchDiacritics) {
-  mMatchDiacritics = aMatchDiacritics;
-  return NS_OK;
-}
diff --git a/toolkit/components/find/nsFindService.h b/toolkit/components/find/nsFindService.h
index 5204076f5d91..595b797728a7 100644
--- a/toolkit/components/find/nsFindService.h
+++ b/toolkit/components/find/nsFindService.h
@@ -40,5 +40,4 @@ class nsFindService : public nsIFindService {
   bool mWrapFind;
   bool mEntireWord;
   bool mMatchCase;
-  bool mMatchDiacritics;
 };
diff --git a/toolkit/components/find/nsIFind.idl b/toolkit/components/find/nsIFind.idl
index 941ed56cacc3..6cae5dff63c7 100644
--- a/toolkit/components/find/nsIFind.idl
+++ b/toolkit/components/find/nsIFind.idl
@@ -15,7 +15,6 @@ interface nsIFind : nsISupports
   attribute boolean findBackwards;
   attribute boolean caseSensitive;
   attribute boolean entireWord;
-  attribute boolean matchDiacritics;
 
   /**
    * Find some text in the current context. The implementation is
diff --git a/toolkit/components/find/nsIFindService.idl b/toolkit/components/find/nsIFindService.idl
index f5a5e18ce653..0c1b0e215e62 100644
--- a/toolkit/components/find/nsIFindService.idl
+++ b/toolkit/components/find/nsIFindService.idl
@@ -22,6 +22,5 @@ interface nsIFindService : nsISupports
     attribute boolean wrapFind;
     attribute boolean entireWord;
     attribute boolean matchCase;
-    attribute boolean matchDiacritics;
 
 };
diff --git a/toolkit/components/find/nsIWebBrowserFind.idl b/toolkit/components/find/nsIWebBrowserFind.idl
index 1a78ea7269a0..634d39973acc 100644
--- a/toolkit/components/find/nsIWebBrowserFind.idl
+++ b/toolkit/components/find/nsIWebBrowserFind.idl
@@ -79,13 +79,6 @@ interface nsIWebBrowserFind : nsISupports
      */
     attribute boolean matchCase;
 
-    /**
-     * matchDiacritics
-     *
-     * Whether to match diacritics when searching. Default is false.
-     */
-    attribute boolean matchDiacritics;
-
     /**
      * searchFrames
      *
diff --git a/toolkit/components/find/nsWebBrowserFind.cpp b/toolkit/components/find/nsWebBrowserFind.cpp
index d61612271969..d1c1f0800959 100644
--- a/toolkit/components/find/nsWebBrowserFind.cpp
+++ b/toolkit/components/find/nsWebBrowserFind.cpp
@@ -54,7 +54,6 @@ nsWebBrowserFind::nsWebBrowserFind()
       mWrapFind(false),
       mEntireWord(false),
       mMatchCase(false),
-      mMatchDiacritics(false),
       mSearchSubFrames(true),
       mSearchParentFrames(true) {}
 
@@ -291,19 +290,6 @@ nsWebBrowserFind::SetMatchCase(bool aMatchCase) {
   return NS_OK;
 }
 
-NS_IMETHODIMP
-nsWebBrowserFind::GetMatchDiacritics(bool* aMatchDiacritics) {
-  NS_ENSURE_ARG_POINTER(aMatchDiacritics);
-  *aMatchDiacritics = mMatchDiacritics;
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-nsWebBrowserFind::SetMatchDiacritics(bool aMatchDiacritics) {
-  mMatchDiacritics = aMatchDiacritics;
-  return NS_OK;
-}
-
 void nsWebBrowserFind::SetSelectionAndScroll(nsPIDOMWindowOuter* aWindow,
                                              nsRange* aRange) {
   RefPtr<Document> doc = aWindow->GetDoc();
@@ -640,7 +626,6 @@ nsresult nsWebBrowserFind::SearchInFrame(nsPIDOMWindowOuter* aWindow,
   NS_ENSURE_SUCCESS(rv, rv);
 
   (void)find->SetCaseSensitive(mMatchCase);
-  (void)find->SetMatchDiacritics(mMatchDiacritics);
   (void)find->SetFindBackwards(mFindBackwards);
 
