diff --git a/webextensions/api/runtime.json b/webextensions/api/runtime.json
index ce82e1d56be725..3d610ddedc2a15 100644
--- a/webextensions/api/runtime.json
+++ b/webextensions/api/runtime.json
@@ -331,6 +331,88 @@
                 "version_added": "15"
               }
             }
+          },
+          "aarch64": {
+            "__compat": {
+              "support": {
+                "chrome": {
+                  "version_added": false
+                },
+                "edge": "mirror",
+                "firefox": {
+                  "version_added": "45"
+                },
+                "firefox_android": {
+                  "version_added": "48",
+                  "notes": "Equivalent of `arm64` on Chrome."
+                },
+                "opera": "mirror",
+                "safari": {
+                  "version_added": false
+                },
+                "safari_ios": "mirror"
+              }
+            }
+          },
+          "arm64": {
+            "__compat": {
+              "support": {
+                "chrome": {
+                  "version_added": "≤58",
+                  "notes": "Equivalent of `aarch64` on Firefox."
+                },
+                "edge": "mirror",
+                "firefox": {
+                  "version_added": false
+                },
+                "firefox_android": "mirror",
+                "opera": "mirror",
+                "safari": {
+                  "version_added": false
+                },
+                "safari_ios": "mirror"
+              }
+            }
+          },
+          "mips": {
+            "__compat": {
+              "support": {
+                "chrome": {
+                  "version_added": "≤58",
+                  "notes": "Not supported on any official Chrome release."
+                },
+                "edge": "mirror",
+                "firefox": {
+                  "version_added": false
+                },
+                "firefox_android": "mirror",
+                "opera": "mirror",
+                "safari": {
+                  "version_added": false
+                },
+                "safari_ios": "mirror"
+              }
+            }
+          },
+          "mips64": {
+            "__compat": {
+              "support": {
+                "chrome": {
+                  "version_added": "≤58",
+                  "notes": "Not supported on any official Chrome release."
+                },
+                "edge": "mirror",
+                "firefox": {
+                  "version_added": false
+                },
+                "firefox_android": "mirror",
+                "opera": "mirror",
+                "safari": {
+                  "version_added": false
+                },
+                "safari_ios": "mirror"
+              }
+            }
           }
         },
         "PlatformInfo": {