diff --git a/testing/web-platform/meta/MANIFEST.json b/testing/web-platform/meta/MANIFEST.json
index 010b2a61a33e3..fb7e818801389 100644
--- a/testing/web-platform/meta/MANIFEST.json
+++ b/testing/web-platform/meta/MANIFEST.json
@@ -1810185,6 +1810185,34 @@ resources
 /
 postmessage
 -
+dictionary
+-
+transferables
+-
+worker
+.
+js
+"
+:
+[
+[
+{
+}
+]
+]
+"
+service
+-
+workers
+/
+service
+-
+worker
+/
+resources
+/
+postmessage
+-
 msgport
 -
 to
@@ -2545694,6 +2545722,40 @@ message
 -
 channels
 /
+dictionary
+-
+transferrable
+.
+html
+"
+:
+[
+[
+"
+/
+webmessaging
+/
+message
+-
+channels
+/
+dictionary
+-
+transferrable
+.
+html
+"
+{
+}
+]
+]
+"
+webmessaging
+/
+message
+-
+channels
+/
 worker
 .
 html
@@ -2569402,6 +2569464,48 @@ second
 -
 argument
 -
+dictionary
+.
+html
+"
+:
+[
+[
+"
+/
+workers
+/
+interfaces
+/
+DedicatedWorkerGlobalScope
+/
+postMessage
+/
+second
+-
+argument
+-
+dictionary
+.
+html
+"
+{
+}
+]
+]
+"
+workers
+/
+interfaces
+/
+DedicatedWorkerGlobalScope
+/
+postMessage
+/
+second
+-
+argument
+-
 null
 -
 in
@@ -4226478,7 +4226582,7 @@ html
 :
 [
 "
-6b2f6d78e12210647a47e2eb317c6387e8487ca2
+3d73afe9796114f42e614292ef4b180dd78cdee5
 "
 "
 testharness
@@ -4233175,6 +4233279,36 @@ resources
 /
 postmessage
 -
+dictionary
+-
+transferables
+-
+worker
+.
+js
+"
+:
+[
+"
+87a4500d754ab02465e109899e7f1ffdc0bdca53
+"
+"
+support
+"
+]
+"
+service
+-
+workers
+/
+service
+-
+worker
+/
+resources
+/
+postmessage
+-
 msgport
 -
 to
@@ -4331954,6 +4332088,28 @@ message
 -
 channels
 /
+dictionary
+-
+transferrable
+.
+html
+"
+:
+[
+"
+f7ab1086f7e7978f00a4901d7aa47d8675ee1373
+"
+"
+testharness
+"
+]
+"
+webmessaging
+/
+message
+-
+channels
+/
 worker
 .
 html
@@ -4367643,6 +4367799,32 @@ second
 -
 argument
 -
+dictionary
+.
+html
+"
+:
+[
+"
+e086dc13db658ef7e87a3046a89c5d85bd25cca7
+"
+"
+testharness
+"
+]
+"
+workers
+/
+interfaces
+/
+DedicatedWorkerGlobalScope
+/
+postMessage
+/
+second
+-
+argument
+-
 null
 -
 in
@@ -4367680,7 +4367862,7 @@ html
 :
 [
 "
-e81a56bad3d3d11193194777f7342c8fc190e512
+4a03c830a29fb2937bc07cc50ed167201bd8486f
 "
 "
 testharness
diff --git a/testing/web-platform/tests/service-workers/service-worker/postmessage.https.html b/testing/web-platform/tests/service-workers/service-worker/postmessage.https.html
index 4d01140c2bd85..ea03cefb71d22 100644
--- a/testing/web-platform/tests/service-workers/service-worker/postmessage.https.html
+++ b/testing/web-platform/tests/service-workers/service-worker/postmessage.https.html
@@ -1322,6 +1322,362 @@
 '
 )
 ;
+promise_test
+(
+t
+=
+>
+{
+var
+script
+=
+'
+resources
+/
+postmessage
+-
+dictionary
+-
+transferables
+-
+worker
+.
+js
+'
+;
+var
+scope
+=
+'
+resources
+/
+blank
+.
+html
+'
+;
+var
+sw
+=
+navigator
+.
+serviceWorker
+;
+var
+message
+=
+'
+Hello
+world
+!
+'
+;
+var
+text_encoder
+=
+new
+TextEncoder
+;
+var
+text_decoder
+=
+new
+TextDecoder
+;
+return
+service_worker_unregister_and_register
+(
+t
+script
+scope
+)
+.
+then
+(
+r
+=
+>
+{
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+r
+.
