diff --git a/parser/html/javasrc/Tokenizer.java b/parser/html/javasrc/Tokenizer.java
index 6d7c34915573..0357cd015551 100644
--- a/parser/html/javasrc/Tokenizer.java
+++ b/parser/html/javasrc/Tokenizer.java
@@ -511,8 +511,6 @@ public class Tokenizer implements Locator, Locator2 {
 
     private boolean shouldSuspend;
 
-    private boolean keepBuffer;
-
     protected boolean confident;
 
     private int line;
@@ -572,7 +570,6 @@ public class Tokenizer implements Locator, Locator2 {
         this.systemIdentifier = null;
         this.attributes = null;
         this.shouldSuspend = false;
-        this.keepBuffer = false;
         this.confident = false;
         this.line = 0;
         // CPPONLY: this.attributeLine = 0;
@@ -635,7 +632,6 @@ public class Tokenizer implements Locator, Locator2 {
         // CPPONLY: this.attributes = tokenHandler.HasBuilder() ? new HtmlAttributes(mappingLangToXmlLang) : null;
         // CPPONLY: this.newAttributesEachTime = !tokenHandler.HasBuilder();
         this.shouldSuspend = false;
-        this.keepBuffer = false;
         this.confident = false;
         this.line = 0;
         // CPPONLY: this.attributeLine = 0;
@@ -657,18 +653,6 @@ public class Tokenizer implements Locator, Locator2 {
     // CPPONLY: return viewingXmlSource;
     // CPPONLY: }
 
-    public void setKeepBuffer(boolean keepBuffer) {
-        this.keepBuffer = keepBuffer;
-    }
-
-    public boolean dropBufferIfLongerThan(int length) {
-        if (strBuf.length > length) {
-            strBuf = null;
-            return true;
-        }
-        return false;
-    }
-
     // [NOCPP[
 
     /**
@@ -7241,9 +7225,7 @@ public class Tokenizer implements Locator, Locator2 {
     }
 
     public void end() throws SAXException {
-        if (!keepBuffer) {
-            strBuf = null;
-        }
+        strBuf = null;
         doctypeName = null;
         if (systemIdentifier != null) {
             Portability.releaseString(systemIdentifier);
@@ -7433,9 +7415,7 @@ public class Tokenizer implements Locator, Locator2 {
 
     public void initializeWithoutStarting() throws SAXException {
         confident = false;
-        if (!keepBuffer) {
-            strBuf = null;
-        }
+        strBuf = null;
         line = 1;
         // CPPONLY: attributeLine = 1;
         // [NOCPP[
diff --git a/parser/html/javasrc/TreeBuilder.java b/parser/html/javasrc/TreeBuilder.java
index c190b7fd2020..f7b70ee0dada 100644
--- a/parser/html/javasrc/TreeBuilder.java
+++ b/parser/html/javasrc/TreeBuilder.java
@@ -436,8 +436,6 @@ public abstract class TreeBuilder<T> implements TokenHandler,
 
     private boolean allowDeclarativeShadowRoots = false;
 
-    private boolean keepBuffer = false;
-
     // [NOCPP[
 
     private boolean reportingDoctype = true;
@@ -579,18 +577,6 @@ public abstract class TreeBuilder<T> implements TokenHandler,
 
     // ]NOCPP]
 
-    public void setKeepBuffer(boolean keepBuffer) {
-        this.keepBuffer = keepBuffer;
-    }
-
-    public boolean dropBufferIfLongerThan(int length) {
-        if (charBuffer.length > length) {
-            charBuffer = null;
-            return true;
-        }
-        return false;
-    }
-
     @SuppressWarnings("unchecked") public final void startTokenization(Tokenizer self) throws SAXException {
         tokenizer = self;
         stackNodes = new StackNode[64];
@@ -612,9 +598,7 @@ public abstract class TreeBuilder<T> implements TokenHandler,
         // ]NOCPP]
         start(fragment);
         charBufferLen = 0;
-        if (!keepBuffer) {
-            charBuffer = null;
-        }
+        charBuffer = null;
         framesetOk = true;
         if (fragment) {
             T elt;
@@ -1467,10 +1451,7 @@ public abstract class TreeBuilder<T> implements TokenHandler,
         // [NOCPP[
         idLocations.clear();
         // ]NOCPP]
-
-        if (!keepBuffer) {
-            charBuffer = null;
-        }
+        charBuffer = null;
         end();
     }
 
