diff --git a/Makefile.am b/Makefile.am
index 3e55230ee..90b504b5c 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -192,13 +192,13 @@ CLEANFILES = $(VC6_LIBDSP) $(VC6_SRCDSP) $(VC7_LIBVCPROJ) $(VC7_SRCVCPROJ) \
  $(VC11_LIBVCXPROJ) $(VC11_SRCVCXPROJ) $(VC12_LIBVCXPROJ) $(VC12_SRCVCXPROJ) \
  $(VC14_LIBVCXPROJ) $(VC14_SRCVCXPROJ) $(VC15_LIBVCXPROJ) $(VC15_SRCVCXPROJ)
 
-bin_SCRIPTS = curl-config
+bin_SCRIPTS = curl-impersonate-ff-config
 
 SUBDIRS = lib src
 DIST_SUBDIRS = $(SUBDIRS) tests packages scripts include docs
 
 pkgconfigdir = $(libdir)/pkgconfig
-pkgconfig_DATA = libcurl.pc
+pkgconfig_DATA = libcurl-impersonate-ff.pc
 
 # List of files required to generate VC IDE .dsp, .vcproj and .vcxproj files
 include lib/Makefile.inc
diff --git a/configure.ac b/configure.ac
index 63e320236..238addfaa 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1331,7 +1331,8 @@ if test X"$OPT_BROTLI" != Xno; then
 
   dnl if given with a prefix, we set -L and -I based on that
   if test -n "$PREFIX_BROTLI"; then
-    LIB_BROTLI="-lbrotlidec"
+    # curl-impersonate: Use static libbrotli
+    LIB_BROTLI="-Wl,-Bstatic -lbrotlidec-static -lbrotlicommon-static -Wl,-Bdynamic"
     LD_BROTLI=-L${PREFIX_BROTLI}/lib$libsuff
     CPP_BROTLI=-I${PREFIX_BROTLI}/include
     DIR_BROTLI=${PREFIX_BROTLI}/lib$libsuff
@@ -1341,7 +1342,11 @@ if test X"$OPT_BROTLI" != Xno; then
   CPPFLAGS="$CPPFLAGS $CPP_BROTLI"
   LIBS="$LIB_BROTLI $LIBS"
 
-  AC_CHECK_LIB(brotlidec, BrotliDecoderDecompress)
+  AC_CHECK_LIB(brotlidec, BrotliDecoderDecompress,
+    # curl-impersonate: Define 'action-if-found' explicitly to prevent
+    # -lbrotlidec from being added to LIBS (already added before)
+    AC_DEFINE(HAVE_LIBBROTLI, 1, [Define to 1 if libbrotli exists])
+  )
 
   AC_CHECK_HEADERS(brotli/decode.h,
     curl_brotli_msg="enabled (libbrotlidec)"
@@ -2573,15 +2578,15 @@ if test X"$want_nghttp2" != Xno; then
 
   if test "$PKGCONFIG" != "no" ; then
     LIB_H2=`CURL_EXPORT_PCDIR([$want_nghttp2_path])
-      $PKGCONFIG --libs-only-l libnghttp2`
+      $PKGCONFIG --static --libs-only-l libnghttp2`
     AC_MSG_NOTICE([-l is $LIB_H2])
 
     CPP_H2=`CURL_EXPORT_PCDIR([$want_nghttp2_path]) dnl
-      $PKGCONFIG --cflags-only-I libnghttp2`
+      $PKGCONFIG --static --cflags-only-I libnghttp2`
     AC_MSG_NOTICE([-I is $CPP_H2])
 
     LD_H2=`CURL_EXPORT_PCDIR([$want_nghttp2_path])
-      $PKGCONFIG --libs-only-L libnghttp2`
+      $PKGCONFIG --static --libs-only-L libnghttp2`
     AC_MSG_NOTICE([-L is $LD_H2])
 
     LDFLAGS="$LDFLAGS $LD_H2"
@@ -4255,8 +4260,8 @@ AC_CONFIG_FILES([Makefile \
            tests/unit/Makefile \
            packages/Makefile \
            packages/vms/Makefile \
-           curl-config \
-           libcurl.pc
+           curl-impersonate-ff-config:curl-config.in \
+           libcurl-impersonate-ff.pc:libcurl.pc.in
 ])
 AC_OUTPUT
 
diff --git a/curl-config.in b/curl-config.in
index 8b4a29a9a..2c8b888d8 100644
--- a/curl-config.in
+++ b/curl-config.in
@@ -161,9 +161,9 @@ while test $# -gt 0; do
            CURLLIBDIR=""
         fi
         if test "X@ENABLE_SHARED@" = "Xno"; then
-          echo ${CURLLIBDIR}-lcurl @LIBCURL_LIBS@
+          echo ${CURLLIBDIR}-lcurl-impersonate-ff @LIBCURL_LIBS@
         else
-          echo ${CURLLIBDIR}-lcurl
+          echo ${CURLLIBDIR}-lcurl-impersonate-ff
         fi
         ;;
     --ssl-backends)
@@ -172,7 +172,7 @@ while test $# -gt 0; do
 
     --static-libs)
         if test "X@ENABLE_STATIC@" != "Xno" ; then
-          echo @libdir@/libcurl.@libext@ @LDFLAGS@ @LIBCURL_LIBS@
+          echo @libdir@/libcurl-impersonate-ff.@libext@ @LDFLAGS@ @LIBCURL_LIBS@
         else
           echo "curl was built with static libraries disabled" >&2
           exit 1
diff --git a/include/curl/curl.h b/include/curl/curl.h
index 7b69ce2d6..fe4bb36b9 100644
--- a/include/curl/curl.h
+++ b/include/curl/curl.h
@@ -2135,6 +2135,10 @@ typedef enum {
   /* Set MIME option flags. */
   CURLOPT(CURLOPT_MIME_OPTIONS, CURLOPTTYPE_LONG, 315),
 
