diff --git a/parser/expat/expat_config.h b/parser/expat/expat_config.h
index d302adceb92f..be284197f041 100644
--- a/parser/expat/expat_config.h
+++ b/parser/expat/expat_config.h
@@ -17,7 +17,10 @@
 
 #define XMLCALL
 #define XML_STATIC
-#define XMLIMPORT
+#ifdef HAVE_VISIBILITY_HIDDEN_ATTRIBUTE
+#  undef XMLIMPORT
+#  define XMLIMPORT __attribute__((visibility("hidden")))
+#endif
 
 #define XML_UNICODE
 typedef char XML_LChar;
@@ -37,112 +40,4 @@ typedef uint16_t XML_Char;
 #define XML_DTD
 #define XML_NS
 
-/* avoid conflicts with system version of libexpat */
-
-/* expat.h */
-#define XML_SetElementDeclHandler MOZ_XML_SetElementDeclHandler
-#define XML_SetAttlistDeclHandler MOZ_XML_SetAttlistDeclHandler
-#define XML_SetXmlDeclHandler MOZ_XML_SetXmlDeclHandler
-#define XML_ParserCreate MOZ_XML_ParserCreate
-#define XML_ParserCreateNS MOZ_XML_ParserCreateNS
-#define XML_ParserCreate_MM MOZ_XML_ParserCreate_MM
-#define XML_ParserReset MOZ_XML_ParserReset
-#define XML_SetEntityDeclHandler MOZ_XML_SetEntityDeclHandler
-#define XML_SetElementHandler MOZ_XML_SetElementHandler
-#define XML_SetStartElementHandler MOZ_XML_SetStartElementHandler
-#define XML_SetEndElementHandler MOZ_XML_SetEndElementHandler
-#define XML_SetCharacterDataHandler MOZ_XML_SetCharacterDataHandler
-#ifndef __VMS
-#define XML_SetProcessingInstructionHandler MOZ_XML_SetProcessingInstructionHandler
-#else
-#define XML_SetProcessingInstrHandler MOZ_XML_SetProcessingInstrHandler
-#endif
-#define XML_SetCommentHandler MOZ_XML_SetCommentHandler
-#define XML_SetCdataSectionHandler MOZ_XML_SetCdataSectionHandler
-#define XML_SetStartCdataSectionHandler MOZ_XML_SetStartCdataSectionHandler
-#define XML_SetEndCdataSectionHandler MOZ_XML_SetEndCdataSectionHandler
-#define XML_SetDefaultHandler MOZ_XML_SetDefaultHandler
-#define XML_SetDefaultHandlerExpand MOZ_XML_SetDefaultHandlerExpand
-#define XML_SetDoctypeDeclHandler MOZ_XML_SetDoctypeDeclHandler
-#define XML_SetStartDoctypeDeclHandler MOZ_XML_SetStartDoctypeDeclHandler
-#define XML_SetEndDoctypeDeclHandler MOZ_XML_SetEndDoctypeDeclHandler
-#ifndef __VMS
-#define XML_SetUnparsedEntityDeclHandler MOZ_XML_SetUnparsedEntityDeclHandler
-#else
-#define XML_SetUnparsedEntDeclHandler MOZ_XML_SetUnparsedEntDeclHandler
-#endif
-#define XML_SetNotationDeclHandler MOZ_XML_SetNotationDeclHandler
-#define XML_SetNamespaceDeclHandler MOZ_XML_SetNamespaceDeclHandler
-#ifndef __VMS
-#define XML_SetStartNamespaceDeclHandler MOZ_XML_SetStartNamespaceDeclHandler
-#else
-#define XML_SetStartNamespcDeclHandler MOZ_XML_SetStartNamespcDeclHandler
-#endif
-#define XML_SetEndNamespaceDeclHandler MOZ_XML_SetEndNamespaceDeclHandler
-#define XML_SetNotStandaloneHandler MOZ_XML_SetNotStandaloneHandler
-#define XML_SetExternalEntityRefHandler MOZ_XML_SetExternalEntityRefHandler
-#ifndef __VMS
-#define XML_SetExternalEntityRefHandlerArg MOZ_XML_SetExternalEntityRefHandlerArg
-#else
-#define XML_SetExternalEntRefHandlerArg MOZ_XML_SetExternalEntRefHandlerArg
-#endif
-#define XML_SetSkippedEntityHandler MOZ_XML_SetSkippedEntityHandler
-#define XML_SetUnknownEncodingHandler MOZ_XML_SetUnknownEncodingHandler
-#define XML_DefaultCurrent MOZ_XML_DefaultCurrent
-#define XML_SetReturnNSTriplet MOZ_XML_SetReturnNSTriplet
