diff --git a/css/types/attr.json b/css/types/attr.json
index 016dfc926c5d99..136525e6ae8922 100644
--- a/css/types/attr.json
+++ b/css/types/attr.json
@@ -45,6 +45,51 @@
             "deprecated": false
           }
         },
+        "attr-name_accepts_namespaces": {
+          "__compat": {
+            "description": "`<attr-name>` accepts namespaces",
+            "mdn_url": "https://developer.mozilla.org/docs/Web/CSS/Reference/Values/attr#namespaces",
+            "spec_url": "https://drafts.csswg.org/css-values-5/#typedef-attr-name:~:text=namespaced%20attributes",
+            "tags": [
+              "web-features:attr"
+            ],
+            "support": {
+              "chrome": {
+                "version_added": false,
+                "impl_url": "https://crbug.com/387281256"
+              },
+              "chrome_android": "mirror",
+              "edge": "mirror",
+              "firefox": {
+                "version_added": "150",
+                "flags": [
+                  {
+                    "type": "preference",
+                    "name": "layout.css.attr.enabled",
+                    "value_to_set": "true"
+                  }
+                ]
+              },
+              "firefox_android": "mirror",
+              "oculus": "mirror",
+              "opera": "mirror",
+              "opera_android": "mirror",
+              "safari": {
+                "version_added": false,
+                "impl_url": "https://webkit.org/b/283279"
+              },
+              "safari_ios": "mirror",
+              "samsunginternet_android": "mirror",
+              "webview_android": "mirror",
+              "webview_ios": "mirror"
+            },
+            "status": {
+              "experimental": true,
+              "standard_track": true,
+              "deprecated": false
+            }
+          }
+        },
         "declaration-value": {
           "__compat": {
             "description": "`<declaration-value>`",