diff --git a/intl/components/src/UnicodeProperties.h b/intl/components/src/UnicodeProperties.h
index 6737d33ad124..3fde1c09fd1b 100644
--- a/intl/components/src/UnicodeProperties.h
+++ b/intl/components/src/UnicodeProperties.h
@@ -171,6 +171,23 @@ class UnicodeProperties final {
     return u_hasBinaryProperty(aCh, prop);
   }
 
+  /**
+   * Check if the width of aCh is full width, half width or wide.
+   */
+  static inline bool IsEastAsianWidthFHW(uint32_t aCh) {
+    switch (GetIntPropertyValue(aCh, IntProperty::EastAsianWidth)) {
+      case U_EA_FULLWIDTH:
+      case U_EA_HALFWIDTH:
+      case U_EA_WIDE:
+        return true;
+      case U_EA_AMBIGUOUS:
+      case U_EA_NARROW:
+      case U_EA_NEUTRAL:
+        return false;
+    }
+    return false;
+  }
+
   /**
    * Check if the width of aCh is full width, half width or wide
    * excluding emoji.
@@ -224,6 +241,24 @@ class UnicodeProperties final {
     return false;
   }
 
+  /**
+   * Check if the CharType of aCh is a punctuation type.
+   */
+  static inline bool IsPunctuation(uint32_t aCh) {
+    switch (CharType(aCh)) {
+      case GeneralCategory::Dash_Punctuation:
+      case GeneralCategory::Open_Punctuation:
+      case GeneralCategory::Close_Punctuation:
+      case GeneralCategory::Connector_Punctuation:
+      case GeneralCategory::Other_Punctuation:
+      case GeneralCategory::Initial_Punctuation:
+      case GeneralCategory::Final_Punctuation:
+        return true;
+      default:
+        return false;
+    }
+  }
+
   /**
    * Check if the CharType of aCh is math or other symbol.
    */
diff --git a/intl/unicharutil/util/nsUnicharUtils.cpp b/intl/unicharutil/util/nsUnicharUtils.cpp
index 31ac06a52df6..913a27fa4344 100644
--- a/intl/unicharutil/util/nsUnicharUtils.cpp
+++ b/intl/unicharutil/util/nsUnicharUtils.cpp
@@ -520,6 +520,11 @@ bool IsSegmentBreakSkipChar(uint32_t u) {
          intl::UnicodeProperties::GetScriptCode(u) != intl::Script::HANGUL;
 }
 
+bool IsEastAsianPunctuation(uint32_t u) {
+  return intl::UnicodeProperties::IsEastAsianWidthFHW(u) &&
+         intl::UnicodeProperties::IsPunctuation(u);
+}
+
 bool IsPunctuationForWordSelect(char16_t aCh) {
   const uint8_t cat = unicode::GetGeneralCategory(aCh);
   switch (cat) {
diff --git a/intl/unicharutil/util/nsUnicharUtils.h b/intl/unicharutil/util/nsUnicharUtils.h
index 693e192e411f..9717be9938fa 100644
--- a/intl/unicharutil/util/nsUnicharUtils.h
+++ b/intl/unicharutil/util/nsUnicharUtils.h
@@ -153,7 +153,12 @@ namespace mozilla {
  */
 uint32_t HashUTF8AsUTF16(const char* aUTF8, size_t aLength, bool* aErr);
 
+/**
+ * Tests used in CSS Segment Break Transformation to determine whether a
+ * newline is discardable.
+ */
 bool IsSegmentBreakSkipChar(uint32_t u);
+bool IsEastAsianPunctuation(uint32_t u);
 