-#define XML_SetUserData MOZ_XML_SetUserData
-#define XML_SetEncoding MOZ_XML_SetEncoding
-#define XML_UseParserAsHandlerArg MOZ_XML_UseParserAsHandlerArg
-#define XML_UseForeignDTD MOZ_XML_UseForeignDTD
-#define XML_SetBase MOZ_XML_SetBase
-#define XML_GetBase MOZ_XML_GetBase
-#define XML_GetSpecifiedAttributeCount MOZ_XML_GetSpecifiedAttributeCount
-#define XML_GetIdAttributeIndex MOZ_XML_GetIdAttributeIndex
-#define XML_Parse MOZ_XML_Parse
-#define XML_GetBuffer MOZ_XML_GetBuffer
-#define XML_ParseBuffer MOZ_XML_ParseBuffer
-#define XML_StopParser MOZ_XML_StopParser
-#define XML_ResumeParser MOZ_XML_ResumeParser
-#define XML_GetParsingStatus MOZ_XML_GetParsingStatus
-#define XML_ExternalEntityParserCreate MOZ_XML_ExternalEntityParserCreate
-#define XML_SetParamEntityParsing MOZ_XML_SetParamEntityParsing
-#define XML_GetErrorCode MOZ_XML_GetErrorCode
-#define XML_GetCurrentLineNumber MOZ_XML_GetCurrentLineNumber
-#define XML_GetCurrentColumnNumber MOZ_XML_GetCurrentColumnNumber
-#define XML_GetCurrentByteIndex MOZ_XML_GetCurrentByteIndex
-#define XML_GetCurrentByteCount MOZ_XML_GetCurrentByteCount
-#define XML_GetInputContext MOZ_XML_GetInputContext
-#define XML_FreeContentModel MOZ_XML_FreeContentModel
-#define XML_MemMalloc MOZ_XML_MemMalloc
-#define XML_MemRealloc MOZ_XML_MemRealloc
-#define XML_MemFree MOZ_XML_MemFree
-#define XML_ParserFree MOZ_XML_ParserFree
-#define XML_ErrorString MOZ_XML_ErrorString
-#define XML_ExpatVersion MOZ_XML_ExpatVersion
-#define XML_ExpatVersionInfo MOZ_XML_ExpatVersionInfo
-#define XML_GetFeatureList MOZ_XML_GetFeatureList
-
-/* xmlrole.h */
-#define XmlPrologStateInit MOZ_XmlPrologStateInit
-#ifndef __VMS
-#define XmlPrologStateInitExternalEntity MOZ_XmlPrologStateInitExternalEntity
-#else
-#define XmlPrologStateInitExternalEnt MOZ_XmlPrologStateInitExternalEnt
-#endif
-
-/* xmltok.h */
-#define XmlParseXmlDecl MOZ_XmlParseXmlDecl
-#define XmlParseXmlDeclNS MOZ_XmlParseXmlDeclNS
-#define XmlInitEncoding MOZ_XmlInitEncoding
-#define XmlInitEncodingNS MOZ_XmlInitEncodingNS
-#define XmlGetUtf8InternalEncoding MOZ_XmlGetUtf8InternalEncoding
-#define XmlGetUtf16InternalEncoding MOZ_XmlGetUtf16InternalEncoding
-#define XmlGetUtf8InternalEncodingNS MOZ_XmlGetUtf8InternalEncodingNS
-#define XmlGetUtf16InternalEncodingNS MOZ_XmlGetUtf16InternalEncodingNS
-#define XmlUtf8Encode MOZ_XmlUtf8Encode
-#define XmlUtf16Encode MOZ_XmlUtf16Encode
-#define XmlSizeOfUnknownEncoding MOZ_XmlSizeOfUnknownEncoding
-#define XmlInitUnknownEncoding MOZ_XmlInitUnknownEncoding
-#define XmlInitUnknownEncodingNS MOZ_XmlInitUnknownEncodingNS
-
 #endif /* __expat_config_h__ */
diff --git a/parser/expat/lib/expat.h b/parser/expat/lib/expat.h
index a3788a6902a9..bb72c6bb12ff 100644
--- a/parser/expat/lib/expat.h
+++ b/parser/expat/lib/expat.h
@@ -820,13 +820,7 @@ XML_ParseBuffer(XML_Parser parser, int len, int isFinal);
    When suspended, parsing can be resumed by calling XML_ResumeParser(). 
 */
 XMLPARSEAPI(enum XML_Status)
-/* BEGIN MOZILLA CHANGE (Bug 1743007 - Convert expat XML_StopParser API to take an int param instead of u8) */
-#if 0
 XML_StopParser(XML_Parser parser, XML_Bool resumable);
-#else
-XML_StopParser(XML_Parser parser, int resumable);
-#endif
-/* END MOZILLA CHANGE */
 