   (void)find->SetEntireWord(mEntireWord);
diff --git a/toolkit/components/find/nsWebBrowserFind.h b/toolkit/components/find/nsWebBrowserFind.h
index e3d537a1a091..b5cb0f096d3b 100644
--- a/toolkit/components/find/nsWebBrowserFind.h
+++ b/toolkit/components/find/nsWebBrowserFind.h
@@ -81,7 +81,6 @@ class nsWebBrowserFind : public nsIWebBrowserFind,
   bool mWrapFind;
   bool mEntireWord;
   bool mMatchCase;
-  bool mMatchDiacritics;
 
   bool mSearchSubFrames;
   bool mSearchParentFrames;
diff --git a/toolkit/components/typeaheadfind/nsITypeAheadFind.idl b/toolkit/components/typeaheadfind/nsITypeAheadFind.idl
index 2f94136e72bf..9bfb39874921 100644
--- a/toolkit/components/typeaheadfind/nsITypeAheadFind.idl
+++ b/toolkit/components/typeaheadfind/nsITypeAheadFind.idl
@@ -70,7 +70,6 @@ interface nsITypeAheadFind : nsISupports
   readonly attribute AString searchString;
                                         // Most recent search string
   attribute boolean caseSensitive;      // Searches are case sensitive
-  attribute boolean matchDiacritics;    // Searches preserve diacritics
   attribute boolean entireWord;         // Search for whole words only
   readonly attribute Element foundLink;
                                         // Most recent elem found, if a link
diff --git a/toolkit/components/typeaheadfind/nsTypeAheadFind.cpp b/toolkit/components/typeaheadfind/nsTypeAheadFind.cpp
index 434797b8765b..eb5cad390f80 100644
--- a/toolkit/components/typeaheadfind/nsTypeAheadFind.cpp
+++ b/toolkit/components/typeaheadfind/nsTypeAheadFind.cpp
@@ -86,8 +86,7 @@ nsTypeAheadFind::nsTypeAheadFind()
       mLastFindLength(0),
       mIsSoundInitialized(false),
       mCaseSensitive(false),
-      mEntireWord(false),
-      mMatchDiacritics(false) {}
+      mEntireWord(false) {}
 
 nsTypeAheadFind::~nsTypeAheadFind() {
   nsCOMPtr<nsIPrefBranch> prefInternal(
@@ -212,24 +211,6 @@ nsTypeAheadFind::GetEntireWord(bool* isEntireWord) {
   return NS_OK;
 }
 
-NS_IMETHODIMP
-nsTypeAheadFind::SetMatchDiacritics(bool matchDiacritics) {
-  mMatchDiacritics = matchDiacritics;
-
-  if (mFind) {
-    mFind->SetMatchDiacritics(mMatchDiacritics);
-  }
-
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-nsTypeAheadFind::GetMatchDiacritics(bool* matchDiacritics) {
-  *matchDiacritics = mMatchDiacritics;
-
-  return NS_OK;
-}
-
 NS_IMETHODIMP
 nsTypeAheadFind::SetDocShell(nsIDocShell* aDocShell) {
   mDocShell = do_GetWeakReference(aDocShell);
diff --git a/toolkit/components/typeaheadfind/nsTypeAheadFind.h b/toolkit/components/typeaheadfind/nsTypeAheadFind.h
index 388a6f8c2be3..1d265b28e0f3 100644
--- a/toolkit/components/typeaheadfind/nsTypeAheadFind.h
+++ b/toolkit/components/typeaheadfind/nsTypeAheadFind.h
@@ -120,7 +120,6 @@ class nsTypeAheadFind : public nsITypeAheadFind,
 
   bool mCaseSensitive;
   bool mEntireWord;
-  bool mMatchDiacritics;
 
   bool EnsureFind() {
     if (mFind) {
@@ -134,7 +133,6 @@ class nsTypeAheadFind : public nsITypeAheadFind,
 
     mFind->SetCaseSensitive(mCaseSensitive);
     mFind->SetEntireWord(mEntireWord);
-    mFind->SetMatchDiacritics(mMatchDiacritics);
 
     return true;
   }
diff --git a/toolkit/components/windowcreator/test/test_nsFind.html b/toolkit/components/windowcreator/test/test_nsFind.html
index b8a02de77f7b..9689d21a219c 100644
--- a/toolkit/components/windowcreator/test/test_nsFind.html
+++ b/toolkit/components/windowcreator/test/test_nsFind.html
@@ -1,7 +1,6 @@
 <!DOCTYPE HTML>
 <html>
 <!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=202251
 https://bugzilla.mozilla.org/show_bug.cgi?id=450048
 https://bugzilla.mozilla.org/show_bug.cgi?id=969980
 https://bugzilla.mozilla.org/show_bug.cgi?id=1589786
@@ -14,6 +13,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=1589786
 
