diff --git a/CHANGES.md b/CHANGES.md
index 7077d664f..c1020119d 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -2,6 +2,8 @@
 
 ## [Unreleased]
 
+- remove support of `cql-json` in Filter extension
+
 ## [5.2.1] - 2025-04-18
 
 ### Fixed
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/request.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/request.py
index 521026eff..08514e4fc 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/request.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/request.py
@@ -9,7 +9,7 @@
 
 from stac_fastapi.types.search import APIRequest
 
-FilterLang = Literal["cql-json", "cql2-json", "cql2-text"]
+FilterLang = Literal["cql2-json", "cql2-text"]
 
 
 @attr.s
@@ -20,9 +20,9 @@ class FilterExtensionGetRequest(APIRequest):
         Optional[str],
         Query(
             alias="filter",
-            description="""A CQL filter expression for filtering items.\n
-Supports `CQL-JSON` as defined in https://portal.ogc.org/files/96288\n
-Remember to URL encode the CQL-JSON if using GET""",
+            description="""A CQL2 filter expression for filtering items.\n
+Supports `CQL2-JSON` as defined in https://docs.ogc.org/is/21-065r2/21-065r2.htmln
+Remember to URL encode the CQL2-JSON if using GET""",
             openapi_examples={
                 "user-provided": {"value": None},
                 "landsat8-item": {
@@ -83,7 +83,7 @@ class FilterExtensionPostRequest(BaseModel):
         alias="filter-crs",
         description="The coordinate reference system (CRS) used by spatial literals in the 'filter' value. Default is `http://www.opengis.net/def/crs/OGC/1.3/CRS84`",  # noqa: E501
     )
-    filter_lang: Optional[Literal["cql-json", "cql2-json"]] = Field(
+    filter_lang: Optional[Literal["cql2-json"]] = Field(
         "cql2-json",
         alias="filter-lang",
         description="The CQL filter encoding that the 'filter' value uses.",
diff --git a/stac_fastapi/extensions/tests/test_filter.py b/stac_fastapi/extensions/tests/test_filter.py
index 8dc485e67..ba1c1ece8 100644
--- a/stac_fastapi/extensions/tests/test_filter.py
+++ b/stac_fastapi/extensions/tests/test_filter.py
@@ -122,26 +122,6 @@ def test_search_filter_post_filter_lang_default(client_name, request):
     assert response_dict["filter_lang"] == "cql2-json"
 
 
-@pytest.mark.parametrize("client_name", ["client", "client_multit_ext"])
-def test_search_filter_post_filter_lang_non_default(client_name, request):
-    """Test search POST endpoint with filter ext."""
-    client = request.getfixturevalue(client_name)
-
-    filter_lang_value = "cql-json"
-    response = client.post(
-        "/search",
-        json={
-            "collections": ["test"],
-            "filter": {"eq": [{"property": "test_property"}, "test-value"]},
-            "filter-lang": filter_lang_value,
-        },
-    )
-    assert response.is_success, response.json()
-    response_dict = response.json()
-    assert response_dict["filter_expr"]
-    assert response_dict["filter_lang"] == filter_lang_value
-
-
 @pytest.mark.parametrize("client_name", ["client", "client_multit_ext"])
 def test_search_filter_get(client_name, request):
     """Test search GET endpoint with filter ext."""