+  /* curl-impersonate: A list of headers used by the impersonated browser.
+   * If given, merged with CURLOPT_HTTPHEADER. */
+  CURLOPT(CURLOPT_HTTPBASEHEADER, CURLOPTTYPE_SLISTPOINT, 316),
+
   CURLOPT_LASTENTRY /* the last unused */
 } CURLoption;
 
diff --git a/include/curl/easy.h b/include/curl/easy.h
index 2dbfb26b5..e0bf86169 100644
--- a/include/curl/easy.h
+++ b/include/curl/easy.h
@@ -41,6 +41,15 @@ CURL_EXTERN CURLcode curl_easy_setopt(CURL *curl, CURLoption option, ...);
 CURL_EXTERN CURLcode curl_easy_perform(CURL *curl);
 CURL_EXTERN void curl_easy_cleanup(CURL *curl);
 
+/*
+ * curl-impersonate: Tell libcurl to impersonate a browser.
+ * This is a wrapper function that calls curl_easy_setopt()
+ * multiple times with all the parameters required. That's also why it was
+ * created as a separate API function and not just as another option to
+ * curl_easy_setopt().
+ */
+CURL_EXTERN CURLcode curl_easy_impersonate(CURL *curl, const char *target);
+
 /*
  * NAME curl_easy_getinfo()
  *
diff --git a/lib/Makefile.am b/lib/Makefile.am
index 769363941..6e2f1b829 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -32,7 +32,7 @@ EXTRA_DIST = Makefile.m32 config-win32.h config-win32ce.h           \
  firefox-db2pem.sh config-vxworks.h Makefile.vxworks checksrc.pl    \
  setup-win32.h .checksrc
 
-lib_LTLIBRARIES = libcurl.la
+lib_LTLIBRARIES = libcurl-impersonate-ff.la
 
 if BUILD_UNITTESTS
 noinst_LTLIBRARIES = libcurlu.la
@@ -84,43 +84,43 @@ AM_CPPFLAGS += -DBUILDING_LIBCURL
 AM_LDFLAGS =
 AM_CFLAGS =
 
-libcurl_la_CPPFLAGS_EXTRA =
-libcurl_la_LDFLAGS_EXTRA =
-libcurl_la_CFLAGS_EXTRA =
+libcurl_impersonate_ff_la_CPPFLAGS_EXTRA =
+libcurl_impersonate_ff_la_LDFLAGS_EXTRA =
+libcurl_impersonate_ff_la_CFLAGS_EXTRA =
 
 if CURL_LT_SHLIB_USE_VERSION_INFO
-libcurl_la_LDFLAGS_EXTRA += $(VERSIONINFO)
+libcurl_impersonate_ff_la_LDFLAGS_EXTRA += $(VERSIONINFO)
 endif
 
 if CURL_LT_SHLIB_USE_NO_UNDEFINED
-libcurl_la_LDFLAGS_EXTRA += -no-undefined
+libcurl_impersonate_ff_la_LDFLAGS_EXTRA += -no-undefined
 endif
 
 if CURL_LT_SHLIB_USE_MIMPURE_TEXT
-libcurl_la_LDFLAGS_EXTRA += -mimpure-text
+libcurl_impersonate_ff_la_LDFLAGS_EXTRA += -mimpure-text
 endif
 
 if CURL_LT_SHLIB_USE_VERSIONED_SYMBOLS
-libcurl_la_LDFLAGS_EXTRA += -Wl,--version-script=libcurl.vers
+libcurl_impersonate_ff_la_LDFLAGS_EXTRA += -Wl,--version-script=libcurl.vers
 else
 # if symbol-hiding is enabled, hide them!
 if DOING_CURL_SYMBOL_HIDING
-libcurl_la_LDFLAGS_EXTRA += -export-symbols-regex '^curl_.*'
+libcurl_impersonate_ff_la_LDFLAGS_EXTRA += -export-symbols-regex '^curl_.*'
 endif
 endif
 
 if USE_CPPFLAG_CURL_STATICLIB
-libcurl_la_CPPFLAGS_EXTRA += -DCURL_STATICLIB
+libcurl_impersonate_ff_la_CPPFLAGS_EXTRA += -DCURL_STATICLIB
 endif
 
 if DOING_CURL_SYMBOL_HIDING
-libcurl_la_CPPFLAGS_EXTRA += -DCURL_HIDDEN_SYMBOLS
-libcurl_la_CFLAGS_EXTRA += $(CFLAG_CURL_SYMBOL_HIDING)
+libcurl_impersonate_ff_la_CPPFLAGS_EXTRA += -DCURL_HIDDEN_SYMBOLS
+libcurl_impersonate_ff_la_CFLAGS_EXTRA += $(CFLAG_CURL_SYMBOL_HIDING)
 endif
 
-libcurl_la_CPPFLAGS = $(AM_CPPFLAGS) $(libcurl_la_CPPFLAGS_EXTRA)
-libcurl_la_LDFLAGS = $(AM_LDFLAGS) $(libcurl_la_LDFLAGS_EXTRA) $(LDFLAGS) $(LIBCURL_LIBS)
-libcurl_la_CFLAGS = $(AM_CFLAGS) $(libcurl_la_CFLAGS_EXTRA)
+libcurl_impersonate_ff_la_CPPFLAGS = $(AM_CPPFLAGS) $(libcurl_impersonate_ff_la_CPPFLAGS_EXTRA)
+libcurl_impersonate_ff_la_LDFLAGS = $(AM_LDFLAGS) $(libcurl_impersonate_ff_la_LDFLAGS_EXTRA) $(LDFLAGS) $(LIBCURL_LIBS)
+libcurl_impersonate_ff_la_CFLAGS = $(AM_CFLAGS) $(libcurl_impersonate_ff_la_CFLAGS_EXTRA)
 
 libcurlu_la_CPPFLAGS = $(AM_CPPFLAGS) -DCURL_STATICLIB -DUNITTESTS
 libcurlu_la_LDFLAGS = $(AM_LDFLAGS) -static $(LIBCURL_LIBS)
@@ -129,7 +129,7 @@ libcurlu_la_CFLAGS = $(AM_CFLAGS)
 # Makefile.inc provides the CSOURCES and HHEADERS defines
 include Makefile.inc
 