 <script type="application/javascript">
 
+/** Test for Bug 450048 **/
 SimpleTest.waitForExplicitFinish();
 
 async function runTests() {
@@ -47,13 +47,12 @@ async function runTests() {
   rf.findBackwards = false;
 
   rf.caseSensitive = false;
-  rf.matchDiacritics = false;
 
   searchValue = "TexT";
   retRange = rf.Find(searchValue, searchRange, startPt, endPt);
   ok(retRange, "\"" + searchValue + "\" not found (not caseSensitive)");
 
-  searchValue = "λογος";
+  searchValue = "λόγος";
   retRange = rf.Find(searchValue, searchRange, startPt, endPt);
   ok(retRange, "\"" + searchValue + "\" not found (not caseSensitive)");
 
@@ -65,15 +64,9 @@ async function runTests() {
   retRange = rf.Find(searchValue, searchRange, startPt, endPt);
   ok(retRange, "\"" + searchValue + "\" not found (not caseSensitive)");
 
-  rf.matchDiacritics = true;
-
-  searchValue = "λογος";
-  retRange = rf.Find(searchValue, searchRange, startPt, endPt);
-  ok(!retRange, "\"" + searchValue + "\" found (not caseSensitive)");
-
   rf.caseSensitive = true;
 
-  searchValue = "TexT";
+  // searchValue = "TexT";
   retRange = rf.Find(searchValue, searchRange, startPt, endPt);
   ok(!retRange, "\"" + searchValue + "\" found (caseSensitive)");
 
diff --git a/toolkit/content/tests/chrome/findbar_events_window.xhtml b/toolkit/content/tests/chrome/findbar_events_window.xhtml
index 3cfbe2673139..c81e0763e569 100644
--- a/toolkit/content/tests/chrome/findbar_events_window.xhtml
+++ b/toolkit/content/tests/chrome/findbar_events_window.xhtml
@@ -60,7 +60,6 @@
       await testFind();
       await testFindAgain();
       await testCaseSensitivity();
-      await testDiacriticMatching();
       await testHighlight();
     }
 
@@ -144,24 +143,6 @@
       await ContentTask.spawn(gBrowser, null, () => content.getSelection().removeAllRanges());
     }
 
-    async function testDiacriticMatching() {
-      info("Testing normal diacritic matching.");
-      let promise = once(gFindBar, "finddiacriticmatchingchange", false);
-
-      let matchDiacriticsCheckbox = gFindBar.getElement("find-match-diacritics");
-      matchDiacriticsCheckbox.click();
-
-      let e = await promise;
-      ok(e.detail.matchDiacritics, "find should match diacritics");
-
-      // Toggle it back to the original setting.
-      matchDiacriticsCheckbox.click();
-
-      // Changing diacritic matching does the search so clear the selected text
-      // before the next test.
-      await ContentTask.spawn(gBrowser, null, () => content.getSelection().removeAllRanges());
-    }
-
     async function testHighlight() {
       info("Testing find with highlight all.");
       // Update the find state so the highlight button is clickable.
diff --git a/toolkit/content/tests/chrome/findbar_window.xhtml b/toolkit/content/tests/chrome/findbar_window.xhtml
index f2908ab2166b..1f93e1a82e07 100644
--- a/toolkit/content/tests/chrome/findbar_window.xhtml
+++ b/toolkit/content/tests/chrome/findbar_window.xhtml
@@ -28,7 +28,7 @@
 
     const SAMPLE_URL = "http://www.mozilla.org/";
     const SAMPLE_TEXT = "Some text in a text field.";
-    const SEARCH_TEXT = "Text Test (δοκιμή)";
+    const SEARCH_TEXT = "Text Test";
     const NOT_FOUND_TEXT = "This text is not on the page."
     const ITERATOR_TIMEOUT = gPrefsvc.getIntPref("findbar.iteratorTimeout");
 