 /**
  * Return true for all Punctuation categories (Unicode general category P?),
diff --git a/layout/generic/nsTextFrame.cpp b/layout/generic/nsTextFrame.cpp
index d477df7443b1..77b65b6d13b8 100644
--- a/layout/generic/nsTextFrame.cpp
+++ b/layout/generic/nsTextFrame.cpp
@@ -1322,6 +1322,7 @@ BuildTextRunsScanner::FindBoundaryResult BuildTextRunsScanner::FindBoundaries(
     uint32_t start = textFrame->GetContentOffset();
     uint32_t length = textFrame->GetContentLength();
     const void* text;
+    const nsAtom* language = textFrame->StyleFont()->mLanguage;
     if (frag->Is2b()) {
       // It is possible that we may end up removing all whitespace in
       // a piece of text because of The White Space Processing Rules,
@@ -1336,7 +1337,7 @@ BuildTextRunsScanner::FindBoundaryResult BuildTextRunsScanner::FindBoundaries(
       char16_t* bufStart = aState->mBuffer.Elements();
       char16_t* bufEnd = nsTextFrameUtils::TransformText(
           frag->Get2b() + start, length, bufStart, compression, &incomingFlags,
-          &skipChars, &analysisFlags);
+          &skipChars, &analysisFlags, language);
       text = bufStart;
       length = bufEnd - bufStart;
     } else {
@@ -2318,6 +2319,7 @@ already_AddRefed<gfxTextRun> BuildTextRunsScanner::BuildTextRunForFrames(
     int32_t contentStart = mappedFlow->mStartFrame->GetContentOffset();
     int32_t contentEnd = mappedFlow->GetContentEnd();
     int32_t contentLength = contentEnd - contentStart;
+    const nsAtom* language = f->StyleFont()->mLanguage;
 
     TextRunMappedFlow* newFlow = &userMappedFlows[i];
     newFlow->mStartFrame = mappedFlow->mStartFrame;
@@ -2339,7 +2341,7 @@ already_AddRefed<gfxTextRun> BuildTextRunsScanner::BuildTextRunForFrames(
       char16_t* bufStart = static_cast<char16_t*>(aTextBuffer);
       char16_t* bufEnd = nsTextFrameUtils::TransformText(
           frag->Get2b() + contentStart, contentLength, bufStart, compression,
-          &mNextRunContextInfo, &skipChars, &analysisFlags);
+          &mNextRunContextInfo, &skipChars, &analysisFlags, language);
       aTextBuffer = bufEnd;
       currentTransformedTextOffset =
           bufEnd - static_cast<const char16_t*>(textPtr);
@@ -2356,7 +2358,7 @@ already_AddRefed<gfxTextRun> BuildTextRunsScanner::BuildTextRunForFrames(
         uint8_t* end = nsTextFrameUtils::TransformText(
             reinterpret_cast<const uint8_t*>(frag->Get1b()) + contentStart,
             contentLength, bufStart, compression, &mNextRunContextInfo,
-            &skipChars, &analysisFlags);
+            &skipChars, &analysisFlags, language);
         aTextBuffer =
             ExpandBuffer(static_cast<char16_t*>(aTextBuffer),
                          tempBuf.Elements(), end - tempBuf.Elements());
@@ -2367,7 +2369,7 @@ already_AddRefed<gfxTextRun> BuildTextRunsScanner::BuildTextRunForFrames(
         uint8_t* end = nsTextFrameUtils::TransformText(
             reinterpret_cast<const uint8_t*>(frag->Get1b()) + contentStart,
             contentLength, bufStart, compression, &mNextRunContextInfo,
-            &skipChars, &analysisFlags);
+            &skipChars, &analysisFlags, language);
         aTextBuffer = end;
         currentTransformedTextOffset =
             end - static_cast<const uint8_t*>(textPtr);
@@ -2618,6 +2620,7 @@ bool BuildTextRunsScanner::SetupLineBreakerContext(gfxTextRun* aTextRun) {
   }
 
   gfxSkipChars skipChars;
+  const nsAtom* language = mMappedFlows[0].mStartFrame->StyleFont()->mLanguage;
 