-libcurl_la_SOURCES = $(CSOURCES) $(HHEADERS)
+libcurl_impersonate_ff_la_SOURCES = $(CSOURCES) $(HHEADERS)
 libcurlu_la_SOURCES = $(CSOURCES) $(HHEADERS)
 
 CHECKSRC = $(CS_$(V))
diff --git a/lib/easy.c b/lib/easy.c
index 20293a710..f08403bc0 100644
--- a/lib/easy.c
+++ b/lib/easy.c
@@ -80,6 +80,7 @@
 #include "dynbuf.h"
 #include "altsvc.h"
 #include "hsts.h"
+#include "strcase.h"
 
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
@@ -282,6 +283,202 @@ void curl_global_cleanup(void)
   init_flags  = 0;
 }
 
+/*
+ * curl-impersonate: Options to be set for each supported target browser.
+ * Note: this does not include the HTTP headers, which are handled separately
+ * in Curl_http().
+ */
+#define IMPERSONATE_MAX_HEADERS 32
+static const struct impersonate_opts {
+  const char *target;
+  int httpversion;
+  int ssl_version;
+  const char *ciphers;
+  const char *http_headers[IMPERSONATE_MAX_HEADERS];
+  /* Other TLS options will come here in the future once they are
+   * configurable through curl_easy_setopt() */
+} impersonations[] = {
+  {
+    .target = "ff91esr",
+    .httpversion = CURL_HTTP_VERSION_2_0,
+    .ssl_version = CURL_SSLVERSION_TLSv1_2 | CURL_SSLVERSION_MAX_DEFAULT,
+    .ciphers =
+      "aes_128_gcm_sha_256,"
+      "chacha20_poly1305_sha_256,"
+      "aes_256_gcm_sha_384,"
+      "ecdhe_ecdsa_aes_128_gcm_sha_256,"
+      "ecdhe_rsa_aes_128_gcm_sha_256,"
+      "ecdhe_ecdsa_chacha20_poly1305_sha_256,"
+      "ecdhe_rsa_chacha20_poly1305_sha_256,"
+      "ecdhe_ecdsa_aes_256_gcm_sha_384,"
+      "ecdhe_rsa_aes_256_gcm_sha_384,"
+      "ecdhe_ecdsa_aes_256_sha,"
+      "ecdhe_ecdsa_aes_128_sha,"
+      "ecdhe_rsa_aes_128_sha,"
+      "ecdhe_rsa_aes_256_sha,"
+      "rsa_aes_128_gcm_sha_256,"
+      "rsa_aes_256_gcm_sha_384,"
+      "rsa_aes_128_sha,"
+      "rsa_aes_256_sha,"
+      "rsa_3des_ede_cbc_sha",
+    .http_headers = {
+      "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Firefox/91.0",
+      "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
+      "Accept-Language: en-US,en;q=0.5",
+      "Accept-Encoding: gzip, deflate, br",
+      "Upgrade-Insecure-Requests: 1",
+      "Sec-Fetch-Dest: document",
+      "Sec-Fetch-Mode: navigate",
+      "Sec-Fetch-Site: none",
+      "Sec-Fetch-User: ?1",
+      "TE: Trailers"
+    }
+  },
+  {
+    .target = "ff95",
+    .httpversion = CURL_HTTP_VERSION_2_0,
+    .ssl_version = CURL_SSLVERSION_TLSv1_2 | CURL_SSLVERSION_MAX_DEFAULT,
+    .ciphers =
+      "aes_128_gcm_sha_256,"
+      "chacha20_poly1305_sha_256,"
+      "aes_256_gcm_sha_384,"
+      "ecdhe_ecdsa_aes_128_gcm_sha_256,"
+      "ecdhe_rsa_aes_128_gcm_sha_256,"
+      "ecdhe_ecdsa_chacha20_poly1305_sha_256,"
+      "ecdhe_rsa_chacha20_poly1305_sha_256,"
+      "ecdhe_ecdsa_aes_256_gcm_sha_384,"
+      "ecdhe_rsa_aes_256_gcm_sha_384,"
+      "ecdhe_ecdsa_aes_256_sha,"
+      "ecdhe_ecdsa_aes_128_sha,"
+      "ecdhe_rsa_aes_128_sha,"
+      "ecdhe_rsa_aes_256_sha,"
+      "rsa_aes_128_gcm_sha_256,"
+      "rsa_aes_256_gcm_sha_384,"
+      "rsa_aes_128_sha,"
+      "rsa_aes_256_sha",
+    .http_headers = {
+      "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:95.0) Gecko/20100101 Firefox/95.0",
+      "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8",
+      "Accept-Language: en-US,en;q=0.5",
+      "Accept-Encoding: gzip, deflate, br",
+      "Upgrade-Insecure-Requests: 1",
+      "Sec-Fetch-Dest: document",
+      "Sec-Fetch-Mode: navigate",
+      "Sec-Fetch-Site: none",
+      "Sec-Fetch-User: ?1",