@@ -88,7 +88,7 @@
       await new Promise(resolve => setTimeout(resolve, 1000));
 
       let promise = BrowserTestUtils.browserLoaded(gBrowser);
-      BrowserTestUtils.loadURI(gBrowser, "data:text/html;charset=utf-8,<h2 id='h2'>" + SEARCH_TEXT +
+      BrowserTestUtils.loadURI(gBrowser, "data:text/html,<h2 id='h2'>" + SEARCH_TEXT +
         "</h2><h2><a href='" + SAMPLE_URL + "'>Link Test</a></h2><input id='text' type='text' value='" +
         SAMPLE_TEXT + "'></input><input id='button' type='button'></input><img id='img' width='50' height='50'/>",
         { triggeringPrincipal: window.document.nodePrincipal });
@@ -735,24 +735,6 @@
       ok(gFindBar.hidden, "Successful Find Again leaves the find bar closed.");
     }
 
-    async function testToggleDiacriticMatching() {
-      await openFindbar();
-      let promise = promiseFindResult();
-      await enterStringIntoFindField("δοκιμη", false);
-      let result = await promise;
-      is(result.result, Ci.nsITypeAheadFind.FIND_FOUND, "Text should be found");
-
-      await new Promise(resolve => setTimeout(resolve, ITERATOR_TIMEOUT + 20));
-      promise = promiseFindResult();
-      let check = gFindBar.getElement("find-match-diacritics");
-      check.click();
-      result = await promise;
-      is(result.result, Ci.nsITypeAheadFind.FIND_NOTFOUND, "Text should NOT be found");
-
-      check.click();
-      gFindBar.close(true);
-    }
-
     async function testToggleEntireWord() {
       await openFindbar();
       let promise = promiseFindResult();
diff --git a/toolkit/content/widgets/findbar.js b/toolkit/content/widgets/findbar.js
index 8f16b347e0d8..35d5d27f8426 100644
--- a/toolkit/content/widgets/findbar.js
+++ b/toolkit/content/widgets/findbar.js
@@ -30,7 +30,6 @@
   ]);
   const PREFS_TO_OBSERVE_INT = new Map([
     ["typeAheadCaseSensitive", "accessibility.typeaheadfind.casesensitive"],
-    ["matchDiacritics", "findbar.matchdiacritics"],
   ]);
   const PREFS_TO_OBSERVE_ALL = new Map([
     ...PREFS_TO_OBSERVE_BOOL,
@@ -73,12 +72,9 @@
           data-l10n-id="findbar-highlight-all2" oncommand="toggleHighlight(this.checked);" type="checkbox" />
         <toolbarbutton anonid="find-case-sensitive" class="findbar-case-sensitive findbar-button tabbable"
           data-l10n-id="findbar-case-sensitive" oncommand="_setCaseSensitivity(this.checked ? 1 : 0);" type="checkbox" />
-        <toolbarbutton anonid="find-match-diacritics" class="findbar-match-diacritics findbar-button tabbable"
-          data-l10n-id="findbar-match-diacritics" oncommand="_setDiacriticMatching(this.checked ? 1 : 0);" type="checkbox" />
         <toolbarbutton anonid="find-entire-word" class="findbar-entire-word findbar-button tabbable"
           data-l10n-id="findbar-entire-word" oncommand="toggleEntireWord(this.checked);" type="checkbox" />
         <label anonid="match-case-status" class="findbar-find-fast" />
-        <label anonid="match-diacritics-status" class="findbar-find-fast" />
         <label anonid="entire-word-status" class="findbar-find-fast" />
         <label anonid="found-matches" class="findbar-find-fast found-matches" hidden="true" />
         <image anonid="find-status-icon" class="findbar-find-fast find-status-icon" />
@@ -394,9 +390,6 @@
         case "findbar.highlightAll":
           this.toggleHighlight(prefsvc.getBoolPref(prefName), true);
           break;
-        case "findbar.matchdiacritics":
-          this._setDiacriticMatching(prefsvc.getIntPref(prefName));
-          break;
         case "findbar.modalHighlight":
           this._useModalHighlight = prefsvc.getBoolPref(prefName);
           if (this.browser.finder) {
@@ -605,55 +598,6 @@
       this._dispatchFindEvent("casesensitivitychange");
     }
 
