diff --git a/crates/moon/tests/cmd_test.rs b/crates/moon/tests/cmd_test.rs
index b0a369ff..c63aaf2b 100644
--- a/crates/moon/tests/cmd_test.rs
+++ b/crates/moon/tests/cmd_test.rs
@@ -117,6 +117,7 @@ fn cmd_test() {
     all_results.sort();
     expect_test::expect![[r#"
         [
+            ${WORK_DIR}/cond_comp.in/moon.test, ok,
             ${WORK_DIR}/moon_build_package.in/moon.test, ok,
             ${WORK_DIR}/moon_info_001.in/moon.test, ok,
             ${WORK_DIR}/moon_info_002.in/moon.test, ok,
diff --git a/crates/moon/tests/test_cases/cond_comp.in/moon.test b/crates/moon/tests/test_cases/cond_comp.in/moon.test
new file mode 100644
index 00000000..fcd18171
--- /dev/null
+++ b/crates/moon/tests/test_cases/cond_comp.in/moon.test
@@ -0,0 +1,54 @@
+  $ moon build --dry-run --sort-input --nostd
+  moonc build-package ./src/lib/all.mbt ./src/lib/not_js.mbt -o ./target/wasm-gc/release/build/lib/lib.core -pkg username/hello/lib -pkg-sources username/hello/lib:./src/lib -target wasm-gc
+  moonc build-package ./src/main/main.mbt -o ./target/wasm-gc/release/build/main/main.core -pkg username/hello/main -is-main -i ./target/wasm-gc/release/build/lib/lib.mi:lib -pkg-sources username/hello/main:./src/main -target wasm-gc
+  moonc link-core ./target/wasm-gc/release/build/lib/lib.core ./target/wasm-gc/release/build/main/main.core -main username/hello/main -o ./target/wasm-gc/release/build/main/main.wasm -pkg-sources username/hello/lib:./src/lib -pkg-sources username/hello/main:./src/main -target wasm-gc
+  
+  $ moon build --target wasm --dry-run --sort-input --nostd
+  moonc build-package ./src/lib/all.mbt ./src/lib/not_js.mbt -o ./target/wasm/release/build/lib/lib.core -pkg username/hello/lib -pkg-sources username/hello/lib:./src/lib -target wasm
+  moonc build-package ./src/main/main.mbt -o ./target/wasm/release/build/main/main.core -pkg username/hello/main -is-main -i ./target/wasm/release/build/lib/lib.mi:lib -pkg-sources username/hello/main:./src/main -target wasm
+  moonc link-core ./target/wasm/release/build/lib/lib.core ./target/wasm/release/build/main/main.core -main username/hello/main -o ./target/wasm/release/build/main/main.wasm -pkg-sources username/hello/lib:./src/lib -pkg-sources username/hello/main:./src/main -target wasm
+  
+  $ moon build --target wasm-gc --dry-run --sort-input --nostd
+  moonc build-package ./src/lib/all.mbt ./src/lib/not_js.mbt -o ./target/wasm-gc/release/build/lib/lib.core -pkg username/hello/lib -pkg-sources username/hello/lib:./src/lib -target wasm-gc
+  moonc build-package ./src/main/main.mbt -o ./target/wasm-gc/release/build/main/main.core -pkg username/hello/main -is-main -i ./target/wasm-gc/release/build/lib/lib.mi:lib -pkg-sources username/hello/main:./src/main -target wasm-gc
+  moonc link-core ./target/wasm-gc/release/build/lib/lib.core ./target/wasm-gc/release/build/main/main.core -main username/hello/main -o ./target/wasm-gc/release/build/main/main.wasm -pkg-sources username/hello/lib:./src/lib -pkg-sources username/hello/main:./src/main -target wasm-gc
+  
+  $ moon build --dry-run --target js --sort-input --nostd
+  moonc build-package ./src/lib/all.mbt ./src/lib/js_and_release.mbt ./src/lib/only_js.mbt -o ./target/js/release/build/lib/lib.core -pkg username/hello/lib -pkg-sources username/hello/lib:./src/lib -target js
+  moonc build-package ./src/main/main.mbt -o ./target/js/release/build/main/main.core -pkg username/hello/main -is-main -i ./target/js/release/build/lib/lib.mi:lib -pkg-sources username/hello/main:./src/main -target js