diff --git a/parser/html/nsHtml5StringParser.cpp b/parser/html/nsHtml5StringParser.cpp
index 69e2806ce5eb..5fe2b2e323cb 100644
--- a/parser/html/nsHtml5StringParser.cpp
+++ b/parser/html/nsHtml5StringParser.cpp
@@ -20,11 +20,9 @@ nsHtml5StringParser::nsHtml5StringParser()
       mTreeBuilder(new nsHtml5TreeBuilder(mBuilder)),
       mTokenizer(new nsHtml5Tokenizer(mTreeBuilder.get(), false)) {
   mTokenizer->setInterner(&mAtomTable);
-  mTokenizer->setKeepBuffer(true);
-  mTreeBuilder->setKeepBuffer(true);
 }
 
-nsHtml5StringParser::~nsHtml5StringParser() { ClearCaches(); }
+nsHtml5StringParser::~nsHtml5StringParser() {}
 
 nsresult nsHtml5StringParser::ParseFragment(
     const nsAString& aSourceBuffer, nsIContent* aTargetNode,
@@ -71,31 +69,6 @@ nsresult nsHtml5StringParser::ParseDocument(
                   aTargetDoc->AllowsDeclarativeShadowRoots());
 }
 
-void nsHtml5StringParser::ClearCaches() {
-  mTokenizer->dropBufferIfLongerThan(0);
-  mTreeBuilder->dropBufferIfLongerThan(0);
-  if (mCacheClearer) {
-    mCacheClearer->Disconnect();
-    mCacheClearer = nullptr;
-  }
-}
-
-void nsHtml5StringParser::TryCache() {
-  const int32_t kMaxBuffer = 1024 * 1024;
-  bool didDrop = mTokenizer->dropBufferIfLongerThan(kMaxBuffer);
-  didDrop |= mTreeBuilder->dropBufferIfLongerThan(kMaxBuffer);
-  if (didDrop) {
-    return;
-  }
-
-  if (!mCacheClearer) {
-    mCacheClearer = new CacheClearer(this);
-    nsCOMPtr<nsIRunnable> runnable = mCacheClearer.get();
-    NS_DispatchToMainThreadQueue(runnable.forget(),
-                                 mozilla::EventQueuePriority::Idle);
-  }
-}
-
 nsresult nsHtml5StringParser::Tokenize(const nsAString& aSourceBuffer,
                                        Document* aDocument,
                                        bool aScriptingEnabledForNoscriptParsing,
@@ -136,10 +109,8 @@ nsresult nsHtml5StringParser::Tokenize(const nsAString& aSourceBuffer,
   if (NS_SUCCEEDED(rv)) {
     mTokenizer->eof();
   }
-
   mTokenizer->end();
   mBuilder->Finish();
   mAtomTable.Clear();
-  TryCache();
   return rv;
 }
diff --git a/parser/html/nsHtml5StringParser.h b/parser/html/nsHtml5StringParser.h
index 8b0203301dc5..1d4140484137 100644
--- a/parser/html/nsHtml5StringParser.h
+++ b/parser/html/nsHtml5StringParser.h
@@ -67,9 +67,6 @@ class nsHtml5StringParser : public nsParserBase {
                     bool aScriptingEnabledForNoscriptParsing,
                     bool aDeclarativeShadowRootsAllowed);
 