-    /**
-     * Updates the diacritic-matching mode of the findbar and its UI.
-     *
-     * @param {String} [str] The string for which diacritic matching might be
-     *                       turned on. This is only used when diacritic
-     *                       matching is in auto mode, see
-     *                       `_shouldMatchDiacritics`. The default value for
-     *                       this parameter is the find-field value.
-     * @see _shouldMatchDiacritics.
-     */
-    _updateDiacriticMatching(str) {
-      let val = str || this._findField.value;
-
-      let matchDiacritics = this._shouldMatchDiacritics(val);
-      let checkbox = this.getElement("find-match-diacritics");
-      let statusLabel = this.getElement("match-diacritics-status");
-      checkbox.checked = matchDiacritics;
-
-      statusLabel.value = matchDiacritics ? this._matchDiacriticsStr : "";
-
-      // Show the checkbox on the full Find bar in non-auto mode.
-      // Show the label in all other cases.
-      let hideCheckbox =
-        this.findMode != this.FIND_NORMAL ||
-        (this._matchDiacritics != 0 && this._matchDiacritics != 1);
-      checkbox.hidden = hideCheckbox;
-      statusLabel.hidden = !hideCheckbox;
-
-      this.browser.finder.matchDiacritics = matchDiacritics;
-    }
-
-    /**
-     * Sets the findbar diacritic-matching mode
-     * @param {Number} diacriticMatching 0 - ignore diacritics,
-     *                                   1 - match diacritics,
-     *                                   2 - auto = match diacritics if the
-     *                                       matching string contains
-     *                                       diacritics.
-     * @see _shouldMatchDiacritics
-     */
-    _setDiacriticMatching(diacriticMatching) {
-      this._matchDiacritics = diacriticMatching;
-      this._updateDiacriticMatching();
-      this._findFailedString = null;
-      this._find();
-
-      this._dispatchFindEvent("diacriticmatchingchange");
-    }
-
     /**
      * Updates the entire-word mode of the findbar and its UI.
      */
@@ -715,7 +659,6 @@
         this._fastFindStr = bundle.GetStringFromName("FastFind");
         this._fastFindLinksStr = bundle.GetStringFromName("FastFindLinks");
         this._caseSensitiveStr = bundle.GetStringFromName("CaseSensitive");
-        this._matchDiacriticsStr = bundle.GetStringFromName("MatchDiacritics");
         this._entireWordStr = bundle.GetStringFromName("EntireWord");
       }
 
@@ -840,17 +783,6 @@
       return str != str.toLowerCase();
     }
 
-    _shouldMatchDiacritics(str) {
-      if (this._matchDiacritics == 0) {
-        return false;
-      }
-      if (this._matchDiacritics == 1) {
-        return true;
-      }
-
-      return str != str.normalize("NFD");
-    }
-
     onMouseUp() {
       if (!this.hidden && this.findMode != this.FIND_NORMAL) {
         this.close();
@@ -952,7 +884,6 @@
       ).hidden = showMinimalUI;
       foundMatches.hidden = showMinimalUI || !foundMatches.value;
       this._updateCaseSensitivity();
-      this._updateDiacriticMatching();
       this._setEntireWord();
       this._setHighlightAll();
 
@@ -1002,7 +933,6 @@
 
         this._enableFindButtons(val);
         this._updateCaseSensitivity(val);
-        this._updateDiacriticMatching(val);
         this._setEntireWord();
 
         this.browser.finder.fastFind(
@@ -1096,7 +1026,6 @@
       event.initCustomEvent("find" + type, true, true, {
         query: this._findField.value,
         caseSensitive: !!this._typeAheadCaseSensitive,
-        matchDiacritics: !!this._matchDiacritics,
         entireWord: this._entireWord,
         highlightAll: this._highlightAll,
         findPrevious,
diff --git a/toolkit/locales/en-US/chrome/global/findbar.properties b/toolkit/locales/en-US/chrome/global/findbar.properties
index 735941afd862..abe037ba7328 100644
--- a/toolkit/locales/en-US/chrome/global/findbar.properties
+++ b/toolkit/locales/en-US/chrome/global/findbar.properties
@@ -10,7 +10,6 @@ NormalFind=Find in page
 FastFind=Quick find
 FastFindLinks=Quick find (links only)
 CaseSensitive=(Case sensitive)
-MatchDiacritics=(Matching diacritics)
 EntireWord=(Whole words only)
 # LOCALIZATION NOTE (FoundMatches): Semicolon-separated list of plural forms.
 # See: http://developer.mozilla.org/en/docs/Localization_and_Plurals
diff --git a/toolkit/locales/en-US/toolkit/main-window/findbar.ftl b/toolkit/locales/en-US/toolkit/main-window/findbar.ftl
index 75daa54d48f9..88d19168abd4 100644
--- a/toolkit/locales/en-US/toolkit/main-window/findbar.ftl
+++ b/toolkit/locales/en-US/toolkit/main-window/findbar.ftl
@@ -25,11 +25,6 @@ findbar-case-sensitive =
     .accesskey = C
     .tooltiptext = Search with case sensitivity
 
