diff --git a/swh/web/client/client.py b/swh/web/client/client.py
--- a/swh/web/client/client.py
+++ b/swh/web/client/client.py
@@ -189,6 +189,9 @@
         if http_method == "get":
             r = requests.get(url, **req_args, headers=headers)
             r.raise_for_status()
+        elif http_method == "post":
+            r = requests.post(url, **req_args, headers=headers)
+            r.raise_for_status()
         elif http_method == "head":
             r = requests.head(url, **req_args, headers=headers)
         else:
@@ -399,6 +402,28 @@
             else:
                 done = True
 
+    def known(
+        self, swhids: Iterator[SWHIDish], **req_args
+    ) -> Dict[SWHID, Dict[Any, Any]]:
+        """Verify the presence in the archive of several objects at once
+
+        Args:
+            swhids: SWHIDs of the objects to verify
+
+        Returns:
+            a dictionary mapping object SWHIDs to archive information about them; the
+            dictionary includes a "known" key associated to a boolean value that is true
+            if and only if the object is known to the archive
+
+        Raises:
+            requests.HTTPError: if HTTP request fails
+
+        """
+        r = self._call(
+            "known/", http_method="post", json=list(map(str, swhids)), **req_args
+        )
+        return {parse_swhid(k): v for k, v in r.json().items()}
+
     def content_exists(self, swhid: SWHIDish, **req_args) -> bool:
         """Check if a content object exists in the archive
 
diff --git a/swh/web/client/tests/conftest.py b/swh/web/client/tests/conftest.py
--- a/swh/web/client/tests/conftest.py
+++ b/swh/web/client/tests/conftest.py
@@ -29,6 +29,19 @@
                 "Link": f'<{API_URL}/origin/https://github.com/NixOS/nixpkgs/visits/?last_visit=40&per_page=10>; rel="next"'  # NoQA: E501
             }
         requests_mock.get(f"{API_URL}/{api_call}", text=data, headers=headers)
+
+    def known_callback(request, context):
+        known_swhids = [
+            "swh:1:cnt:fe95a46679d128ff167b7c55df5d02356c5a1ae1",
+            "swh:1:dir:977fc4b98c0e85816348cebd3b12026407c368b6",
+            "swh:1:rev:aafb16d69fd30ff58afdd69036a26047f3aebdc6",
+            "swh:1:rel:208f61cc7a5dbc9879ae6e5c2f95891e270f09ef",
+            "swh:1:snp:6a3a2cf0b2b90ce7ae1cf0a221ed68035b686f5a",
+        ]
+        return {swhid: {"known": swhid in known_swhids} for swhid in request.json()}
+
+    requests_mock.register_uri("POST", f"{API_URL}/known/", json=known_callback)
+
     return requests_mock
 
 
diff --git a/swh/web/client/tests/test_web_api_client.py b/swh/web/client/tests/test_web_api_client.py
--- a/swh/web/client/tests/test_web_api_client.py
+++ b/swh/web/client/tests/test_web_api_client.py
@@ -150,6 +150,25 @@
     assert visits[7]["snapshot"] == parse_swhid(snapshot_swhid)
 
 
+def test_known(web_api_client, web_api_mock):
+    # full list of SWHIDs for which we mock a {known: True} answer
+    known_swhids = [
+        "swh:1:cnt:fe95a46679d128ff167b7c55df5d02356c5a1ae1",
+        "swh:1:dir:977fc4b98c0e85816348cebd3b12026407c368b6",
+        "swh:1:rev:aafb16d69fd30ff58afdd69036a26047f3aebdc6",
+        "swh:1:rel:208f61cc7a5dbc9879ae6e5c2f95891e270f09ef",
+        "swh:1:snp:6a3a2cf0b2b90ce7ae1cf0a221ed68035b686f5a",
+    ]
+    bogus_swhids = [s[:20] + "c0ffee" + s[26:] for s in known_swhids]
+    all_swhids = known_swhids + bogus_swhids
+
+    known_res = web_api_client.known(all_swhids)
+
+    assert {str(k) for k in known_res} == set(all_swhids)
+    for swhid, info in known_res.items():
+        assert info["known"] == (str(swhid) in known_swhids)
+
+
 def test_get_json(web_api_client, web_api_mock):
     swhids = [
         "swh:1:cnt:fe95a46679d128ff167b7c55df5d02356c5a1ae1",