diff --git a/.github/workflows/atomic.yml b/.github/workflows/atomic.yml
--- a/.github/workflows/atomic.yml
+++ b/.github/workflows/atomic.yml
@@ -33,3 +33,14 @@ jobs:
       - name: Check inherited Linux ACLs
         if: runner.os == 'Linux'
         run: cargo test -p craft-atomic --locked -- --ignored --nocapture
+
+  wasm:
+    name: Atomic WASM
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: wasm32-unknown-unknown
+      - run: cargo check -p craft-atomic --target wasm32-unknown-unknown
+
diff --git a/crates/atomic/src/lib.rs b/crates/atomic/src/lib.rs
--- a/crates/atomic/src/lib.rs
+++ b/crates/atomic/src/lib.rs
@@ -539,7 +539,11 @@ pub fn temp_name(file: &str) -> String {
     static COUNTER: AtomicU64 = AtomicU64::new(0);
     let n = COUNTER.fetch_add(1, Ordering::Relaxed);
     let stem: String = file.chars().take(64).collect();
-    format!(".{stem}.{}-{n}.craft_tmp", std::process::id())
+    #[cfg(not(target_arch = "wasm32"))]
+    let pid = std::process::id();
+    #[cfg(target_arch = "wasm32")]
+    let pid = 0;
+    format!(".{stem}.{pid}-{n}.craft_tmp")
 }
 
 /// The end of an error message: whether an original file was left as it was.
@@ -602,7 +606,11 @@ mod tests {
     impl TempDir {
         fn new(tag: &str) -> Self {
             static N: AtomicU64 = AtomicU64::new(0);
-            let d = std::env::temp_dir().join(format!("craft-atomic-{tag}-{}-{}", std::process::id(), N.fetch_add(1, Ordering::Relaxed)));
+            #[cfg(not(target_arch = "wasm32"))]
+            let pid = std::process::id();
+            #[cfg(target_arch = "wasm32")]
+            let pid = 0;
+            let d = std::env::temp_dir().join(format!("craft-atomic-{tag}-{pid}-{}", N.fetch_add(1, Ordering::Relaxed)));
             let _ = std::fs::remove_dir_all(&d);
             std::fs::create_dir_all(&d).ok();
             Self(d)
@@ -1140,4 +1148,18 @@ mod tests {
         assert_eq!(std::fs::read(&p).ok(), Some(b"best effort data".to_vec()));
         assert_no_temp(&d.0);
     }
+
+    #[test]
+    fn temp_name_format_is_valid() {
+        let name = temp_name("document.craft");
+        assert!(name.starts_with(".document.craft."));
+        assert!(name.ends_with(".craft_tmp"));
+    }
+
+    #[cfg(target_arch = "wasm32")]
+    #[test]
+    fn wasm_atomic_write_returns_unsupported() {
+        let err = atomic_write(Path::new("dummy.craft"), b"data").unwrap_err();
+        assert_eq!(err.kind(), io::ErrorKind::Unsupported);
+    }
 }