   for (uint32_t i = 0; i < mMappedFlows.Length(); ++i) {
     MappedFlow* mappedFlow = &mMappedFlows[i];
@@ -2639,7 +2642,7 @@ bool BuildTextRunsScanner::SetupLineBreakerContext(gfxTextRun* aTextRun) {
       char16_t* bufStart = static_cast<char16_t*>(textPtr);
       char16_t* bufEnd = nsTextFrameUtils::TransformText(
           frag->Get2b() + contentStart, contentLength, bufStart, compression,
-          &mNextRunContextInfo, &skipChars, &analysisFlags);
+          &mNextRunContextInfo, &skipChars, &analysisFlags, language);
       textPtr = bufEnd;
     } else {
       if (mDoubleByteText) {
@@ -2653,7 +2656,7 @@ bool BuildTextRunsScanner::SetupLineBreakerContext(gfxTextRun* aTextRun) {
         uint8_t* end = nsTextFrameUtils::TransformText(
             reinterpret_cast<const uint8_t*>(frag->Get1b()) + contentStart,
             contentLength, bufStart, compression, &mNextRunContextInfo,
-            &skipChars, &analysisFlags);
+            &skipChars, &analysisFlags, language);
         textPtr = ExpandBuffer(static_cast<char16_t*>(textPtr),
                                tempBuf.Elements(), end - tempBuf.Elements());
       } else {
@@ -2661,7 +2664,7 @@ bool BuildTextRunsScanner::SetupLineBreakerContext(gfxTextRun* aTextRun) {
         uint8_t* end = nsTextFrameUtils::TransformText(
             reinterpret_cast<const uint8_t*>(frag->Get1b()) + contentStart,
             contentLength, bufStart, compression, &mNextRunContextInfo,
-            &skipChars, &analysisFlags);
+            &skipChars, &analysisFlags, language);
         textPtr = end;
       }
     }
@@ -5371,7 +5374,7 @@ void nsTextFrame::UnionAdditionalOverflow(nsPresContext* aPresContext,
       nscoord topOrLeft(nscoord_MAX), bottomOrRight(nscoord_MIN);
       typedef gfxFont::Metrics Metrics;
       auto accumulateDecorationRect =
-          [&](const LineDecoration& dec, gfxFloat Metrics::*lineSize,
+          [&](const LineDecoration& dec, gfxFloat Metrics::* lineSize,
               mozilla::StyleTextDecorationLine lineType) {
             params.style = dec.mStyle;
             // If the style is solid, let's include decoration line rect of
@@ -7119,7 +7122,7 @@ void nsTextFrame::DrawTextRunAndDecorations(
 
   typedef gfxFont::Metrics Metrics;
   auto paintDecorationLine = [&](const LineDecoration& dec,
-                                 gfxFloat Metrics::*lineSize,
+                                 gfxFloat Metrics::* lineSize,
                                  StyleTextDecorationLine lineType) {
     if (dec.mStyle == StyleTextDecorationStyle::None) {
       return;
diff --git a/layout/generic/nsTextFrameUtils.cpp b/layout/generic/nsTextFrameUtils.cpp
index c6af6e7b04aa..05c9c40f6320 100644
--- a/layout/generic/nsTextFrameUtils.cpp
+++ b/layout/generic/nsTextFrameUtils.cpp
@@ -86,7 +86,8 @@ static CharT* TransformWhiteSpaces(
     const CharT* aText, uint32_t aLength, uint32_t aBegin, uint32_t aEnd,
     bool aHasSegmentBreak, bool& aInWhitespace, CharT* aOutput,
     nsTextFrameUtils::Flags& aFlags,
-    nsTextFrameUtils::CompressionMode aCompression, gfxSkipChars* aSkipChars) {
+    nsTextFrameUtils::CompressionMode aCompression, gfxSkipChars* aSkipChars,
+    bool aLangIsJapaneseOrChinese) {
   MOZ_ASSERT(aCompression == nsTextFrameUtils::COMPRESS_WHITESPACE ||
                  aCompression == nsTextFrameUtils::COMPRESS_WHITESPACE_NEWLINE,
              "whitespaces should be skippable!!");
@@ -126,10 +127,15 @@ static CharT* TransformWhiteSpaces(
       }
     } while (IsDefaultIgnorable(ucs4after) && pos < aLength);
 
