diff --git a/.aztec-sync-commit b/.aztec-sync-commit
index 9ebd1dcccac..f99c7ec7e49 100644
--- a/.aztec-sync-commit
+++ b/.aztec-sync-commit
@@ -1 +1 @@
-10d9ad99200a5897417ff5669763ead4e38d87fa
+1dfbe7bc3bf3c455d8fb6c8b5fe6a96c1edf7af9
diff --git a/aztec_macros/src/utils/errors.rs b/aztec_macros/src/utils/errors.rs
index 5d3a61a51dc..52ee5587559 100644
--- a/aztec_macros/src/utils/errors.rs
+++ b/aztec_macros/src/utils/errors.rs
@@ -23,7 +23,7 @@ impl From<AztecMacroError> for MacroError {
     fn from(err: AztecMacroError) -> Self {
         match err {
             AztecMacroError::AztecDepNotFound {} => MacroError {
-                primary_message: "Aztec dependency not found. Please add aztec as a dependency in your Cargo.toml. For more information go to https://docs.aztec.network/developers/debugging/aztecnr-errors#aztec-dependency-not-found-please-add-aztec-as-a-dependency-in-your-nargotoml".to_owned(),
+                primary_message: "Aztec dependency not found. Please add aztec as a dependency in your Nargo.toml. For more information go to https://docs.aztec.network/developers/debugging/aztecnr-errors#aztec-dependency-not-found-please-add-aztec-as-a-dependency-in-your-nargotoml".to_owned(),
                 secondary_message: None,
                 span: None,
             },
diff --git a/tooling/acvm_cli/src/cli/execute_cmd.rs b/tooling/acvm_cli/src/cli/execute_cmd.rs
index 86e7277451f..4e36dbd1f22 100644
--- a/tooling/acvm_cli/src/cli/execute_cmd.rs
+++ b/tooling/acvm_cli/src/cli/execute_cmd.rs
@@ -6,11 +6,10 @@ use bn254_blackbox_solver::Bn254BlackBoxSolver;
 use clap::Args;
 
 use crate::cli::fs::inputs::{read_bytecode_from_file, read_inputs_from_file};
-use crate::cli::fs::witness::save_witness_to_dir;
 use crate::errors::CliError;
 use nargo::ops::{execute_program, DefaultForeignCallExecutor};
 
-use super::fs::witness::create_output_witness_string;
+use super::fs::witness::{create_output_witness_string, save_witness_to_dir};
 
 /// Executes a circuit to calculate its return value
 #[derive(Debug, Clone, Args)]
@@ -46,9 +45,9 @@ fn run_command(args: ExecuteCommand) -> Result<String, CliError> {
     )?;
     if args.output_witness.is_some() {
         save_witness_to_dir(
-            &output_witness_string,
-            &args.working_directory,
+            output_witness,
             &args.output_witness.unwrap(),
+            &args.working_directory,
         )?;
     }
     Ok(output_witness_string)
diff --git a/tooling/acvm_cli/src/cli/fs/witness.rs b/tooling/acvm_cli/src/cli/fs/witness.rs
index 2daaa5a3a58..30ef4278f4b 100644
--- a/tooling/acvm_cli/src/cli/fs/witness.rs
+++ b/tooling/acvm_cli/src/cli/fs/witness.rs
@@ -5,24 +5,29 @@ use std::{
     path::{Path, PathBuf},
 };
 
-use acvm::acir::native_types::WitnessMap;
+use acvm::acir::native_types::{WitnessMap, WitnessStack};
 
 use crate::errors::{CliError, FilesystemError};
 
-/// Saves the provided output witnesses to a toml file created at the given location
-pub(crate) fn save_witness_to_dir<P: AsRef<Path>>(
-    output_witness: &String,
-    witness_dir: P,
-    file_name: &String,
-) -> Result<PathBuf, FilesystemError> {
-    let witness_path = witness_dir.as_ref().join(file_name);
+fn create_named_dir(named_dir: &Path, name: &str) -> PathBuf {
+    std::fs::create_dir_all(named_dir)
+        .unwrap_or_else(|_| panic!("could not create the `{name}` directory"));
+
+    PathBuf::from(named_dir)
+}
 
-    let mut file = File::create(&witness_path)
-        .map_err(|_| FilesystemError::OutputWitnessCreationFailed(file_name.clone()))?;
-    write!(file, "{}", output_witness)
-        .map_err(|_| FilesystemError::OutputWitnessWriteFailed(file_name.clone()))?;
+fn write_to_file(bytes: &[u8], path: &Path) -> String {
+    let display = path.display();
 