+unregister
+(
+)
+)
+;
+var
+ab
+=
+text_encoder
+.
+encode
+(
+message
+)
+;
+assert_equals
+(
+ab
+.
+byteLength
+message
+.
+length
+)
+;
+r
+.
+installing
+.
+postMessage
+(
+ab
+{
+transfer
+:
+[
+ab
+.
+buffer
+]
+}
+)
+;
+assert_equals
+(
+text_decoder
+.
+decode
+(
+ab
+)
+'
+'
+)
+;
+assert_equals
+(
+ab
+.
+byteLength
+0
+)
+;
+return
+new
+Promise
+(
+resolve
+=
+>
+{
+sw
+.
+onmessage
+=
+resolve
+;
+}
+)
+;
+}
+)
+.
+then
+(
+e
+=
+>
+{
+/
+/
+Verify
+the
+integrity
+of
+the
+transferred
+array
+buffer
+.
+assert_equals
+(
+e
+.
+data
+.
+content
+message
+)
+;
+assert_equals
+(
+e
+.
+data
+.
+byteLength
+message
+.
+length
+)
+;
+return
+new
+Promise
+(
+resolve
+=
+>
+{
+sw
+.
+onmessage
+=
+resolve
+;
+}
+)
+;
+}
+)
+.
+then
+(
+e
+=
+>
+{
+/
+/
+Verify
+the
+integrity
+of
+the
+array
+buffer
+sent
+back
+from
+/
+/
+ServiceWorker
+via
+Client
+.
+postMessage
+.
+assert_equals
+(
+text_decoder
+.
+decode
+(
+e
+.
+data
+)
+message
+)
+;
+assert_equals
+(
+e
+.
+data
+.
+byteLength
+message
+.
+length
+)
+;
+return
+new
+Promise
+(
+resolve
+=
+>
+{
+sw
+.
+onmessage
+=
+resolve
+;
+}
+)
+;
+}
+)
+.
+then
+(
+e
+=
+>
+{
+/
+/
+Verify
+that
+the
+array
+buffer
+on
+ServiceWorker
+is
+neutered
+.
+assert_equals
+(
+e
+.
+data
+.
+content
+'
+'
+)
+;
+assert_equals
+(
+e
+.
+data
+.
+byteLength
+0
+)
+;
+}
+)
+;
+}
+'
+postMessage
+with
+dictionary
+a
+transferable
+ArrayBuffer
+between
+ServiceWorker
+and
+Client
+'
+)
+;
 <
 /
 script
diff --git a/testing/web-platform/tests/service-workers/service-worker/resources/postmessage-dictionary-transferables-worker.js b/testing/web-platform/tests/service-workers/service-worker/resources/postmessage-dictionary-transferables-worker.js
new file mode 100644
index 0000000000000..b810f3ddde6e7
--- /dev/null
+++ b/testing/web-platform/tests/service-workers/service-worker/resources/postmessage-dictionary-transferables-worker.js
@@ -0,0 +1,165 @@
+var
+messageHandler
+=
+function
+(
+port
+e
+)
+{
+var
+text_decoder
+=
+new
+TextDecoder
+;
+port
+.
+postMessage
+(
+{
+content
+:
+text_decoder
+.
+decode
+(
+e
+.
+data
+)
+byteLength
+:
+e
+.
+data
+.
+byteLength
+}
+)
+;
+/
+/
+Send
+back
+the
+array
+buffer
+via
+Client
+.
+postMessage
+.
+port
+.
+postMessage
+(
+e
+.
+data
+{
+transfer
+:
+[
+e
+.
+data
+.
+buffer
+]
+}
+)
+;
+port
+.
+postMessage
+(
+{
+content
+:
+text_decoder
+.
+decode
+(
+e
+.
+data
+)
+byteLength
+:
+e
+.
+data
+.
+byteLength
+}
+)
+;
+}
+;
+self
+.
+addEventListener
+(
+'
+message
+'
+e
+=
+>
+{
+if
+(
+e
+.
+ports
+[
+0
+]
+)
+{
+/
+/
+Wait
+for
+messages
+sent
+via
+MessagePort
+.
+e
+.
+ports
+[
+0
+]
+.
+onmessage
+=
+messageHandler
+.
+bind
+(
+null
+e
+.
+ports
+[
+0
+]
+)
+;
+return
+;
+}
+messageHandler
+(
+e
+.
+source
+e
+)
+;
+}
+)
+;
diff --git a/testing/web-platform/tests/webmessaging/message-channels/dictionary-transferrable.html b/testing/web-platform/tests/webmessaging/message-channels/dictionary-transferrable.html
new file mode 100644
index 0000000000000..cf4140938ab48
--- /dev/null
+++ b/testing/web-platform/tests/webmessaging/message-channels/dictionary-transferrable.html
@@ -0,0 +1,154 @@
+<
+!
