diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -733,6 +733,10 @@
 coreconfigitem('format', 'usestore',
     default=True,
 )
+coreconfigitem('format', 'exp-use-copies-side-data-changeset',
+    default=False,
+    experimental=True,
+)
 coreconfigitem('format', 'use-side-data',
     default=False,
     experimental=True,
diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -398,6 +398,10 @@
 # information for revision without altering their original hashes.
 SIDEDATA_REQUIREMENT = 'exp-sidedata-flag'
 
+# A repository with the the copies-sidedata-changeset requirement will store
+# copies related information in changeset's sidedata.
+COPIESSDC_REQUIREMENT = 'exp-copies-sidedata-changeset'
+
 # Functions receiving (ui, features) that extensions can register to impact
 # the ability to load repositories with custom requirements. Only
 # functions defined in loaded extensions are called.
@@ -923,6 +927,7 @@
         'revlogv1',
         'generaldelta',
         'treemanifest',
+        COPIESSDC_REQUIREMENT,
         REVLOGV2_REQUIREMENT,
         SIDEDATA_REQUIREMENT,
         SPARSEREVLOG_REQUIREMENT,
@@ -3165,6 +3170,10 @@
     # experimental config: format.use-side-data
     if ui.configbool('format', 'use-side-data'):
         requirements.add(SIDEDATA_REQUIREMENT)
+    # experimental config: format.exp-use-copies-side-data-changeset
+    if ui.configbool('format', 'exp-use-copies-side-data-changeset'):
+        requirements.add(SIDEDATA_REQUIREMENT)
+        requirements.add(COPIESSDC_REQUIREMENT)
     if ui.configbool('experimental', 'treemanifest'):
         requirements.add('treemanifest')