diff --git a/pixel_bridge/build_defs.bzl b/pixel_bridge/build_defs.bzl
new file mode 100644
index 0000000..14fd0b6
--- /dev/null
+++ b/pixel_bridge/build_defs.bzl
@@ -0,0 +1,18 @@
+"""Build definitions for pixel bridge."""
+
+# Platforms where Rust decoding is unavailable.
+UNSUPPORTED_PLATFORMS_RUST = (
+    "//tools/cc_target_os:chromiumos",
+    "//tools/cc_target_os:darwin",
+    "//tools/cc_target_os:fuchsia",
+    "//tools/cc_target_os:android",
+    "//tools/cc_target_os:wasm",
+    "//tools/cc_target_os:hercules_embedded",
+    "//tools/cc_target_os:platform_ios",
+    "//tools/cc_target_os:platform_tvos",
+    "//tools/cc_target_os:platform_visionos",
+    "//tools/cc_target_os:platform_watchos",
+    "//tools/cc_target_os:mpu64",
+    "//tools/cc_target_os:nestcam_ambarella",
+    "//tools/cc_target_os:windows",
+)