-findbar-match-diacritics =
-    .label = Match Diacritics
-    .accesskey = D
-    .tooltiptext = Distinguish between accented letters and their base letters (for example, when searching for "resume", "résumé" will not be matched)
-
 findbar-entire-word =
     .label = Whole Words
     .accesskey = W
diff --git a/toolkit/modules/Finder.jsm b/toolkit/modules/Finder.jsm
index 4c805383e0d2..ec2240c2e433 100644
--- a/toolkit/modules/Finder.jsm
+++ b/toolkit/modules/Finder.jsm
@@ -170,14 +170,6 @@ Finder.prototype = {
     this.iterator.reset();
   },
 
-  set matchDiacritics(aMatchDiacritics) {
-    if (this._fastFind.matchDiacritics === aMatchDiacritics) {
-      return;
-    }
-    this._fastFind.matchDiacritics = aMatchDiacritics;
-    this.iterator.reset();
-  },
-
   set entireWord(aEntireWord) {
     if (this._fastFind.entireWord === aEntireWord) {
       return;
@@ -349,7 +341,6 @@ Finder.prototype = {
         caseSensitive: this._fastFind.caseSensitive,
         entireWord: this._fastFind.entireWord,
         linksOnly: aArgs.linksOnly,
-        matchDiacritics: this._fastFind.matchDiacritics,
         word: aArgs.searchString,
         useSubFrames: aArgs.useSubFrames,
       })
@@ -598,7 +589,6 @@ Finder.prototype = {
       caseSensitive: this._fastFind.caseSensitive,
       entireWord: this._fastFind.entireWord,
       linksOnly: aLinksOnly,
-      matchDiacritics: this._fastFind.matchDiacritics,
       word: aWord,
       useSubFrames: aUseSubFrames,
     };
diff --git a/toolkit/modules/FinderHighlighter.jsm b/toolkit/modules/FinderHighlighter.jsm
index 3dec6de936c5..61bdbc133d5e 100644
--- a/toolkit/modules/FinderHighlighter.jsm
+++ b/toolkit/modules/FinderHighlighter.jsm
@@ -284,7 +284,6 @@ FinderHighlighter.prototype = {
         word,
         finder: this.finder,
         listener: this,
-        matchDiacritics: this.finder._fastFind.matchDiacritics,
         useCache: true,
         useSubFrames,
         window,
diff --git a/toolkit/modules/FinderIterator.jsm b/toolkit/modules/FinderIterator.jsm
index f77ac95703d2..7eb1bcb38c5d 100644
--- a/toolkit/modules/FinderIterator.jsm
+++ b/toolkit/modules/FinderIterator.jsm
@@ -88,8 +88,6 @@ FinderIterator.prototype = {
    *                                           - onIteratorReset();
    *                                           - onIteratorRestart({Object} iterParams);
    *                                           - onIteratorStart({Object} iterParams);
-   * @param {Boolean} options.matchDiacritics Whether to search in
-   *                                          diacritic-matching mode
    * @param {Boolean} [options.useCache]        Whether to allow results already
    *                                            present in the cache or demand fresh.
    *                                            Optional, defaults to `false`.
@@ -106,7 +104,6 @@ FinderIterator.prototype = {
     limit,
     linksOnly,
     listener,
-    matchDiacritics,
     useCache,
     word,
     useSubFrames,
@@ -135,9 +132,6 @@ FinderIterator.prototype = {
     if (typeof entireWord != "boolean") {
       throw new Error("Missing required option 'entireWord'");
     }
-    if (typeof matchDiacritics != "boolean") {
-      throw new Error("Missing required option 'matchDiacritics'");
-    }
     if (!finder) {
       throw new Error("Missing required option 'finder'");
     }
@@ -164,7 +158,6 @@ FinderIterator.prototype = {
       caseSensitive,
       entireWord,
       linksOnly,
-      matchDiacritics,
       useCache,
       window,
       word,
@@ -311,8 +304,6 @@ FinderIterator.prototype = {
    * @param {Boolean}  options.entireWord    Whether to search in entire-word mode
    * @param  {Boolean} options.linksOnly     Whether to search for the word to be