 /* Resumes parsing after it has been suspended with XML_StopParser().
    Must not be called from within a handler call-back. Returns same
@@ -1058,16 +1052,6 @@ XML_GetFeatureList(void);
 #define XML_MINOR_VERSION 2
 #define XML_MICRO_VERSION 1
 
-/* BEGIN MOZILLA CHANGE (Report opening tag of mismatched closing tag) */
-XMLPARSEAPI(const XML_Char*)
-MOZ_XML_GetMismatchedTag(XML_Parser parser);
-/* END MOZILLA CHANGE */
-
-/* BEGIN MOZILLA CHANGE (Report whether the parser is currently expanding an entity) */
-XMLPARSEAPI(XML_Bool)
-MOZ_XML_ProcessingEntityValue(XML_Parser parser);
-/* END MOZILLA CHANGE */
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/parser/expat/lib/moz.build b/parser/expat/lib/moz.build
index beaf8459b979..817674ceeede 100644
--- a/parser/expat/lib/moz.build
+++ b/parser/expat/lib/moz.build
@@ -9,12 +9,11 @@ include("sources.mozbuild")
 EXPORTS += [
     'expat.h',
     'expat_external.h',
+    'moz_expat.h',
 ]
 
 if CONFIG["MOZ_WASM_SANDBOXING_EXPAT"]:
-    # Ideally we'd only build moz_extensions.c, but it's currently included
-    # from xmltok.c because it uses a lot of its internals.
-    SOURCES += ['xmltok.c']
+    SOURCES += ['moz_xmltok.c']
 else:
     SOURCES += expat_sources
 