-    // Discard newlines between characters that have F, W, or H
-    // EastAsianWidth property and neither side is Hangul.
+    // Discard newlines between characters that have F, W, or H EastAsianWidth
+    // property and neither side is Hangul.
+    // For Japanese/Chinese, also discard if *either* character is a fullwidth/
+    // wide punctuation character.
     isSegmentBreakSkippable =
-        IsSegmentBreakSkipChar(ucs4before) && IsSegmentBreakSkipChar(ucs4after);
+        (IsSegmentBreakSkipChar(ucs4before) &&
+         IsSegmentBreakSkipChar(ucs4after)) ||
+        (aLangIsJapaneseOrChinese && (IsEastAsianPunctuation(ucs4before) ||
+                                      IsEastAsianPunctuation(ucs4after)));
   }
 
   for (uint32_t i = aBegin; i < aEnd; ++i) {
@@ -201,12 +207,10 @@ static CharT* TransformWhiteSpaces(
 }
 
 template <class CharT>
-CharT* nsTextFrameUtils::TransformText(const CharT* aText, uint32_t aLength,
-                                       CharT* aOutput,
-                                       CompressionMode aCompression,
-                                       uint8_t* aIncomingFlags,
-                                       gfxSkipChars* aSkipChars,
-                                       Flags* aAnalysisFlags) {
+CharT* nsTextFrameUtils::TransformText(
+    const CharT* aText, uint32_t aLength, CharT* aOutput,
+    CompressionMode aCompression, uint8_t* aIncomingFlags,
+    gfxSkipChars* aSkipChars, Flags* aAnalysisFlags, const nsAtom* aLanguage) {
   Flags flags = Flags();
 #ifdef DEBUG
   int32_t skipCharsOffset = aSkipChars->GetOriginalCharCount();
@@ -247,6 +251,19 @@ CharT* nsTextFrameUtils::TransformText(const CharT* aText, uint32_t aLength,
     }
     *aIncomingFlags &= ~INCOMING_WHITESPACE;
   } else {
+    bool langIsJapaneseOrChinese = [=]() {
+      if (!aLanguage || aLanguage->GetLength() < 2) {
+        return false;
+      }
+      const char16_t* text = aLanguage->GetUTF16String();
+      if ((ToLowerCaseASCII(text[0]) == char16_t('j') &&
+           ToLowerCaseASCII(text[1]) == char16_t('a')) ||
+          (ToLowerCaseASCII(text[0]) == char16_t('z') &&
+           ToLowerCaseASCII(text[1]) == char16_t('h'))) {
+        return aLanguage->GetLength() == 2 || text[2] == '-';
+      }
+      return false;
+    }();
     bool inWhitespace = (*aIncomingFlags & INCOMING_WHITESPACE) != 0;
     uint32_t i;
     for (i = 0; i < aLength; ++i) {
@@ -284,9 +301,9 @@ CharT* nsTextFrameUtils::TransformText(const CharT* aText, uint32_t aLength,
           j--;
         }
         if (j > i) {
-          aOutput = TransformWhiteSpaces(aText, aLength, i, j, hasSegmentBreak,
-                                         inWhitespace, aOutput, flags,
-                                         aCompression, aSkipChars);
+          aOutput = TransformWhiteSpaces(
+              aText, aLength, i, j, hasSegmentBreak, inWhitespace, aOutput,
+              flags, aCompression, aSkipChars, langIsJapaneseOrChinese);
         }
         // We need to keep KeepChar()/SkipChar() in order, so process the
         // last white space first, then process the trailing discardables.
@@ -347,11 +364,11 @@ CharT* nsTextFrameUtils::TransformText(const CharT* aText, uint32_t aLength,
 template uint8_t* nsTextFrameUtils::TransformText(
     const uint8_t* aText, uint32_t aLength, uint8_t* aOutput,
     CompressionMode aCompression, uint8_t* aIncomingFlags,
-    gfxSkipChars* aSkipChars, Flags* aAnalysisFlags);
+    gfxSkipChars* aSkipChars, Flags* aAnalysisFlags, const nsAtom* aLanguage);
 template char16_t* nsTextFrameUtils::TransformText(
     const char16_t* aText, uint32_t aLength, char16_t* aOutput,
     CompressionMode aCompression, uint8_t* aIncomingFlags,
-    gfxSkipChars* aSkipChars, Flags* aAnalysisFlags);
+    gfxSkipChars* aSkipChars, Flags* aAnalysisFlags, const nsAtom* aLanguage);
 template bool nsTextFrameUtils::IsSkippableCharacterForTransformText(
     uint8_t aChar);
 template bool nsTextFrameUtils::IsSkippableCharacterForTransformText(
diff --git a/layout/generic/nsTextFrameUtils.h b/layout/generic/nsTextFrameUtils.h
index 5b9edf271e9c..6d77e7573c17 100644
--- a/layout/generic/nsTextFrameUtils.h
+++ b/layout/generic/nsTextFrameUtils.h
@@ -10,6 +10,7 @@
 #include "gfxSkipChars.h"
 #include "nsBidiUtils.h"
 