    *                                         present in links only
-   * @param {Boolean}  options.matchDiacritics Whether to search in
-   *                                           diacritic-matching mode
    * @param  {String}  options.word          The word being searched for
    * @param  (Boolean) options.useSubFrames  Whether to search subframes
    * @return {Boolean}
@@ -321,7 +312,6 @@ FinderIterator.prototype = {
     caseSensitive,
     entireWord,
     linksOnly,
-    matchDiacritics,
     word,
     useSubFrames,
   }) {
@@ -330,7 +320,6 @@ FinderIterator.prototype = {
       this._currentParams.caseSensitive === caseSensitive &&
       this._currentParams.entireWord === entireWord &&
       this._currentParams.linksOnly === linksOnly &&
-      this._currentParams.matchDiacritics === matchDiacritics &&
       this._currentParams.word == word &&
       this._currentParams.useSubFrames == useSubFrames
     );
@@ -385,8 +374,6 @@ FinderIterator.prototype = {
    * @param  {Boolean} options.entireWord    Whether to search in entire-word mode
    * @param  {Boolean} options.linksOnly     Whether to search for the word to be
    *                                         present in links only
-   * @param  {Boolean} options.matchDiacritics Whether to search in
-   *                                           diacritic-matching mode
    * @param  {Boolean} options.useCache      Whether the consumer wants to use the
    *                                         cached previous result at all
    * @param  {String}  options.word          The word being searched for
@@ -396,7 +383,6 @@ FinderIterator.prototype = {
     caseSensitive,
     entireWord,
     linksOnly,
-    matchDiacritics,
     useCache,
     word,
   }) {
@@ -406,7 +392,6 @@ FinderIterator.prototype = {
         caseSensitive,
         entireWord,
         linksOnly,
-        matchDiacritics,
         word,
       }) &&
       this._previousRanges.length
@@ -430,7 +415,6 @@ FinderIterator.prototype = {
       paramSet1.caseSensitive === paramSet2.caseSensitive &&
       paramSet1.entireWord === paramSet2.entireWord &&
       paramSet1.linksOnly === paramSet2.linksOnly &&
-      paramSet1.matchDiacritics === paramSet2.matchDiacritics &&
       paramSet1.window === paramSet2.window &&
       paramSet1.useSubFrames === paramSet2.useSubFrames &&
       NLP.levenshtein(paramSet1.word, paramSet2.word) <= allowDistance
@@ -640,16 +624,11 @@ FinderIterator.prototype = {
    *                                             sensitive mode
    * @param {Boolean}      options.entireWord    Whether to search in entire-word
    *                                             mode
-   * @param {Boolean}      options.matchDiacritics Whether to search in
-   *                                               diacritic-matching mode
    * @param {String}       options.word          The word to search for
    * @param {nsIDOMWindow} window                The window to search in
    * @yield {Range}
    */
-  *_iterateDocument(
-    { caseSensitive, entireWord, matchDiacritics, word },
-    window
-  ) {
+  *_iterateDocument({ caseSensitive, entireWord, word }, window) {
     let doc = window.document;
     let body = doc.body || doc.documentElement;
 
@@ -673,7 +652,6 @@ FinderIterator.prototype = {
       .QueryInterface(Ci.nsIFind);
     nsIFind.caseSensitive = caseSensitive;
     nsIFind.entireWord = entireWord;
-    nsIFind.matchDiacritics = matchDiacritics;
 
     while ((retRange = nsIFind.Find(word, searchRange, startPt, endPt))) {
       yield retRange;
diff --git a/toolkit/modules/FinderParent.jsm b/toolkit/modules/FinderParent.jsm
index 4626bc51aa4e..d9c897ff536b 100644
--- a/toolkit/modules/FinderParent.jsm
+++ b/toolkit/modules/FinderParent.jsm
@@ -217,12 +217,6 @@ FinderParent.prototype = {
     });
   },
 