+      "TE: Trailers"
+    }
+  },
+  {
+    .target = "ff98",
+    .httpversion = CURL_HTTP_VERSION_2_0,
+    .ssl_version = CURL_SSLVERSION_TLSv1_2 | CURL_SSLVERSION_MAX_DEFAULT,
+    .ciphers =
+      "aes_128_gcm_sha_256,"
+      "chacha20_poly1305_sha_256,"
+      "aes_256_gcm_sha_384,"
+      "ecdhe_ecdsa_aes_128_gcm_sha_256,"
+      "ecdhe_rsa_aes_128_gcm_sha_256,"
+      "ecdhe_ecdsa_chacha20_poly1305_sha_256,"
+      "ecdhe_rsa_chacha20_poly1305_sha_256,"
+      "ecdhe_ecdsa_aes_256_gcm_sha_384,"
+      "ecdhe_rsa_aes_256_gcm_sha_384,"
+      "ecdhe_ecdsa_aes_256_sha,"
+      "ecdhe_ecdsa_aes_128_sha,"
+      "ecdhe_rsa_aes_128_sha,"
+      "ecdhe_rsa_aes_256_sha,"
+      "rsa_aes_128_gcm_sha_256,"
+      "rsa_aes_256_gcm_sha_384,"
+      "rsa_aes_128_sha,"
+      "rsa_aes_256_sha",
+    .http_headers = {
+      "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:98.0) Gecko/20100101 Firefox/98.0",
+      "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8",
+      "Accept-Language: en-US,en;q=0.5",
+      "Accept-Encoding: gzip, deflate, br",
+      "Upgrade-Insecure-Requests: 1",
+      "Sec-Fetch-Dest: document",
+      "Sec-Fetch-Mode: navigate",
+      "Sec-Fetch-Site: none",
+      "Sec-Fetch-User: ?1",
+      "TE: Trailers"
+    }
+  }
+};
+
+#define NUM_IMPERSONATIONS \
+  sizeof(impersonations) / sizeof(impersonations[0])
+
+/*
+ * curl-impersonate:
+ * Call curl_easy_setopt() with all the needed options as defined in the
+ * 'impersonations' array.
+ * */
+CURLcode curl_easy_impersonate(struct Curl_easy *data, const char *target)
+{
+  int i;
+  int ret;
+  const struct impersonate_opts *opts = NULL;
+  struct curl_slist *headers = NULL;
+
+  for(i = 0; i < NUM_IMPERSONATIONS; i++) {
+    if (Curl_strncasecompare(target,
+                             impersonations[i].target,
+                             strlen(impersonations[i].target))) {
+      opts = &impersonations[i];
+      break;
+    }
+  }
+
+  if(!opts) {
+    DEBUGF(fprintf(stderr, "Error: unknown impersonation target '%s'\n",
+                   target));
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+  }
+
+  if(opts->httpversion != CURL_HTTP_VERSION_NONE) {
+    ret = curl_easy_setopt(data, CURLOPT_HTTP_VERSION, opts->httpversion);
+    if(ret)
+      return ret;
+  }
+
+  if (opts->ssl_version != CURL_SSLVERSION_DEFAULT) {
+    ret = curl_easy_setopt(data, CURLOPT_SSLVERSION, opts->ssl_version);
+    if(ret)
+      return ret;
+  }
+
+  if(opts->ciphers) {
+    ret = curl_easy_setopt(data, CURLOPT_SSL_CIPHER_LIST, opts->ciphers);
+    if (ret)
+      return ret;
+  }
+
+  /* Build a linked list out of the static array of headers. */
+  for(i = 0; i < IMPERSONATE_MAX_HEADERS; i++) {
+    if(opts->http_headers[i]) {
+      headers = curl_slist_append(headers, opts->http_headers[i]);
+      if(!headers) {
+        return CURLE_OUT_OF_MEMORY;
+      }
+    }
+  }
+
+  if(headers) {
+    ret = curl_easy_setopt(data, CURLOPT_HTTPBASEHEADER, headers);
+    curl_slist_free_all(headers);
+    if(ret)
+      return ret;
+  }
+
+  /* Always enable all supported compressions. */
+  ret = curl_easy_setopt(data, CURLOPT_ACCEPT_ENCODING, "");
+  if(ret)
+    return ret;
+
+  return CURLE_OK;
+}
+
 /*
  * curl_easy_init() is the external interface to alloc, setup and init an
  * easy handle that is returned. If anything goes wrong, NULL is returned.
@@ -290,6 +487,7 @@ struct Curl_easy *curl_easy_init(void)
 {
   CURLcode result;
   struct Curl_easy *data;
+  char *target;
 