-  void TryCache();
-  void ClearCaches();
-
   /**
    * The tree operation executor
    */
@@ -89,24 +86,6 @@ class nsHtml5StringParser : public nsParserBase {
    * The scoped atom table
    */
   nsHtml5AtomTable mAtomTable;
-
-  class CacheClearer : public mozilla::Runnable {
-   public:
-    explicit CacheClearer(nsHtml5StringParser* aParser)
-        : Runnable("CacheClearer"), mParser(aParser) {}
-    NS_IMETHOD Run() {
-      if (mParser) {
-        mParser->ClearCaches();
-      }
-      return NS_OK;
-    }
-    void Disconnect() { mParser = nullptr; }
-
-   private:
-    nsHtml5StringParser* mParser;
-  };
-
-  RefPtr<CacheClearer> mCacheClearer;
 };
 
 #endif  // nsHtml5StringParser_h
diff --git a/parser/html/nsHtml5Tokenizer.cpp b/parser/html/nsHtml5Tokenizer.cpp
index 127c0a77fc72..5092bf4bf67b 100644
--- a/parser/html/nsHtml5Tokenizer.cpp
+++ b/parser/html/nsHtml5Tokenizer.cpp
@@ -126,7 +126,6 @@ nsHtml5Tokenizer::nsHtml5Tokenizer(nsHtml5TreeBuilder* tokenHandler,
                                             : nullptr),
       newAttributesEachTime(!tokenHandler->HasBuilder()),
       shouldSuspend(false),
-      keepBuffer(false),
       confident(false),
       line(0),
       attributeLine(0),
@@ -147,18 +146,6 @@ void nsHtml5Tokenizer::initLocation(nsHtml5String newPublicId,
 
 bool nsHtml5Tokenizer::isViewingXmlSource() { return viewingXmlSource; }
 
-void nsHtml5Tokenizer::setKeepBuffer(bool keepBuffer) {
-  this->keepBuffer = keepBuffer;
-}
-
-bool nsHtml5Tokenizer::dropBufferIfLongerThan(int32_t length) {
-  if (strBuf.length > length) {
-    strBuf = nullptr;
-    return true;
-  }
-  return false;
-}
-
 void nsHtml5Tokenizer::setState(int32_t specialTokenizerState) {
   this->stateSave = specialTokenizerState;
   this->endTagExpectation = nullptr;
@@ -5035,9 +5022,7 @@ void nsHtml5Tokenizer::emitOrAppendOne(const char16_t* val,
 }
 
 void nsHtml5Tokenizer::end() {
-  if (!keepBuffer) {
-    strBuf = nullptr;
-  }
+  strBuf = nullptr;
   doctypeName = nullptr;
   if (systemIdentifier) {
     systemIdentifier.Release();
@@ -5163,9 +5148,7 @@ void nsHtml5Tokenizer::loadState(nsHtml5Tokenizer* other) {
 
 void nsHtml5Tokenizer::initializeWithoutStarting() {
   confident = false;
-  if (!keepBuffer) {
-    strBuf = nullptr;
-  }
+  strBuf = nullptr;
   line = 1;
   attributeLine = 1;
   resetToDataState();
diff --git a/parser/html/nsHtml5Tokenizer.h b/parser/html/nsHtml5Tokenizer.h
index e19570ca3f9a..91c70fc4120b 100644
--- a/parser/html/nsHtml5Tokenizer.h
+++ b/parser/html/nsHtml5Tokenizer.h
@@ -308,7 +308,6 @@ class nsHtml5Tokenizer {
   nsHtml5HtmlAttributes* attributes;
   bool newAttributesEachTime;
   bool shouldSuspend;
-  bool keepBuffer;
 