-    Ok(witness_path)
+    let mut file = match File::create(path) {
+        Err(why) => panic!("couldn't create {display}: {why}"),
+        Ok(file) => file,
+    };
+
+    match file.write_all(bytes) {
+        Err(why) => panic!("couldn't write to {display}: {why}"),
+        Ok(_) => display.to_string(),
+    }
 }
 
 /// Creates a toml representation of the provided witness map
@@ -34,3 +39,19 @@ pub(crate) fn create_output_witness_string(witnesses: &WitnessMap) -> Result<Str
 
     toml::to_string(&witness_map).map_err(|_| CliError::OutputWitnessSerializationFailed())
 }
+
+pub(crate) fn save_witness_to_dir<P: AsRef<Path>>(
+    witnesses: WitnessStack,
+    witness_name: &str,
+    witness_dir: P,
+) -> Result<PathBuf, FilesystemError> {
+    create_named_dir(witness_dir.as_ref(), "witness");
+    let witness_path = witness_dir.as_ref().join(witness_name).with_extension("gz");
+
+    let buf: Vec<u8> = witnesses
+        .try_into()
+        .map_err(|_op| FilesystemError::OutputWitnessCreationFailed(witness_name.to_string()))?;
+    write_to_file(buf.as_slice(), &witness_path);
+
+    Ok(witness_path)
+}
diff --git a/tooling/acvm_cli/src/errors.rs b/tooling/acvm_cli/src/errors.rs
index 923046410ea..8bc79347159 100644
--- a/tooling/acvm_cli/src/errors.rs
+++ b/tooling/acvm_cli/src/errors.rs
@@ -20,9 +20,6 @@ pub(crate) enum FilesystemError {
 
     #[error(" Error: failed to create output witness file {0}.")]
     OutputWitnessCreationFailed(String),
-
-    #[error(" Error: failed to write output witness file {0}.")]
-    OutputWitnessWriteFailed(String),
 }
 
 #[derive(Debug, Error)]
diff --git a/tooling/noirc_abi_wasm/build.sh b/tooling/noirc_abi_wasm/build.sh
index 4486a214c9c..58724dee02c 100755
--- a/tooling/noirc_abi_wasm/build.sh
+++ b/tooling/noirc_abi_wasm/build.sh
@@ -25,7 +25,6 @@ function run_if_available {
 require_command jq
 require_command cargo
 require_command wasm-bindgen
-require_command wasm-opt
 
 self_path=$(dirname "$(readlink -f "$0")")
 pname=$(cargo read-manifest | jq -r '.name')
@@ -49,5 +48,5 @@ BROWSER_WASM=${BROWSER_DIR}/${pname}_bg.wasm
 run_or_fail cargo build --lib --release --target $TARGET --package ${pname}
 run_or_fail wasm-bindgen $WASM_BINARY --out-dir $NODE_DIR --typescript --target nodejs
 run_or_fail wasm-bindgen $WASM_BINARY --out-dir $BROWSER_DIR --typescript --target web
-run_or_fail wasm-opt $NODE_WASM -o $NODE_WASM -O
-run_or_fail wasm-opt $BROWSER_WASM -o $BROWSER_WASM -O
+run_if_available wasm-opt $NODE_WASM -o $NODE_WASM -O
+run_if_available wasm-opt $BROWSER_WASM -o $BROWSER_WASM -O
diff --git a/tooling/noirc_abi_wasm/src/lib.rs b/tooling/noirc_abi_wasm/src/lib.rs
index ce15f6d502e..fad5abaebba 100644
--- a/tooling/noirc_abi_wasm/src/lib.rs
+++ b/tooling/noirc_abi_wasm/src/lib.rs
@@ -5,7 +5,7 @@
 // See Cargo.toml for explanation.
 use getrandom as _;
 
-use acvm::acir::native_types::WitnessMap;
+use acvm::acir::native_types::{WitnessMap, WitnessStack};
 use iter_extended::try_btree_map;
 use noirc_abi::{
     errors::InputParserError,
@@ -113,3 +113,12 @@ pub fn abi_decode(abi: JsAbi, witness_map: JsWitnessMap) -> Result<JsValue, JsAb
     <wasm_bindgen::JsValue as JsValueSerdeExt>::from_serde(&return_struct)
         .map_err(|err| err.to_string().into())
 }
+
+#[wasm_bindgen(js_name = serializeWitness)]
+pub fn serialise_witness(witness_map: JsWitnessMap) -> Result<Vec<u8>, JsAbiError> {
+    console_error_panic_hook::set_once();
+    let converted_witness: WitnessMap = witness_map.into();
+    let witness_stack: WitnessStack = converted_witness.into();
+    let output = witness_stack.try_into();
+    output.map_err(|_| JsAbiError::new("Failed to convert to Vec<u8>".to_string()))
+}