   /* Make sure we inited the global SSL stuff */
   if(!initialized) {
@@ -308,6 +506,22 @@ struct Curl_easy *curl_easy_init(void)
     return NULL;
   }
 
+  /*
+   * curl-impersonate: Hook into curl_easy_init() to set the required options
+   * from an environment variable.
+   * This is a bit hacky but allows seamless integration of libcurl-impersonate
+   * without code modifications to the app.
+   */
+  target = curl_getenv("CURL_IMPERSONATE");
+  if(target) {
+    result = curl_easy_impersonate(data, target);
+    free(target);
+    if(result) {
+      Curl_close(&data);
+      return NULL;
+    }
+  }
+
   return data;
 }
 
@@ -878,6 +1092,13 @@ struct Curl_easy *curl_easy_duphandle(struct Curl_easy *data)
     outcurl->state.referer_alloc = TRUE;
   }
 
+  if(data->state.base_headers) {
+    outcurl->state.base_headers =
+      Curl_slist_duplicate(data->state.base_headers);
+    if(!outcurl->state.base_headers)
+      goto fail;
+  }
+
   /* Reinitialize an SSL engine for the new handle
    * note: the engine name has already been copied by dupset */
   if(outcurl->set.str[STRING_SSL_ENGINE]) {
diff --git a/lib/easyoptions.c b/lib/easyoptions.c
index 04871ad1e..cd5998146 100644
--- a/lib/easyoptions.c
+++ b/lib/easyoptions.c
@@ -130,6 +130,7 @@ struct curl_easyoption Curl_easyopts[] = {
   {"HTTP200ALIASES", CURLOPT_HTTP200ALIASES, CURLOT_SLIST, 0},
   {"HTTPAUTH", CURLOPT_HTTPAUTH, CURLOT_VALUES, 0},
   {"HTTPGET", CURLOPT_HTTPGET, CURLOT_LONG, 0},
+  {"HTTPBASEHEADER", CURLOPT_HTTPBASEHEADER, CURLOT_SLIST, 0},
   {"HTTPHEADER", CURLOPT_HTTPHEADER, CURLOT_SLIST, 0},
   {"HTTPPOST", CURLOPT_HTTPPOST, CURLOT_OBJECT, 0},
   {"HTTPPROXYTUNNEL", CURLOPT_HTTPPROXYTUNNEL, CURLOT_LONG, 0},
diff --git a/lib/http.c b/lib/http.c
index f08a343e3..879151dd2 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -84,6 +84,7 @@
 #include "altsvc.h"
 #include "hsts.h"
 #include "c-hyper.h"
+#include "slist.h"
 
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
@@ -1795,6 +1796,15 @@ CURLcode Curl_add_custom_headers(struct Curl_easy *data,
   int numlists = 1; /* by default */
   int i;
 
+  /*
+   * curl-impersonate: Use the merged list of headers if it exists (i.e. when
+   * the CURLOPT_HTTPBASEHEADER option was set.
+   */
+  struct curl_slist *noproxyheaders =
+    (data->state.merged_headers ?
+     data->state.merged_headers :
+     data->set.headers);
+
 #ifndef CURL_DISABLE_PROXY
   enum proxy_use proxy;
 
@@ -1806,10 +1816,10 @@ CURLcode Curl_add_custom_headers(struct Curl_easy *data,
 
   switch(proxy) {
   case HEADER_SERVER:
-    h[0] = data->set.headers;
+    h[0] = noproxyheaders;
     break;
   case HEADER_PROXY:
-    h[0] = data->set.headers;
+    h[0] = noproxyheaders;
     if(data->set.sep_headers) {
       h[1] = data->set.proxyheaders;
       numlists++;
@@ -1819,12 +1829,12 @@ CURLcode Curl_add_custom_headers(struct Curl_easy *data,
     if(data->set.sep_headers)
       h[0] = data->set.proxyheaders;
     else
-      h[0] = data->set.headers;
+      h[0] = noproxyheaders;
     break;
   }
 #else
   (void)is_connect;
-  h[0] = data->set.headers;
+  h[0] = noproxyheaders;
 #endif
 
   /* loop through one or two lists */
@@ -2059,6 +2069,92 @@ void Curl_http_method(struct Curl_easy *data, struct connectdata *conn,
   *reqp = httpreq;
 }
 
+/*
+ * curl-impersonate:
+ * Create a new linked list of headers.
+ * The new list is a merge between the "base" headers and the application given
+ * headers. The "base" headers contain curl-impersonate's list of headers
+ * used by default by the impersonated browser.
+ *
+ * The application given headers will override the "base" headers if supplied.
+ */
+CURLcode Curl_http_merge_headers(struct Curl_easy *data)
+{
+  int i;
+  int ret;
+  struct curl_slist *head;
+  struct curl_slist *dup = NULL;
+  struct curl_slist *new_list = NULL;
+
+  if (!data->state.base_headers)
+    return CURLE_OK;
+
+  /* Duplicate the list for temporary use. */
+  if (data->set.headers) {
+    dup = Curl_slist_duplicate(data->set.headers);
+    if(!dup)
+      return CURLE_OUT_OF_MEMORY;
+  }
+
+  for(head = data->state.base_headers; head; head = head->next) {
+    char *sep;
+    size_t prefix_len;
+    bool found = FALSE;
+    struct curl_slist *head2;
+
+    sep = strchr(head->data, ':');
+    if(!sep)
+      continue;
+
+    prefix_len = sep - head->data;
+
+    /* Check if this header was added by the application. */
+    for(head2 = dup; head2; head2 = head2->next) {
+      if(head2->data &&
+         strncasecompare(head2->data, head->data, prefix_len) &&
+         Curl_headersep(head2->data[prefix_len]) ) {
+        new_list = curl_slist_append(new_list, head2->data);
+        /* Free and set to NULL to mark that it's been added. */
+        Curl_safefree(head2->data);
+        found = TRUE;
+        break;
+      }
+    }
+
+    if (!found) {
+      new_list = curl_slist_append(new_list, head->data);
+    }
+
+    if (!new_list) {
+      ret = CURLE_OUT_OF_MEMORY;
+      goto fail;
+    }
+  }
+
+  /* Now go over any additional application-supplied headers. */
+  for(head = dup; head; head = head->next) {
+    if(head->data) {
+      new_list = curl_slist_append(new_list, head->data);
+      if(!new_list) {
+        ret = CURLE_OUT_OF_MEMORY;
+        goto fail;
+      }
+    }
+  }
+
+  curl_slist_free_all(dup);
+  /* Save the new, merged list separately, so it can be freed later. */
+  curl_slist_free_all(data->state.merged_headers);
+  data->state.merged_headers = new_list;
+
+  return CURLE_OK;
+
+fail:
+  Curl_safefree(dup);
+  curl_slist_free_all(new_list);
+  return ret;
+}
+
 CURLcode Curl_http_useragent(struct Curl_easy *data)
 {
   /* The User-Agent string might have been allocated in url.c already, because
@@ -3067,6 +3163,11 @@ CURLcode Curl_http(struct Curl_easy *data, bool *done)
   if(result)
     return result;
 