+  moonc link-core ./target/js/release/build/lib/lib.core ./target/js/release/build/main/main.core -main username/hello/main -o ./target/js/release/build/main/main.js -pkg-sources username/hello/lib:./src/lib -pkg-sources username/hello/main:./src/main -target js
+  
+  $ moon build --dry-run --target wasm --sort-input --nostd --debug
+  moonc build-package ./src/lib/all.mbt ./src/lib/not_js.mbt ./src/lib/only_debug.mbt -o ./target/wasm/debug/build/lib/lib.core -pkg username/hello/lib -pkg-sources username/hello/lib:./src/lib -target wasm -g
+  moonc build-package ./src/main/main.mbt -o ./target/wasm/debug/build/main/main.core -pkg username/hello/main -is-main -i ./target/wasm/debug/build/lib/lib.mi:lib -pkg-sources username/hello/main:./src/main -target wasm -g
+  moonc link-core ./target/wasm/debug/build/lib/lib.core ./target/wasm/debug/build/main/main.core -main username/hello/main -o ./target/wasm/debug/build/main/main.wasm -pkg-sources username/hello/lib:./src/lib -pkg-sources username/hello/main:./src/main -target wasm -g
+  
+  $ moon build --dry-run --target wasm-gc --sort-input --nostd --debug
+  moonc build-package ./src/lib/all.mbt ./src/lib/not_js.mbt ./src/lib/only_debug.mbt -o ./target/wasm-gc/debug/build/lib/lib.core -pkg username/hello/lib -pkg-sources username/hello/lib:./src/lib -target wasm-gc -g -source-map
+  moonc build-package ./src/main/main.mbt -o ./target/wasm-gc/debug/build/main/main.core -pkg username/hello/main -is-main -i ./target/wasm-gc/debug/build/lib/lib.mi:lib -pkg-sources username/hello/main:./src/main -target wasm-gc -g -source-map
+  moonc link-core ./target/wasm-gc/debug/build/lib/lib.core ./target/wasm-gc/debug/build/main/main.core -main username/hello/main -o ./target/wasm-gc/debug/build/main/main.wasm -pkg-sources username/hello/lib:./src/lib -pkg-sources username/hello/main:./src/main -target wasm-gc -g -source-map
+  
+  $ moon build --dry-run --target js --sort-input --nostd --debug
+  moonc build-package ./src/lib/all.mbt ./src/lib/only_debug.mbt ./src/lib/only_js.mbt -o ./target/js/debug/build/lib/lib.core -pkg username/hello/lib -pkg-sources username/hello/lib:./src/lib -target js -g -source-map
+  moonc build-package ./src/main/main.mbt -o ./target/js/debug/build/main/main.core -pkg username/hello/main -is-main -i ./target/js/debug/build/lib/lib.mi:lib -pkg-sources username/hello/main:./src/main -target js -g -source-map
+  moonc link-core ./target/js/debug/build/lib/lib.core ./target/js/debug/build/main/main.core -main username/hello/main -o ./target/js/debug/build/main/main.js -pkg-sources username/hello/lib:./src/lib -pkg-sources username/hello/main:./src/main -target js -g -source-map
+  
+  $ moon check --dry-run --target js --sort-input --nostd
+  moonc check ./src/lib/all.mbt ./src/lib/js_and_release.mbt ./src/lib/only_js.mbt -o ./target/js/release/check/lib/lib.mi -pkg username/hello/lib -pkg-sources username/hello/lib:./src/lib -target js
+  moonc check ./src/main/main.mbt -o ./target/js/release/check/main/main.mi -pkg username/hello/main -is-main -i ./target/js/release/check/lib/lib.mi:lib -pkg-sources username/hello/main:./src/main -target js
+  moonc check ./src/lib/hello_test.mbt ./src/lib/js_only_test.mbt -o ./target/js/release/check/lib/lib.blackbox_test.mi -pkg username/hello/lib_blackbox_test -i ./target/js/release/check/lib/lib.mi:lib -pkg-sources username/hello/lib_blackbox_test:./src/lib -target js
+  
+  $ moon test --dry-run --target js --sort-input --nostd
+  moon generate-test-driver --source-dir . --target-dir ./target/js/debug/test --package username/hello/lib --sort-input --target js --driver-kind blackbox
