diff --git a/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.cpp b/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.cpp
index bac8f7d65d..e01da0cc6f 100644
--- a/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.cpp
+++ b/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.cpp
@@ -14,6 +14,11 @@ DecoderErrorOr<NonnullOwnPtr<MatroskaDemuxer>> MatroskaDemuxer::from_file(String
     return make<MatroskaDemuxer>(TRY(Reader::from_file(filename)));
 }
 
+DecoderErrorOr<NonnullOwnPtr<MatroskaDemuxer>> MatroskaDemuxer::from_mapped_file(NonnullRefPtr<Core::MappedFile> mapped_file)
+{
+    return make<MatroskaDemuxer>(TRY(Reader::from_mapped_file(move(mapped_file))));
+}
+
 DecoderErrorOr<NonnullOwnPtr<MatroskaDemuxer>> MatroskaDemuxer::from_data(ReadonlyBytes data)
 {
     return make<MatroskaDemuxer>(TRY(Reader::from_data(data)));
diff --git a/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.h b/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.h
index 660175ca2c..eeddd16630 100644
--- a/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.h
+++ b/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.h
@@ -18,6 +18,8 @@ public:
     // FIXME: We should instead accept some abstract data streaming type so that the demuxer
     //        can work with non-contiguous data.
     static DecoderErrorOr<NonnullOwnPtr<MatroskaDemuxer>> from_file(StringView filename);
+    static DecoderErrorOr<NonnullOwnPtr<MatroskaDemuxer>> from_mapped_file(NonnullRefPtr<Core::MappedFile> mapped_file);
+
     static DecoderErrorOr<NonnullOwnPtr<MatroskaDemuxer>> from_data(ReadonlyBytes data);
 
     MatroskaDemuxer(Reader&& reader)
diff --git a/Userland/Libraries/LibVideo/Containers/Matroska/Reader.cpp b/Userland/Libraries/LibVideo/Containers/Matroska/Reader.cpp
index 5b8dd12671..b6a87b194d 100644
--- a/Userland/Libraries/LibVideo/Containers/Matroska/Reader.cpp
+++ b/Userland/Libraries/LibVideo/Containers/Matroska/Reader.cpp
@@ -81,8 +81,13 @@ constexpr u32 CUE_REFERENCE_ID = 0xDB;
 DecoderErrorOr<Reader> Reader::from_file(StringView path)
 {
     auto mapped_file = DECODER_TRY(DecoderErrorCategory::IO, Core::MappedFile::map(path));
+    return from_mapped_file(mapped_file);
+}
+
+DecoderErrorOr<Reader> Reader::from_mapped_file(NonnullRefPtr<Core::MappedFile> mapped_file)
+{
     auto reader = TRY(from_data(mapped_file->bytes()));
-    reader.m_mapped_file = mapped_file;
+    reader.m_mapped_file = move(mapped_file);
     return reader;
 }
 
diff --git a/Userland/Libraries/LibVideo/Containers/Matroska/Reader.h b/Userland/Libraries/LibVideo/Containers/Matroska/Reader.h
index 030ce7ef95..ccfd54ca75 100644
--- a/Userland/Libraries/LibVideo/Containers/Matroska/Reader.h
+++ b/Userland/Libraries/LibVideo/Containers/Matroska/Reader.h
@@ -25,6 +25,8 @@ public:
     typedef Function<DecoderErrorOr<IterationDecision>(TrackEntry const&)> TrackEntryCallback;
 
     static DecoderErrorOr<Reader> from_file(StringView path);
+    static DecoderErrorOr<Reader> from_mapped_file(NonnullRefPtr<Core::MappedFile> mapped_file);
+
     static DecoderErrorOr<Reader> from_data(ReadonlyBytes data);
 
     EBMLHeader const& header() const { return m_header.value(); }
diff --git a/Userland/Libraries/LibVideo/PlaybackManager.cpp b/Userland/Libraries/LibVideo/PlaybackManager.cpp
index 8af53cbce8..7587bf2321 100644
--- a/Userland/Libraries/LibVideo/PlaybackManager.cpp
+++ b/Userland/Libraries/LibVideo/PlaybackManager.cpp
@@ -31,6 +31,12 @@ DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> PlaybackManager::from_file(String
     return create_with_demuxer(move(demuxer));
 }
 
+DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> PlaybackManager::from_mapped_file(NonnullRefPtr<Core::MappedFile> mapped_file)
+{
+    auto demuxer = TRY(Matroska::MatroskaDemuxer::from_mapped_file(move(mapped_file)));
+    return create_with_demuxer(move(demuxer));
+}
+
 DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> PlaybackManager::from_data(ReadonlyBytes data)
 {
     auto demuxer = TRY(Matroska::MatroskaDemuxer::from_data(data));
diff --git a/Userland/Libraries/LibVideo/PlaybackManager.h b/Userland/Libraries/LibVideo/PlaybackManager.h
index 01f55e29e7..60e538212d 100644
--- a/Userland/Libraries/LibVideo/PlaybackManager.h
+++ b/Userland/Libraries/LibVideo/PlaybackManager.h
@@ -101,6 +101,8 @@ public:
     static constexpr SeekMode DEFAULT_SEEK_MODE = SeekMode::Accurate;
 
     static DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> from_file(StringView file);
+    static DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> from_mapped_file(NonnullRefPtr<Core::MappedFile> file);
+
     static DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> from_data(ReadonlyBytes data);
 
     PlaybackManager(NonnullOwnPtr<Demuxer>& demuxer, Track video_track, NonnullOwnPtr<VideoDecoder>&& decoder);