+  /* curl-impersonate: Add HTTP headers to impersonate real browsers. */
+  result = Curl_http_merge_headers(data);
+  if (result)
+    return result;
+
   result = Curl_http_useragent(data);
   if(result)
     return result;
diff --git a/lib/http2.c b/lib/http2.c
index e74400a4c..1f4d496f3 100644
--- a/lib/http2.c
+++ b/lib/http2.c
@@ -1818,7 +1818,8 @@ static ssize_t http2_recv(struct Curl_easy *data, int sockindex,
 
 /* Index where :authority header field will appear in request header
    field list. */
-#define AUTHORITY_DST_IDX 3
+/* curl-impersonate: Put the ":authority" header in the second place. */
+#define AUTHORITY_DST_IDX 2
 
 /* USHRT_MAX is 65535 == 0xffff */
 #define HEADER_OVERFLOW(x) \
diff --git a/lib/setopt.c b/lib/setopt.c
index 599ed5d99..1baa48e70 100644
--- a/lib/setopt.c
+++ b/lib/setopt.c
@@ -48,6 +48,7 @@
 #include "multiif.h"
 #include "altsvc.h"
 #include "hsts.h"
+#include "slist.h"
 
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
@@ -688,6 +689,23 @@ CURLcode Curl_vsetopt(struct Curl_easy *data, CURLoption option, va_list param)
                             va_arg(param, char *));
     break;
 
+  case CURLOPT_HTTPBASEHEADER:
+    /*
+     * curl-impersonate:
+     * Set a list of "base" headers. These will be merged with any headers
+     * set by CURLOPT_HTTPHEADER. curl-impersonate uses this option in order
+     * to set a list of default browser headers.
+     *
+     * Unlike CURLOPT_HTTPHEADER,
+     * the list is copied and can be immediately freed by the user.
+     */
+    curl_slist_free_all(data->state.base_headers);
+    data->state.base_headers = \
+      Curl_slist_duplicate(va_arg(param, struct curl_slist *));
+    if (!data->state.base_headers)
+      result = CURLE_OUT_OF_MEMORY;
+    break;
+
   case CURLOPT_HTTPHEADER:
     /*
      * Set a list with HTTP headers to use (or replace internals with)
diff --git a/lib/transfer.c b/lib/transfer.c
index 22704fa15..1e100140c 100644
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -102,7 +102,15 @@ char *Curl_checkheaders(const struct Curl_easy *data,
   DEBUGASSERT(thislen);
   DEBUGASSERT(thisheader[thislen-1] != ':');
 
-  for(head = data->set.headers; head; head = head->next) {
+  /*
+   * curl-impersonate:
+   * Check if we have overriden the user-supplied list of headers.
+   */
+  head = data->set.headers;
+  if (data->state.merged_headers)
+    head = data->state.merged_headers;
+
+  for(; head; head = head->next) {
     if(strncasecompare(head->data, thisheader, thislen) &&
        Curl_headersep(head->data[thislen]) )
       return head->data;
diff --git a/lib/url.c b/lib/url.c
index 9f1013554..f0f266797 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -469,6 +469,11 @@ CURLcode Curl_close(struct Curl_easy **datap)
   Curl_safefree(data->state.aptr.proxyuser);
   Curl_safefree(data->state.aptr.proxypasswd);
 
+  /* curl-impersonate: Free the list set by CURLOPT_HTTPBASEHEADER. */
+  curl_slist_free_all(data->state.base_headers);
+  /* curl-impersonate: Free the dynamic list of headers. */
+  curl_slist_free_all(data->state.merged_headers);
+
 #ifndef CURL_DISABLE_DOH
   if(data->req.doh) {
     Curl_dyn_free(&data->req.doh->probe[0].serverdoh);
diff --git a/lib/urldata.h b/lib/urldata.h
index cc9c88870..a35a20e10 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -1421,6 +1421,19 @@ struct UrlState {
   CURLcode hresult; /* used to pass return codes back from hyper callbacks */
 #endif
 
+  /*
+   * curl-impersonate:
+   * List of "base" headers set by CURLOPT_HTTPBASEHEADER.
+   */
+  struct curl_slist *base_headers;
+  /*
+   * curl-impersonate:
+   * Dynamically-constructed list of HTTP headers.
+   * This list is a merge of the default HTTP headers needed to impersonate a
+   * browser, together with any user-supplied headers.
+   */
+  struct curl_slist *merged_headers;
+
   /* Dynamically allocated strings, MUST be freed before this struct is
      killed. */
   struct dynamically_allocated_data {
diff --git a/lib/vtls/nss.c b/lib/vtls/nss.c
index 2b44f0512..4c60797c7 100644
--- a/lib/vtls/nss.c
+++ b/lib/vtls/nss.c
@@ -143,6 +143,7 @@ static const struct cipher_s cipherlist[] = {
   {"dhe_dss_3des_sha",           SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA},
   {"dhe_rsa_des_sha",            SSL_DHE_RSA_WITH_DES_CBC_SHA},
   {"dhe_dss_des_sha",            SSL_DHE_DSS_WITH_DES_CBC_SHA},
+  {"rsa_3des_ede_cbc_sha",       TLS_RSA_WITH_3DES_EDE_CBC_SHA},
   /* TLS 1.0: Exportable 56-bit Cipher Suites. */
   {"rsa_des_56_sha",             TLS_RSA_EXPORT1024_WITH_DES_CBC_SHA},
   {"rsa_rc4_56_sha",             TLS_RSA_EXPORT1024_WITH_RC4_56_SHA},
@@ -378,6 +379,95 @@ static SECStatus set_ciphers(struct Curl_easy *data, PRFileDesc *model,
   return SECSuccess;
 }
 