diff --git a/parser/expat/lib/moz_expat.h b/parser/expat/lib/moz_expat.h
new file mode 100644
index 000000000000..797c4853d23e
--- /dev/null
+++ b/parser/expat/lib/moz_expat.h
@@ -0,0 +1,114 @@
+/* -*- Mode: C; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 MOZ_EXPAT_H_
+#define MOZ_EXPAT_H_
+
+#include "expat_config.h"
+#include "expat.h"
+#include "mozilla/Types.h"
+
+MOZ_BEGIN_EXTERN_C
+
+void
+MOZ_XML_SetXmlDeclHandler(XML_Parser parser,
+                          XML_XmlDeclHandler xmldecl);
+
+XML_Parser
+MOZ_XML_ParserCreate_MM(const XML_Char *encoding,
+                        const XML_Memory_Handling_Suite *memsuite,
+                        const XML_Char *namespaceSeparator);
+
+void
+MOZ_XML_SetElementHandler(XML_Parser parser,
+                          XML_StartElementHandler start,
+                          XML_EndElementHandler end);
+
+void
+MOZ_XML_SetCharacterDataHandler(XML_Parser parser,
+                                XML_CharacterDataHandler handler);
+
+void
+MOZ_XML_SetProcessingInstructionHandler(XML_Parser parser,
+                                        XML_ProcessingInstructionHandler handler);
+
+void
+MOZ_XML_SetCommentHandler(XML_Parser parser,
+                          XML_CommentHandler handler);
+
+void
+MOZ_XML_SetCdataSectionHandler(XML_Parser parser,
+                               XML_StartCdataSectionHandler start,
+                               XML_EndCdataSectionHandler end);
+
+void
+MOZ_XML_SetDefaultHandlerExpand(XML_Parser parser,
+                                XML_DefaultHandler handler);
+
+void
+MOZ_XML_SetDoctypeDeclHandler(XML_Parser parser,
+                              XML_StartDoctypeDeclHandler start,
+                              XML_EndDoctypeDeclHandler end);
+
+void
+MOZ_XML_SetExternalEntityRefHandler(XML_Parser parser,
+                                    XML_ExternalEntityRefHandler handler);
+
+void
+MOZ_XML_SetReturnNSTriplet(XML_Parser parser, int do_nst);
+
+enum XML_Status
+MOZ_XML_SetBase(XML_Parser parser, const XML_Char *base);
+
+const XML_Char *
+MOZ_XML_GetBase(XML_Parser parser);
+
+int
+MOZ_XML_GetSpecifiedAttributeCount(XML_Parser parser);
+
+enum XML_Status
+MOZ_XML_Parse(XML_Parser parser, const char *s, int len, int isFinal);
+
+enum XML_Status
+MOZ_XML_StopParser(XML_Parser parser, int resumable);
+
+enum XML_Status
+MOZ_XML_ResumeParser(XML_Parser parser);
+
+XML_Parser
+MOZ_XML_ExternalEntityParserCreate(XML_Parser parser,
+                                   const XML_Char *context,
+                                   const XML_Char *encoding);
+
+int
+MOZ_XML_SetParamEntityParsing(XML_Parser parser,
+                              enum XML_ParamEntityParsing parsing);
+
+int
+MOZ_XML_SetHashSalt(XML_Parser parser, unsigned long hash_salt);
+
+enum XML_Error
+MOZ_XML_GetErrorCode(XML_Parser parser);
+
+XML_Size MOZ_XML_GetCurrentLineNumber(XML_Parser parser);
+
+XML_Size MOZ_XML_GetCurrentColumnNumber(XML_Parser parser);
+
+XML_Index MOZ_XML_GetCurrentByteIndex(XML_Parser parser);
+
+void
+MOZ_XML_ParserFree(XML_Parser parser);
+
+// Mozilla-only API: Report opening tag of mismatched closing tag.
+const XML_Char*
+MOZ_XML_GetMismatchedTag(XML_Parser parser);
+
+// Mozilla-only API: Report whether the parser is currently expanding an entity.
+XML_Bool
+MOZ_XML_ProcessingEntityValue(XML_Parser parser);
+
+MOZ_END_EXTERN_C
+
+#endif /* MOZ_EXPAT_H_ */
diff --git a/parser/expat/lib/moz_xmlparse.c b/parser/expat/lib/moz_xmlparse.c
new file mode 100644
index 000000000000..2d75f62a4f52
--- /dev/null
+++ b/parser/expat/lib/moz_xmlparse.c
@@ -0,0 +1,147 @@
+/* -*- Mode: C; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 "moz_expat.h"
+#include "xmlparse.c"
+
+void
+MOZ_XML_SetXmlDeclHandler(XML_Parser parser,
+                          XML_XmlDeclHandler xmldecl) {
+  return XML_SetXmlDeclHandler(parser, xmldecl);
+}
+
+XML_Parser
+MOZ_XML_ParserCreate_MM(const XML_Char *encoding,
+                        const XML_Memory_Handling_Suite *memsuite,
