diff --git a/components/script/dom/bindings/refcounted.rs b/components/script/dom/bindings/refcounted.rs
index cdf80264edb..b449a984356 100644
--- a/components/script/dom/bindings/refcounted.rs
+++ b/components/script/dom/bindings/refcounted.rs
@@ -122,7 +122,7 @@ impl TrustedPromise {
 
     /// A task which will reject the promise.
     #[allow(unrooted_must_root)]
-    pub fn reject_task(self, error: Error) -> impl Send + Task {
+    pub fn reject_task(self, error: Error) -> impl Task {
         let this = self;
         task!(reject_promise: move || {
             debug!("Rejecting promise.");
@@ -135,7 +135,7 @@ impl TrustedPromise {
 
     /// A task which will resolve the promise.
     #[allow(unrooted_must_root)]
-    pub fn resolve_task<T>(self, value: T) -> impl Send + Task
+    pub fn resolve_task<T>(self, value: T) -> impl Task
     where
         T: ToJSValConvertible + Send,
     {
diff --git a/components/script/dom/worklet.rs b/components/script/dom/worklet.rs
index b55f9d328a0..e6d47d42f48 100644
--- a/components/script/dom/worklet.rs
+++ b/components/script/dom/worklet.rs
@@ -645,8 +645,9 @@ impl WorkletThread {
     }
 
     /// Run a task in the main script thread.
-    fn run_in_script_thread<T>(&self, task: T) where
-        T: 'static + Send + Task,
+    fn run_in_script_thread<T>(&self, task: T)
+    where
+        T: Task + 'static,
     {
         let msg = CommonScriptMsg::Task(ScriptThreadEventCategory::WorkletEvent, box task);
         let msg = MainThreadScriptMsg::Common(msg);
diff --git a/components/script/script_runtime.rs b/components/script/script_runtime.rs
index 270dd0cdafe..45f3d6a7ea3 100644
--- a/components/script/script_runtime.rs
+++ b/components/script/script_runtime.rs
@@ -44,7 +44,7 @@ pub enum CommonScriptMsg {
     /// supplied channel.
     CollectReports(ReportsChan),
     /// Generic message that encapsulates event handling.
-    Task(ScriptThreadEventCategory, Box<Task + Send>),
+    Task(ScriptThreadEventCategory, Box<Task>),
 }
 
 impl fmt::Debug for CommonScriptMsg {
diff --git a/components/script/task.rs b/components/script/task.rs
index 08f5c499aa6..dcefd31a162 100644
--- a/components/script/task.rs
+++ b/components/script/task.rs
@@ -15,7 +15,7 @@ macro_rules! task {
         struct $name<F>(F);
         impl<F> ::task::Task for $name<F>
         where
-            F: ::std::ops::FnOnce(),
+            F: ::std::ops::FnOnce() + Send,
         {
             fn name(&self) -> &'static str {
                 stringify!($name)
@@ -30,13 +30,13 @@ macro_rules! task {
 }
 
 /// A task that can be run. The name method is for profiling purposes.
-pub trait Task {
+pub trait Task: Send {
     #[allow(unsafe_code)]
     fn name(&self) -> &'static str { unsafe { intrinsics::type_name::<Self>() } }
     fn run(self: Box<Self>);
 }
 
-impl fmt::Debug for Task + Send {
+impl fmt::Debug for Task {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         fmt.debug_tuple(self.name()).field(&format_args!("...")).finish()
     }
@@ -50,9 +50,9 @@ pub struct TaskCanceller {
 impl TaskCanceller {
     /// Returns a wrapped `task` that will be cancelled if the `TaskCanceller`
     /// says so.
-    pub fn wrap_task<T>(&self, task: Box<T>) -> Box<Task + Send>
+    pub fn wrap_task<T>(&self, task: Box<T>) -> Box<Task>
     where
-        T: Send + Task + 'static,
+        T: Task + 'static,
     {
         box CancellableTask {
             cancelled: self.cancelled.clone(),
@@ -62,14 +62,14 @@ impl TaskCanceller {
 }
 