+doctype
+html
+>
+<
+title
+>
+basic
+messagechannel
+with
+transfer
+<
+/
+title
+>
+<
+script
+src
+=
+"
+/
+resources
+/
+testharness
+.
+js
+"
+>
+<
+/
+script
+>
+<
+script
+src
+=
+"
+/
+resources
+/
+testharnessreport
+.
+js
+"
+>
+<
+/
+script
+>
+<
+div
+id
+=
+"
+log
+"
+>
+<
+/
+div
+>
+<
+script
+>
+async_test
+(
+function
+(
+t
+)
+{
+var
+channel
+=
+new
+MessageChannel
+(
+)
+;
+var
+ab
+=
+new
+ArrayBuffer
+(
+1
+)
+;
+channel
+.
+port1
+.
+postMessage
+(
+ab
+{
+transfer
+:
+[
+ab
+]
+}
+)
+;
+channel
+.
+port2
+.
+onmessage
+=
+t
+.
+step_func
+(
+function
+(
+e
+)
+{
+assert_equals
+(
+e
+.
+data
+.
+byteLength
+1
+)
+;
+t
+.
+done
+(
+)
+;
+}
+)
+;
+channel
+.
+port2
+.
+start
+(
+)
+;
+}
+)
+;
+<
+/
+script
+>
diff --git a/testing/web-platform/tests/workers/interfaces/DedicatedWorkerGlobalScope/postMessage/second-argument-dictionary.html b/testing/web-platform/tests/workers/interfaces/DedicatedWorkerGlobalScope/postMessage/second-argument-dictionary.html
new file mode 100644
index 0000000000000..dea4faec27b1b
--- /dev/null
+++ b/testing/web-platform/tests/workers/interfaces/DedicatedWorkerGlobalScope/postMessage/second-argument-dictionary.html
@@ -0,0 +1,216 @@
+<
+!
+-
+-
+onmessage
+=
+(
+event
+)
+=
+>
+{
+try
+{
+postMessage
+(
+event
+.
+data
+{
+transfer
+:
+[
+event
+.
+data
+]
+}
+)
+;
+}
+catch
+(
+e
+)
+{
+postMessage
+(
+'
+'
++
+e
+)
+;
+}
+}
+/
+*
+-
+-
+>
+<
+!
+doctype
+html
+>
+<
+title
+>
+Using
+dictionary
+as
+postMessage
+'
+s
+second
+argument
+<
+/
+title
+>
+<
+script
+src
+=
+"
+/
+resources
+/
+testharness
+.
+js
+"
+>
+<
+/
+script
+>
+<
+script
+src
+=
+"
+/
+resources
+/
+testharnessreport
+.
+js
+"
+>
+<
+/
+script
+>
+<
+div
+id
+=
+"
+log
+"
+>
+<
+/
+div
+>
+<
+script
+>
+(
+async_test
+(
+)
+)
+.
+step
+(
+function
+(
+)
+{
+var
+worker
+=
+new
+Worker
+(
+'
+#
+'
+)
+;
+var
+ab
+=
+new
+ArrayBuffer
+(
+1
+)
+;
+worker
+.
+postMessage
+(
+ab
+{
+transfer
+:
+[
+ab
+]
+}
+)
+;
+worker
+.
+onmessage
+=
+this
+.
+step_func
+(
+function
+(
+e
+)
+{
+assert_equals
+(
+e
+.
+data
+.
+byteLength
+1
+)
+;
+this
+.
+done
+(
+)
+;
+}
+)
+;
+}
+)
+;
+<
+/
+script
+>
+<
+!
+-
+-
+*
+/
+/
+/
+-
+-
+>
diff --git a/testing/web-platform/tests/workers/interfaces/DedicatedWorkerGlobalScope/postMessage/second-argument-null.html b/testing/web-platform/tests/workers/interfaces/DedicatedWorkerGlobalScope/postMessage/second-argument-null.html
index b8e39a588d63f..6c82afb8afe7d 100644
--- a/testing/web-platform/tests/workers/interfaces/DedicatedWorkerGlobalScope/postMessage/second-argument-null.html
+++ b/testing/web-platform/tests/workers/interfaces/DedicatedWorkerGlobalScope/postMessage/second-argument-null.html
@@ -134,8 +134,9 @@
 e
 )
 {
-assert_true
+assert_equals
 (
+1
 e
 .
 data