+/* See nsSSLIOLayerSetOptions@nsNSSIOLayer.cpp, Firefox source code */
+const SSLNamedGroup named_groups[] = {
+  ssl_grp_ec_curve25519, ssl_grp_ec_secp256r1, ssl_grp_ec_secp384r1,
+  ssl_grp_ec_secp521r1,  ssl_grp_ffdhe_2048,   ssl_grp_ffdhe_3072};
+
+#define NUM_OF_NAMED_GROUPS sizeof(named_groups)/sizeof(named_groups[0])
+
+static SECStatus set_named_groups(PRFileDesc *model)
+{
+  /* This aligns TLS extension 10 (supported_groups) to what Firefox does. */
+  return SSL_NamedGroupConfig(model, named_groups, NUM_OF_NAMED_GROUPS);
+}
+
+static const SSLSignatureScheme signatures[] = {
+    ssl_sig_ecdsa_secp256r1_sha256, ssl_sig_ecdsa_secp384r1_sha384,
+    ssl_sig_ecdsa_secp521r1_sha512, ssl_sig_rsa_pss_sha256,
+    ssl_sig_rsa_pss_sha384,         ssl_sig_rsa_pss_sha512,
+    ssl_sig_rsa_pkcs1_sha256,       ssl_sig_rsa_pkcs1_sha384,
+    ssl_sig_rsa_pkcs1_sha512,       ssl_sig_ecdsa_sha1,
+    ssl_sig_rsa_pkcs1_sha1
+};
+
+#define NUM_OF_SIGNATURES sizeof(signatures)/sizeof(signatures[0])
+
+static SECStatus set_additional_key_shares(PRFileDesc *model)
+{
+  /* This aligns TLS extension 51 (key_share) to what Firefox does. */
+  return SSL_SendAdditionalKeyShares(model, 1);
+}
+
+static SECStatus set_signatures(PRFileDesc *model)
+{
+  /* Align TLS extension 13 (signature_algorithms) to what Firefox does. */
+  return SSL_SignatureSchemePrefSet(model, signatures, NUM_OF_SIGNATURES);
+}
+
+static SECStatus set_ssl_options(PRFileDesc *model)
+{
+  SECStatus s;
+
+  /* Enable TLS 1.3 compat mode. Firefox does this, as can be seen at
+   * nsSSLIOLayerSetOptions()@nsNSSIOLayer.cpp.
+   * This has the side effect of NSS faking a TLS session ID.
+   * See ssl3_CreateClientHelloPreamble()@ssl3con.c
+   */
+  s = SSL_OptionSet(model, SSL_ENABLE_TLS13_COMPAT_MODE, PR_TRUE);
+  if (s != SECSuccess) {
+      return s;
+  }
+
+  /* Firefox sets the following options. I don't know what they do. */
+  s = SSL_OptionSet(model, SSL_REQUIRE_SAFE_NEGOTIATION, false);
+  if (s != SECSuccess) {
+      return s;
+  }
+  s = SSL_OptionSet(model, SSL_ENABLE_EXTENDED_MASTER_SECRET, true);
+  if (s != SECSuccess) {
+      return s;
+  }
+  s = SSL_OptionSet(model, SSL_ENABLE_HELLO_DOWNGRADE_CHECK, true);
+  if (s != SECSuccess) {
+      return s;
+  }
+  s = SSL_OptionSet(model, SSL_ENABLE_0RTT_DATA, true);
+  if (s != SECSuccess) {
+      return s;
+  }
+
+  /* This adds TLS extension 34 to the Client Hello. */
+  s = SSL_OptionSet(model, SSL_ENABLE_DELEGATED_CREDENTIALS, true);
+  if (s != SECSuccess) {
+      return s;
+  }
+
+  /* This adds TLS extension 5 (status_request) to the Client Hello. */
+  s = SSL_OptionSet(model, SSL_ENABLE_OCSP_STAPLING, true);
+  if (s != SECSuccess) {
+      return s;
+  }
+
+  /* Remove TLS extension 18 (signed_certificate_timestamp) */
+  s = SSL_OptionSet(model, SSL_ENABLE_SIGNED_CERT_TIMESTAMPS, false);
+  if (s != SECSuccess) {
+      return s;
+  }
+
+  return SSL_OptionSet(model, SSL_HANDSHAKE_AS_CLIENT, true);
+}
+
 /*
  * Return true if at least one cipher-suite is enabled. Used to determine
  * if we need to call NSS_SetDomesticPolicy() to enable the default ciphers.
@@ -1320,6 +1410,24 @@ static CURLcode nss_load_module(SECMODModule **pmod, const char *library,
 
   if(module)
     SECMOD_DestroyModule(module);
+
+  /* Patch for Ubuntu - add a "nss/" suffix to the library name */
+  config_string = aprintf("library=/usr/lib/x86_64-linux-gnu/nss/%s name=%s", library, name);
+  if(!config_string)
+    return CURLE_OUT_OF_MEMORY;
+
+  module = SECMOD_LoadUserModule(config_string, NULL, PR_FALSE);
+  free(config_string);
+
+  if(module && module->loaded) {
+    /* loaded successfully */
+    *pmod = module;
+    return CURLE_OK;
+  }
+
+  if(module)
+    SECMOD_DestroyModule(module);
+
   return CURLE_FAILED_INIT;
 }
 
@@ -1921,6 +2029,12 @@ static CURLcode nss_setup_connect(struct Curl_easy *data,
   if(SSL_OptionSet(model, SSL_NO_CACHE, ssl_no_cache) != SECSuccess)
     goto error;
 
+  if(SSL_SET_OPTION(primary.sessionid)) {
+    if(SSL_OptionSet(model, SSL_ENABLE_SESSION_TICKETS,
+                     PR_TRUE) != SECSuccess)
+      goto error;
+  }
+
   /* enable/disable the requested SSL version(s) */
   if(nss_init_sslver(&sslver, data, conn) != CURLE_OK)
     goto error;
@@ -1960,6 +2074,14 @@ static CURLcode nss_setup_connect(struct Curl_easy *data,
     }
   }
 