 /// A task that can be cancelled by toggling a shared flag.
-pub struct CancellableTask<T: Send + Task> {
+pub struct CancellableTask<T: Task> {
     cancelled: Option<Arc<AtomicBool>>,
     inner: Box<T>,
 }
 
 impl<T> CancellableTask<T>
 where
-    T: Send + Task,
+    T: Task,
 {
     fn is_cancelled(&self) -> bool {
         self.cancelled.as_ref().map_or(false, |cancelled| {
@@ -80,7 +80,7 @@ where
 
 impl<T> Task for CancellableTask<T>
 where
-    T: Send + Task,
+    T: Task,
 {
     fn name(&self) -> &'static str {
         self.inner.name()
diff --git a/components/script/task_source/dom_manipulation.rs b/components/script/task_source/dom_manipulation.rs
index 93cdfde95f4..4062b5b1495 100644
--- a/components/script/task_source/dom_manipulation.rs
+++ b/components/script/task_source/dom_manipulation.rs
@@ -32,7 +32,7 @@ impl TaskSource for DOMManipulationTaskSource {
         canceller: &TaskCanceller,
     ) -> Result<(), ()>
     where
-        T: Task + Send + 'static,
+        T: Task + 'static,
     {
         let msg = MainThreadScriptMsg::Common(CommonScriptMsg::Task(
             ScriptThreadEventCategory::ScriptEvent,
diff --git a/components/script/task_source/file_reading.rs b/components/script/task_source/file_reading.rs
index 1d44a4087d6..111f07ddba1 100644
--- a/components/script/task_source/file_reading.rs
+++ b/components/script/task_source/file_reading.rs
@@ -25,7 +25,7 @@ impl TaskSource for FileReadingTaskSource {
         canceller: &TaskCanceller,
     ) -> Result<(), ()>
     where
-        T: Send + Task + 'static,
+        T: Task + 'static,
     {
         self.0.send(CommonScriptMsg::Task(
             ScriptThreadEventCategory::FileRead,
diff --git a/components/script/task_source/mod.rs b/components/script/task_source/mod.rs
index 40b3c2f3261..3c6139b6df3 100644
--- a/components/script/task_source/mod.rs
+++ b/components/script/task_source/mod.rs
@@ -20,9 +20,12 @@ pub trait TaskSource {
         canceller: &TaskCanceller,
     ) -> Result<(), ()>
     where
-        T: Send + Task + 'static;
+        T: Task + 'static;
 
-    fn queue<T: Task + Send + 'static>(&self, msg: Box<T>, global: &GlobalScope) -> Result<(), ()> {
+    fn queue<T>(&self, msg: Box<T>, global: &GlobalScope) -> Result<(), ()>
+    where
+        T: Task + 'static,
+    {
         self.queue_with_canceller(msg, &global.task_canceller())
     }
 }
diff --git a/components/script/task_source/networking.rs b/components/script/task_source/networking.rs
index 5d339037729..57dabbbfd39 100644
--- a/components/script/task_source/networking.rs
+++ b/components/script/task_source/networking.rs
@@ -22,7 +22,7 @@ impl TaskSource for NetworkingTaskSource {
         canceller: &TaskCanceller,
     ) -> Result<(), ()>
     where
-        T: Send + Task + 'static,
+        T: Task + 'static,
     {
         self.0.send(CommonScriptMsg::Task(
             ScriptThreadEventCategory::NetworkEvent,
@@ -36,7 +36,7 @@ impl NetworkingTaskSource {
     /// global scope gets destroyed.
     pub fn queue_unconditionally<T>(&self, msg: Box<T>) -> Result<(), ()>
     where
-        T: Task + Send + 'static,
+        T: Task + 'static,
     {
         self.0.send(CommonScriptMsg::Task(ScriptThreadEventCategory::NetworkEvent, msg))
     }
diff --git a/components/script/task_source/performance_timeline.rs b/components/script/task_source/performance_timeline.rs
index 0b379d496f4..0bac66270f6 100644
--- a/components/script/task_source/performance_timeline.rs
+++ b/components/script/task_source/performance_timeline.rs
@@ -36,7 +36,7 @@ impl TaskSource for PerformanceTimelineTaskSource {
         canceller: &TaskCanceller,
     ) -> Result<(), ()>
     where
-        T: Send + Task + 'static,
+        T: Task + 'static,
     {
         let msg = CommonScriptMsg::Task(
             ScriptThreadEventCategory::PerformanceTimelineTask,
diff --git a/components/script/task_source/user_interaction.rs b/components/script/task_source/user_interaction.rs
index 8b36a61e9d0..76321e0fa10 100644
--- a/components/script/task_source/user_interaction.rs
+++ b/components/script/task_source/user_interaction.rs
@@ -32,7 +32,7 @@ impl TaskSource for UserInteractionTaskSource {
         canceller: &TaskCanceller,
     ) -> Result<(), ()>
     where
-        T: Task + Send + 'static,
+        T: Task + 'static,
     {
         let msg = MainThreadScriptMsg::Common(CommonScriptMsg::Task(
             ScriptThreadEventCategory::InputEvent,