+class nsAtom;
 class nsIContent;
 struct nsStyleText;
 
@@ -121,12 +122,15 @@ class nsTextFrameUtils {
    * @param aIncomingFlags a flag indicating whether there was whitespace
    * or an Arabic character preceding this text. We set it to indicate if
    * there's an Arabic character or whitespace preceding the end of this text.
+   * @param aLanguage Content language (used to select Japanese/Chinese behavior
+   * at punctuation, see https://bugzilla.mozilla.org/show_bug.cgi?id=1935148).
    */
   template <class CharT>
   static CharT* TransformText(const CharT* aText, uint32_t aLength,
                               CharT* aOutput, CompressionMode aCompression,
                               uint8_t* aIncomingFlags, gfxSkipChars* aSkipChars,
-                              nsTextFrameUtils::Flags* aAnalysisFlags);
+                              nsTextFrameUtils::Flags* aAnalysisFlags,
+                              const nsAtom* aLanguage);
 
   /**
    * Returns whether aChar is a character that nsTextFrameUtils::TransformText
diff --git a/testing/web-platform/tests/css/css-text/line-breaking/segment-break-transformation-punctuation-001-ref.html b/testing/web-platform/tests/css/css-text/line-breaking/segment-break-transformation-punctuation-001-ref.html
new file mode 100644
index 000000000000..d339aebda9d2
--- /dev/null
+++ b/testing/web-platform/tests/css/css-text/line-breaking/segment-break-transformation-punctuation-001-ref.html
@@ -0,0 +1,7 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Segment break transformation: CJK punctuation</title>
+<link rel="author" href="mailto:jkew@mozilla.com">
+
+<p lang="ja">本システムはサポート切れのブラウザに対応しません。Internet Explorerをお使いの場合、Edge・Chrome・Firefoxなどに移行してください。(EdgeはChromium阪をお使いください)</p>
+<p lang="ja">ﾕｰｻﾞﾒｲ｢ｼﾞｮﾝ･ｽﾐｽ｣､ID｢smith｣ﾉｱｶｳﾝﾄｦｼｮｳｷｮｼﾏｽ｡y/N</p>
diff --git a/testing/web-platform/tests/css/css-text/line-breaking/segment-break-transformation-punctuation-001.html b/testing/web-platform/tests/css/css-text/line-breaking/segment-break-transformation-punctuation-001.html
new file mode 100644
index 000000000000..68e4589625db
--- /dev/null
+++ b/testing/web-platform/tests/css/css-text/line-breaking/segment-break-transformation-punctuation-001.html
@@ -0,0 +1,29 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Segment break transformation: CJK punctuation</title>
+<link rel="author" href="mailto:jkew@mozilla.com">
+<link rel="match" href="segment-break-transformation-punctuation-001-ref.html">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1935148">
+<meta name="flags" content="should" />
+
+<p lang="ja">
+  本システムはサポート切れのブラウザに対応しません。
+  Internet Explorerをお使いの場合、
+  Edge
+  ・
+  Chrome
+  ・
+  Firefoxなどに移行してください。
+  (EdgeはChromium阪をお使いください)
+</p>
+<p lang="ja">
+  ﾕｰｻﾞﾒｲ
+  ｢ｼﾞｮﾝ
+  ･
+  ｽﾐｽ｣
+  ､
+  ID
+  ｢smith｣
+  ﾉｱｶｳﾝﾄｦｼｮｳｷｮｼﾏｽ｡
+  y/N
+</p>