diff --git a/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp b/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp
index b8e605a752e..b4a1250d0fe 100644
--- a/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp
+++ b/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp
@@ -1517,6 +1517,18 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<CryptoKey>> AesCtr::import_key(AlgorithmPar
     return key;
 }
 
+WebIDL::ExceptionOr<JS::Value> AesCtr::get_key_length(AlgorithmParams const& params)
+{
+    // 1. If the length member of normalizedDerivedKeyAlgorithm is not 128, 192 or 256, then throw a OperationError.
+    auto const& normalized_algorithm = static_cast<AesDerivedKeyParams const&>(params);
+    auto length = normalized_algorithm.length;
+    if (length != 128 && length != 192 && length != 256)
+        return WebIDL::OperationError::create(m_realm, "Invalid key length"_string);
+
+    // 2. Return the length member of normalizedDerivedKeyAlgorithm.
+    return JS::Value(length);
+}
+
 // https://w3c.github.io/webcrypto/#hkdf-operations
 WebIDL::ExceptionOr<JS::NonnullGCPtr<CryptoKey>> HKDF::import_key(AlgorithmParams const&, Bindings::KeyFormat format, CryptoKey::InternalKeyData key_data, bool extractable, Vector<Bindings::KeyUsage> const& key_usages)
 {
diff --git a/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.h b/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.h
index be251fb9f19..e1e4a6fa7b9 100644
--- a/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.h
+++ b/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.h
@@ -330,6 +330,7 @@ private:
 class AesCtr : public AlgorithmMethods {
 public:
     virtual WebIDL::ExceptionOr<JS::NonnullGCPtr<CryptoKey>> import_key(AlgorithmParams const&, Bindings::KeyFormat, CryptoKey::InternalKeyData, bool, Vector<Bindings::KeyUsage> const&) override;
+    virtual WebIDL::ExceptionOr<JS::Value> get_key_length(AlgorithmParams const&) override;
 
     static NonnullOwnPtr<AlgorithmMethods> create(JS::Realm& realm) { return adopt_own(*new AesCtr(realm)); }
 
diff --git a/Userland/Libraries/LibWeb/Crypto/SubtleCrypto.cpp b/Userland/Libraries/LibWeb/Crypto/SubtleCrypto.cpp
index 6d25f7d74f4..90b6794b2ec 100644
--- a/Userland/Libraries/LibWeb/Crypto/SubtleCrypto.cpp
+++ b/Userland/Libraries/LibWeb/Crypto/SubtleCrypto.cpp
@@ -778,6 +778,7 @@ SupportedAlgorithmsMap supported_algorithms()
 
     // https://w3c.github.io/webcrypto/#aes-ctr-registration
     define_an_algorithm<AesCtr>("importKey"_string, "AES-CTR"_string);
+    define_an_algorithm<AesCtr, AesDerivedKeyParams>("get key length"_string, "AES-CTR"_string);
 
     // https://w3c.github.io/webcrypto/#hkdf
     define_an_algorithm<HKDF>("importKey"_string, "HKDF"_string);