+                        const XML_Char *namespaceSeparator) {
+  return XML_ParserCreate_MM(encoding, memsuite, namespaceSeparator);
+}
+
+void
+MOZ_XML_SetElementHandler(XML_Parser parser,
+                          XML_StartElementHandler start,
+                          XML_EndElementHandler end) {
+  XML_SetElementHandler(parser, start, end);
+}
+
+void
+MOZ_XML_SetCharacterDataHandler(XML_Parser parser,
+                                XML_CharacterDataHandler handler) {
+  return XML_SetCharacterDataHandler(parser, handler);
+}
+
+void
+MOZ_XML_SetProcessingInstructionHandler(XML_Parser parser,
+                                        XML_ProcessingInstructionHandler handler) {
+  return XML_SetProcessingInstructionHandler(parser, handler);
+}
+
+void
+MOZ_XML_SetCommentHandler(XML_Parser parser,
+                          XML_CommentHandler handler) {
+  XML_SetCommentHandler(parser, handler);
+}
+
+void
+MOZ_XML_SetCdataSectionHandler(XML_Parser parser,
+                               XML_StartCdataSectionHandler start,
+                               XML_EndCdataSectionHandler end) {
+  XML_SetCdataSectionHandler(parser, start, end);
+}
+
+void
+MOZ_XML_SetDefaultHandlerExpand(XML_Parser parser,
+                                XML_DefaultHandler handler) {
+  XML_SetDefaultHandlerExpand(parser, handler);
+}
+
+void
+MOZ_XML_SetDoctypeDeclHandler(XML_Parser parser,
+                              XML_StartDoctypeDeclHandler start,
+                              XML_EndDoctypeDeclHandler end) {
+  XML_SetDoctypeDeclHandler(parser, start, end);
+}
+
+void
+MOZ_XML_SetExternalEntityRefHandler(XML_Parser parser,
+                                    XML_ExternalEntityRefHandler handler) {
+  XML_SetExternalEntityRefHandler(parser, handler);
+}
+
+void
+MOZ_XML_SetReturnNSTriplet(XML_Parser parser, int do_nst) {
+  XML_SetReturnNSTriplet(parser, do_nst);
+}
+
+enum XML_Status
+MOZ_XML_SetBase(XML_Parser parser, const XML_Char *base) {
+  return XML_SetBase(parser, base);
+}
+
+const XML_Char *
+MOZ_XML_GetBase(XML_Parser parser) {
+  return XML_GetBase(parser);
+}
+
+int
+MOZ_XML_GetSpecifiedAttributeCount(XML_Parser parser) {
+  return XML_GetSpecifiedAttributeCount(parser);
+}
+
+enum XML_Status
+MOZ_XML_Parse(XML_Parser parser, const char *s, int len, int isFinal) {
+  return XML_Parse(parser, s, len, isFinal);
+}
+
+enum XML_Status
+MOZ_XML_StopParser(XML_Parser parser, int resumable) {
+  return XML_StopParser(parser, resumable);
+}
+
+enum XML_Status
+MOZ_XML_ResumeParser(XML_Parser parser) {
+  return XML_ResumeParser(parser);
+}
+
+XML_Parser
+MOZ_XML_ExternalEntityParserCreate(XML_Parser parser,
+                                   const XML_Char *context,
+                                   const XML_Char *encoding) {
+  return XML_ExternalEntityParserCreate(parser, context, encoding);
+}
+
+int
+MOZ_XML_SetParamEntityParsing(XML_Parser parser,
+                              enum XML_ParamEntityParsing parsing) {
+  return XML_SetParamEntityParsing(parser, parsing);
+}
+
+int
+MOZ_XML_SetHashSalt(XML_Parser parser, unsigned long hash_salt) {
+  return XML_SetHashSalt(parser, hash_salt);
+}
+
+enum XML_Error
+MOZ_XML_GetErrorCode(XML_Parser parser)
+{
+  return XML_GetErrorCode(parser);
+}
+
+XML_Size MOZ_XML_GetCurrentLineNumber(XML_Parser parser) {
+  return XML_GetCurrentLineNumber(parser);
+}
+
+XML_Size MOZ_XML_GetCurrentColumnNumber(XML_Parser parser) {
+  return XML_GetCurrentColumnNumber(parser);
+}
+
+XML_Index MOZ_XML_GetCurrentByteIndex(XML_Parser parser) {
+  return XML_GetCurrentByteIndex(parser);
+}
+
+void
+MOZ_XML_ParserFree(XML_Parser parser) {
+  return XML_ParserFree(parser);
+}
diff --git a/parser/expat/lib/moz_extensions.c b/parser/expat/lib/moz_xmltok.c
similarity index 99%
rename from parser/expat/lib/moz_extensions.c
rename to parser/expat/lib/moz_xmltok.c
index 37b9e7f71e71..a10ab916d18a 100644
--- a/parser/expat/lib/moz_extensions.c
+++ b/parser/expat/lib/moz_xmltok.c
@@ -3,6 +3,8 @@
  * 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/. */
 