-  set matchDiacritics(aMatchDiacritics) {
-    this.sendMessageToAllContexts("Finder:MatchDiacritics", {
-      matchDiacritics: aMatchDiacritics,
-    });
-  },
-
   async setSearchStringToSelection() {
     return this.setToSelection("Finder:SetSearchStringToSelection", false);
   },
diff --git a/toolkit/modules/tests/xpcshell/test_FinderIterator.js b/toolkit/modules/tests/xpcshell/test_FinderIterator.js
index 7cc06f04c154..e51592c08e7f 100644
--- a/toolkit/modules/tests/xpcshell/test_FinderIterator.js
+++ b/toolkit/modules/tests/xpcshell/test_FinderIterator.js
@@ -58,7 +58,6 @@ add_task(async function test_start() {
         Assert.equal(range.toString(), findText, "Text content should match");
       },
     },
-    matchDiacritics: false,
     word: findText,
   });
 
@@ -89,7 +88,6 @@ add_task(async function test_subframes() {
         Assert.equal(range.toString(), findText, "Text content should match");
       },
     },
-    matchDiacritics: false,
     word: findText,
     useSubFrames: true,
   });
@@ -121,7 +119,6 @@ add_task(async function test_valid_arguments() {
         ++count;
       },
     },
-    matchDiacritics: false,
     word: findText,
   });
 
@@ -140,7 +137,6 @@ add_task(async function test_valid_arguments() {
             ++count;
           },
         },
-        matchDiacritics: false,
         word: findText,
       }),
     /Missing required option 'caseSensitive'/,
@@ -152,7 +148,6 @@ add_task(async function test_valid_arguments() {
     () =>
       finderIterator.start({
         caseSensitive: false,
-        entireWord: false,
         listener: {
           onIteratorRangeFound(range) {
             ++count;
@@ -160,23 +155,6 @@ add_task(async function test_valid_arguments() {
         },
         word: findText,
       }),
-    /Missing required option 'matchDiacritics'/,
-    "Should throw when missing an argument"
-  );
-  finderIterator.reset();
-
-  Assert.throws(
-    () =>
-      finderIterator.start({
-        caseSensitive: false,
-        listener: {
-          onIteratorRangeFound(range) {
-            ++count;
-          },
-        },
-        matchDiacritics: false,
-        word: findText,
-      }),
     /Missing required option 'entireWord'/,
     "Should throw when missing an argument"
   );
@@ -192,7 +170,6 @@ add_task(async function test_valid_arguments() {
             ++count;
           },
         },
-        matchDiacritics: false,
         word: findText,
       }),
     /Missing required option 'finder'/,
@@ -206,7 +183,6 @@ add_task(async function test_valid_arguments() {
         caseSensitive: true,
         entireWord: false,
         finder: gMockFinder,
-        matchDiacritics: false,
         word: findText,
       }),
     /Missing valid, required option 'listener'/,
@@ -225,7 +201,6 @@ add_task(async function test_valid_arguments() {
             ++count;
           },
         },
-        matchDiacritics: false,
       }),
     /Missing required option 'word'/,
     "Should throw when missing an argument"
@@ -250,7 +225,6 @@ add_task(async function test_stop() {
         ++count;
       },
     },
-    matchDiacritics: false,
     word: findText,
   });
 
@@ -278,7 +252,6 @@ add_task(async function test_reset() {
         ++count;
       },
     },
-    matchDiacritics: false,
     word: findText,
   });
 
@@ -321,11 +294,10 @@ add_task(async function test_parallel_starts() {
         ++count;
       },
     },
-    matchDiacritics: false,
     word: findText,
   });
 
-  await new Promise(resolve => gMockWindow.setTimeout(resolve, 100));
+  await new Promise(resolve => gMockWindow.setTimeout(resolve, 120));
   Assert.ok(finderIterator.running, "We ought to be running here");
 
   let count2 = 0;
@@ -338,7 +310,6 @@ add_task(async function test_parallel_starts() {
         ++count2;
       },
     },
-    matchDiacritics: false,
     word: findText,
   });
 
@@ -389,7 +360,6 @@ add_task(async function test_allowDistance() {
         ++count;
       },
     },
-    matchDiacritics: false,
     word: findText,
   });
 
@@ -403,7 +373,6 @@ add_task(async function test_allowDistance() {
         ++count2;
       },
     },
-    matchDiacritics: false,
     word: "gu",
   });
 
@@ -418,7 +387,6 @@ add_task(async function test_allowDistance() {
         ++count3;
       },
     },
-    matchDiacritics: false,
     word: "gu",
   });