  protected:
   bool confident;
@@ -324,8 +323,6 @@ class nsHtml5Tokenizer {
   void setInterner(nsHtml5AtomTable* interner);
   void initLocation(nsHtml5String newPublicId, nsHtml5String newSystemId);
   bool isViewingXmlSource();
-  void setKeepBuffer(bool keepBuffer);
-  bool dropBufferIfLongerThan(int32_t length);
   void setState(int32_t specialTokenizerState);
   void setStateAndEndTagExpectation(int32_t specialTokenizerState,
                                     nsHtml5ElementName* endTagExpectation);
diff --git a/parser/html/nsHtml5TreeBuilder.cpp b/parser/html/nsHtml5TreeBuilder.cpp
index 9ef9a519f7cc..26db77865fbc 100644
--- a/parser/html/nsHtml5TreeBuilder.cpp
+++ b/parser/html/nsHtml5TreeBuilder.cpp
@@ -100,18 +100,6 @@ static const char* const QUIRKY_PUBLIC_IDS_DATA[] = {
     "-//webtechs//dtd mozilla html//"};
 staticJArray<const char*, int32_t> nsHtml5TreeBuilder::QUIRKY_PUBLIC_IDS = {
     QUIRKY_PUBLIC_IDS_DATA, MOZ_ARRAY_LENGTH(QUIRKY_PUBLIC_IDS_DATA)};
-void nsHtml5TreeBuilder::setKeepBuffer(bool keepBuffer) {
-  this->keepBuffer = keepBuffer;
-}
-
-bool nsHtml5TreeBuilder::dropBufferIfLongerThan(int32_t length) {
-  if (charBuffer.length > length) {
-    charBuffer = nullptr;
-    return true;
-  }
-  return false;
-}
-
 void nsHtml5TreeBuilder::startTokenization(nsHtml5Tokenizer* self) {
   tokenizer = self;
   stackNodes = jArray<nsHtml5StackNode*, int32_t>::newJArray(64);
@@ -130,9 +118,7 @@ void nsHtml5TreeBuilder::startTokenization(nsHtml5Tokenizer* self) {
   headPointer = nullptr;
   start(fragment);
   charBufferLen = 0;
-  if (!keepBuffer) {
-    charBuffer = nullptr;
-  }
+  charBuffer = nullptr;
   framesetOk = true;
   if (fragment) {
     nsIContentHandle* elt;
@@ -666,9 +652,7 @@ void nsHtml5TreeBuilder::endTokenization() {
     stackNodesIdx = 0;
     stackNodes = nullptr;
   }
-  if (!keepBuffer) {
-    charBuffer = nullptr;
-  }
+  charBuffer = nullptr;
   end();
 }
 
diff --git a/parser/html/nsHtml5TreeBuilder.h b/parser/html/nsHtml5TreeBuilder.h
index b48902df355b..d6c4828e7cf9 100644
--- a/parser/html/nsHtml5TreeBuilder.h
+++ b/parser/html/nsHtml5TreeBuilder.h
@@ -315,7 +315,6 @@ class nsHtml5TreeBuilder : public nsAHtml5TreeBuilderState {
   bool quirks;
   bool forceNoQuirks;
   bool allowDeclarativeShadowRoots;
-  bool keepBuffer;
   inline nsHtml5ContentCreatorFunction htmlCreator(
       mozilla::dom::HTMLContentCreatorFunction htmlCreator) {
     nsHtml5ContentCreatorFunction creator;
@@ -331,8 +330,6 @@ class nsHtml5TreeBuilder : public nsAHtml5TreeBuilderState {
   }
 
  public:
-  void setKeepBuffer(bool keepBuffer);
-  bool dropBufferIfLongerThan(int32_t length);
   void startTokenization(nsHtml5Tokenizer* self);
   void doctype(nsAtom* name, nsHtml5String publicIdentifier,
                nsHtml5String systemIdentifier, bool forceQuirks);
diff --git a/parser/html/nsHtml5TreeBuilderCppSupplement.h b/parser/html/nsHtml5TreeBuilderCppSupplement.h
index be2898157bef..59df6937e295 100644
--- a/parser/html/nsHtml5TreeBuilderCppSupplement.h
+++ b/parser/html/nsHtml5TreeBuilderCppSupplement.h
@@ -42,7 +42,6 @@ nsHtml5TreeBuilder::nsHtml5TreeBuilder(nsHtml5OplessBuilder* aBuilder)
       quirks(false),
       forceNoQuirks(false),
       allowDeclarativeShadowRoots(false),
-      keepBuffer(false),
       mBuilder(aBuilder),
       mViewSource(nullptr),
       mOpSink(nullptr),