diff --git a/cli/main.rs b/cli/main.rs
index f94e329e2251c1..7c6265fb40bf23 100644
--- a/cli/main.rs
+++ b/cli/main.rs
@@ -127,6 +127,7 @@ fn create_web_worker_callback(ps: ProcState) -> Arc<CreateWebWorkerCb> {
         ts_version: version::TYPESCRIPT.to_string(),
         unstable: ps.flags.unstable,
       },
+      extensions: vec![],
       unsafely_ignore_certificate_errors: ps
         .flags
         .unsafely_ignore_certificate_errors
@@ -216,6 +217,7 @@ pub fn create_main_worker(
       ts_version: version::TYPESCRIPT.to_string(),
       unstable: ps.flags.unstable,
     },
+    extensions: vec![],
     unsafely_ignore_certificate_errors: ps
       .flags
       .unsafely_ignore_certificate_errors
diff --git a/cli/standalone.rs b/cli/standalone.rs
index 2e4704ea9c17c0..819ba10a4984c6 100644
--- a/cli/standalone.rs
+++ b/cli/standalone.rs
@@ -241,6 +241,7 @@ pub async fn run(
       ts_version: version::TYPESCRIPT.to_string(),
       unstable: metadata.unstable,
     },
+    extensions: vec![],
     user_agent: version::get_user_agent(),
     unsafely_ignore_certificate_errors: metadata
       .unsafely_ignore_certificate_errors,
diff --git a/runtime/examples/hello_runtime.rs b/runtime/examples/hello_runtime.rs
index eb4557c049a81e..5ff482c5641c93 100644
--- a/runtime/examples/hello_runtime.rs
+++ b/runtime/examples/hello_runtime.rs
@@ -36,6 +36,7 @@ async fn main() -> Result<(), AnyError> {
       ts_version: "x".to_string(),
       unstable: false,
     },
+    extensions: vec![],
     unsafely_ignore_certificate_errors: None,
     root_cert_store: None,
     user_agent: "hello_runtime".to_string(),
diff --git a/runtime/web_worker.rs b/runtime/web_worker.rs
index 3db74dc578fa47..e269110de9da02 100644
--- a/runtime/web_worker.rs
+++ b/runtime/web_worker.rs
@@ -260,6 +260,7 @@ pub struct WebWorker {
 
 pub struct WebWorkerOptions {
   pub bootstrap: BootstrapOptions,
+  pub extensions: Vec<Extension>,
   pub unsafely_ignore_certificate_errors: Option<Vec<String>>,
   pub root_cert_store: Option<RootCertStore>,
   pub user_agent: String,
@@ -297,7 +298,7 @@ impl WebWorker {
     permissions: Permissions,
     main_module: ModuleSpecifier,
     worker_id: WorkerId,
-    options: WebWorkerOptions,
+    mut options: WebWorkerOptions,
   ) -> (Self, SendableWebWorkerHandle) {
     // Permissions: many ops depend on this
     let unstable = options.bootstrap.unstable;
@@ -377,6 +378,7 @@ impl WebWorker {
     // Append exts
     extensions.extend(runtime_exts);
     extensions.extend(deno_ns_exts); // May be empty
+    extensions.extend(std::mem::take(&mut options.extensions));
 
     let mut js_runtime = JsRuntime::new(RuntimeOptions {
       module_loader: Some(options.module_loader.clone()),
diff --git a/runtime/worker.rs b/runtime/worker.rs
index 8327c0dd9467c9..e1b9599a381da8 100644
--- a/runtime/worker.rs
+++ b/runtime/worker.rs
@@ -44,6 +44,7 @@ pub struct MainWorker {
 
 pub struct WorkerOptions {
   pub bootstrap: BootstrapOptions,
+  pub extensions: Vec<Extension>,
   pub unsafely_ignore_certificate_errors: Option<Vec<String>>,
   pub root_cert_store: Option<RootCertStore>,
   pub user_agent: String,
@@ -77,7 +78,7 @@ impl MainWorker {
   pub fn from_options(
     main_module: ModuleSpecifier,
     permissions: Permissions,
-    options: WorkerOptions,
+    mut options: WorkerOptions,
   ) -> Self {
     // Permissions: many ops depend on this
     let unstable = options.bootstrap.unstable;
@@ -92,7 +93,7 @@ impl MainWorker {
       .build();
 
     // Internal modules
-    let extensions: Vec<Extension> = vec![
+    let mut extensions: Vec<Extension> = vec![
       // Web APIs
       deno_webidl::init(),
       deno_console::init(),
@@ -146,6 +147,7 @@ impl MainWorker {
       // Permissions ext (worker specific state)
       perm_ext,
     ];
+    extensions.extend(std::mem::take(&mut options.extensions));
 
     let mut js_runtime = JsRuntime::new(RuntimeOptions {
       module_loader: Some(options.module_loader.clone()),
@@ -313,6 +315,7 @@ mod tests {
         ts_version: "x".to_string(),
         unstable: false,
       },
+      extensions: vec![],
       user_agent: "x".to_string(),
       unsafely_ignore_certificate_errors: None,
       root_cert_store: None,