+  if (set_named_groups(model) != SECSuccess ||
+      set_additional_key_shares(model) != SECSuccess ||
+      set_signatures(model) != SECSuccess ||
+      set_ssl_options(model) != SECSuccess) {
+      result = CURLE_SSL_CIPHER;
+      goto error;
+  }
+
   if(!SSL_CONN_CONFIG(verifypeer) && SSL_CONN_CONFIG(verifyhost))
     infof(data, "warning: ignoring value of ssl.verifyhost");
 
@@ -2113,6 +2235,10 @@ static CURLcode nss_setup_connect(struct Curl_easy *data,
     int cur = 0;
     unsigned char protocols[128];
 
+    protocols[cur++] = ALPN_HTTP_1_1_LENGTH;
+    memcpy(&protocols[cur], ALPN_HTTP_1_1, ALPN_HTTP_1_1_LENGTH);
+    cur += ALPN_HTTP_1_1_LENGTH;
+
 #ifdef USE_HTTP2
     if(data->state.httpwant >= CURL_HTTP_VERSION_2
 #ifndef CURL_DISABLE_PROXY
@@ -2124,9 +2250,6 @@ static CURLcode nss_setup_connect(struct Curl_easy *data,
       cur += ALPN_H2_LENGTH;
     }
 #endif
-    protocols[cur++] = ALPN_HTTP_1_1_LENGTH;
-    memcpy(&protocols[cur], ALPN_HTTP_1_1, ALPN_HTTP_1_1_LENGTH);
-    cur += ALPN_HTTP_1_1_LENGTH;
 
     if(SSL_SetNextProtoNego(backend->handle, protocols, cur) != SECSuccess)
       goto error;
diff --git a/libcurl.pc.in b/libcurl.pc.in
index 8ac15d407..68d01b219 100644
--- a/libcurl.pc.in
+++ b/libcurl.pc.in
@@ -34,6 +34,6 @@ Name: libcurl
 URL: https://curl.se/
 Description: Library to transfer files with ftp, http, etc.
 Version: @CURLVERSION@
-Libs: -L${libdir} -lcurl @LIBCURL_NO_SHARED@
+Libs: -L${libdir} -lcurl-impersonate-ff @LIBCURL_NO_SHARED@
 Libs.private: @LIBCURL_LIBS@
 Cflags: -I${includedir} @CPPFLAG_CURL_STATICLIB@
diff --git a/m4/curl-nss.m4 b/m4/curl-nss.m4
index 397ba71b1..abc09a91c 100644
--- a/m4/curl-nss.m4
+++ b/m4/curl-nss.m4
@@ -74,7 +74,7 @@ if test "x$OPT_NSS" != xno; then
       # Without pkg-config, we'll kludge in some defaults
       AC_MSG_WARN([Using hard-wired libraries and compilation flags for NSS.])
       addld="-L$OPT_NSS/lib"
-      addlib="-lssl3 -lsmime3 -lnss3 -lplds4 -lplc4 -lnspr4"
+      addlib="-Wl,-Bstatic -Wl,--start-group -lssl -lnss_static -lpk11wrap_static -lcertdb -lcerthi -lsmime -lnsspki -lnssdev -lsoftokn_static -lfreebl_static -lsha-x86_c_lib -lgcm-aes-x86_c_lib -lhw-acc-crypto-avx -lhw-acc-crypto-avx2  -lnssutil -lnssb -lcryptohi -l:libplc4.a -l:libplds4.a -l:libnspr4.a -lsqlite -Wl,--end-group -Wl,-Bdynamic -pthread -ldl"
       addcflags="-I$OPT_NSS/include"
       version="unknown"
       nssprefix=$OPT_NSS
@@ -91,7 +91,7 @@ if test "x$OPT_NSS" != xno; then
     fi
 
     dnl The function SSL_VersionRangeSet() is needed to enable TLS > 1.0
-    AC_CHECK_LIB(nss3, SSL_VersionRangeSet,
+    AC_CHECK_LIB(nss_static, SSL_VersionRangeSet,
      [
      AC_DEFINE(USE_NSS, 1, [if NSS is enabled])
      AC_SUBST(USE_NSS, [1])
diff --git a/src/Makefile.am b/src/Makefile.am
index c8abc93b1..fcecb10d0 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -41,7 +41,7 @@ AM_CPPFLAGS = -I$(top_srcdir)/include        \
               -I$(top_srcdir)/lib            \
               -I$(top_srcdir)/src
 
-bin_PROGRAMS = curl
+bin_PROGRAMS = curl-impersonate-ff
 
 SUBDIRS = ../docs
 
@@ -52,7 +52,7 @@ endif
 include Makefile.inc
 
 # CURL_FILES comes from Makefile.inc
-curl_SOURCES = $(CURL_FILES)
+curl_impersonate_ff_SOURCES = $(CURL_FILES)
 
 # This might hold -Werror
 CFLAGS += @CURL_CFLAG_EXTRAS@
@@ -61,9 +61,9 @@ CFLAGS += @CURL_CFLAG_EXTRAS@
 LIBS = $(BLANK_AT_MAKETIME)
 
 if USE_EXPLICIT_LIB_DEPS
-curl_LDADD = $(top_builddir)/lib/libcurl.la @LIBCURL_LIBS@
+curl_impersonate_ff_LDADD = $(top_builddir)/lib/libcurl-impersonate-ff.la @LIBCURL_LIBS@
 else
-curl_LDADD = $(top_builddir)/lib/libcurl.la @NSS_LIBS@ @SSL_LIBS@ @ZLIB_LIBS@ @CURL_NETWORK_AND_TIME_LIBS@
+curl_impersonate_ff_LDADD = $(top_builddir)/lib/libcurl-impersonate-ff.la @NSS_LIBS@ @SSL_LIBS@ @ZLIB_LIBS@ @CURL_NETWORK_AND_TIME_LIBS@
 endif
 
 # if unit tests are enabled, build a static library to link them with