+  moonc build-package ./src/lib/all.mbt ./src/lib/only_debug.mbt ./src/lib/only_js.mbt -o ./target/js/debug/test/lib/lib.core -pkg username/hello/lib -pkg-sources username/hello/lib:./src/lib -target js -g
+  moonc build-package ./src/lib/hello_test.mbt ./src/lib/js_only_test.mbt ./target/js/debug/test/lib/__generated_driver_for_blackbox_test.mbt -o ./target/js/debug/test/lib/lib.blackbox_test.core -pkg username/hello/lib_blackbox_test -is-main -i ./target/js/debug/test/lib/lib.mi:lib -pkg-sources username/hello/lib_blackbox_test:./src/lib -target js -g
+  moonc link-core ./target/js/debug/test/lib/lib.core ./target/js/debug/test/lib/lib.blackbox_test.core -main username/hello/lib_blackbox_test -o ./target/js/debug/test/lib/lib.blackbox_test.js -test-mode -pkg-sources username/hello/lib:./src/lib -pkg-sources username/hello/lib_blackbox_test:./src/lib -exported_functions execute -js-format cjs -target js -g
+  moon generate-test-driver --source-dir . --target-dir ./target/js/debug/test --package username/hello/lib --sort-input --target js --driver-kind internal
+  moonc build-package ./src/lib/all.mbt ./src/lib/only_debug.mbt ./src/lib/only_js.mbt ./target/js/debug/test/lib/__generated_driver_for_internal_test.mbt -o ./target/js/debug/test/lib/lib.internal_test.core -pkg username/hello/lib -is-main -pkg-sources username/hello/lib:./src/lib -target js -g
+  moonc link-core ./target/js/debug/test/lib/lib.internal_test.core -main username/hello/lib -o ./target/js/debug/test/lib/lib.internal_test.js -test-mode -pkg-sources username/hello/lib:./src/lib -exported_functions execute -js-format cjs -target js -g
+  
+  $ moon bundle --dry-run --target js --sort-input --nostd
+  moonc build-package ./src/lib/all.mbt ./src/lib/js_and_release.mbt ./src/lib/only_js.mbt -o ./target/js/release/bundle/lib/lib.core -pkg username/hello/lib -pkg-sources username/hello/lib:./lib -target js
+  moonc build-package ./src/main/main.mbt -o ./target/js/release/bundle/main/main.core -pkg username/hello/main -is-main -i ./target/js/release/bundle/lib/lib.mi:lib -pkg-sources username/hello/main:./main -target js
+  moonc bundle-core ./target/js/release/bundle/lib/lib.core ./target/js/release/bundle/main/main.core -o ./target/js/release/bundle/hello.core
+  
diff --git a/crates/moonbuild/template/pkg.schema.json b/crates/moonbuild/template/pkg.schema.json
index fd4306d3..b854372c 100644
--- a/crates/moonbuild/template/pkg.schema.json
+++ b/crates/moonbuild/template/pkg.schema.json
@@ -45,6 +45,19 @@
         "null"
       ]
     },
+    "targets": {
+      "description": "Conditional compilation targets",
+      "type": [
+        "object",
+        "null"
+      ],
+      "additionalProperties": {
+        "type": [
+          "string",
+          "null"
+        ]
+      }
+    },
     "test-import": {
       "description": "Black box test imported packages of the package",
       "anyOf": [
diff --git a/docs/manual/src/source/pkg_json_schema.html b/docs/manual/src/source/pkg_json_schema.html
index 20429220..02936ef4 100644
--- a/docs/manual/src/source/pkg_json_schema.html
+++ b/docs/manual/src/source/pkg_json_schema.html
@@ -83,6 +83,19 @@
         "null"
       ]
     },
+    "targets": {
+      "description": "Conditional compilation targets",
+      "type": [
+        "object",
+        "null"
+      ],
+      "additionalProperties": {
+        "type": [
+          "string",
+          "null"
+        ]
+      }
+    },
     "test-import": {
       "description": "Black box test imported packages of the package",
       "anyOf": [