+#include "xmltok.c"
+
 #ifdef IS_LITTLE_ENDIAN
 
 #define PREFIX(ident) little2_ ## ident
diff --git a/parser/expat/lib/sources.mozbuild b/parser/expat/lib/sources.mozbuild
index 30d0f76c0ab4..1a8212a080c2 100644
--- a/parser/expat/lib/sources.mozbuild
+++ b/parser/expat/lib/sources.mozbuild
@@ -5,7 +5,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 expat_sources = [
-    'xmlparse.c',
+    'moz_xmlparse.c',
     'xmlrole.c',
     'xmltok.c',
 ]
diff --git a/parser/expat/lib/xmlparse.c b/parser/expat/lib/xmlparse.c
index d4fba8b8580e..89ffd35e5163 100644
--- a/parser/expat/lib/xmlparse.c
+++ b/parser/expat/lib/xmlparse.c
@@ -2145,13 +2145,7 @@ XML_GetBuffer(XML_Parser parser, int len)
 }
 
 enum XML_Status XMLCALL
-/* BEGIN MOZILLA CHANGE (Bug 1743007 - Convert expat XML_StopParser API to take an int param instead of u8) */
-#if 0
 XML_StopParser(XML_Parser parser, XML_Bool resumable)
-#else
-XML_StopParser(XML_Parser parser, int resumable)
-#endif
-/* END MOZILLA CHANGE */
 {
   if (parser == NULL)
     return XML_STATUS_ERROR;
diff --git a/parser/expat/lib/xmltok.c b/parser/expat/lib/xmltok.c
index 76e94fe0fa51..5e52b59b8a6e 100644
--- a/parser/expat/lib/xmltok.c
+++ b/parser/expat/lib/xmltok.c
@@ -1758,11 +1758,3 @@ XmlInitUnknownEncodingNS(void *mem,
 }
 
 #endif /* XML_NS */
-
-/* BEGIN MOZILLA CHANGE (Mozilla extensions for QName checking) */
-#ifdef MOZILLA_CLIENT
-#ifndef MOZ_IN_WASM_SANDBOX
-#include "moz_extensions.c"
-#endif
-#endif /* MOZILLA_CLIENT */
-/* END MOZILLA CHANGE */
diff --git a/parser/htmlparser/nsExpatDriver.h b/parser/htmlparser/nsExpatDriver.h
index b07ba72b6b46..bd89711a0f82 100644
--- a/parser/htmlparser/nsExpatDriver.h
+++ b/parser/htmlparser/nsExpatDriver.h
@@ -7,7 +7,7 @@
 #define NS_EXPAT_DRIVER__
 
 #include "expat_config.h"
-#include "expat.h"
+#include "moz_expat.h"
 #include "nsCOMPtr.h"
 #include "nsString.h"
 #include "nsIDTD.h"