diff --git a/pkg/proto/v0/thumbnails.pb.go b/pkg/proto/v0/thumbnails.pb.go
index 8fb6ad6dac..db7c9109a0 100644
--- a/pkg/proto/v0/thumbnails.pb.go
+++ b/pkg/proto/v0/thumbnails.pb.go
@@ -126,6 +126,7 @@ func (m *GetRequest) GetAuthorization() string {
 
 type GetResponse struct {
 	Thumbnail            []byte   `protobuf:"bytes,1,opt,name=thumbnail,proto3" json:"thumbnail,omitempty"`
+	Mimetype             string   `protobuf:"bytes,2,opt,name=mimetype,proto3" json:"mimetype,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
 	XXX_unrecognized     []byte   `json:"-"`
 	XXX_sizecache        int32    `json:"-"`
@@ -163,6 +164,13 @@ func (m *GetResponse) GetThumbnail() []byte {
 	return nil
 }
 
+func (m *GetResponse) GetMimetype() string {
+	if m != nil {
+		return m.Mimetype
+	}
+	return ""
+}
+
 func init() {
 	proto.RegisterEnum("com.owncloud.ocis.thumbnails.v0.GetRequest_FileType", GetRequest_FileType_name, GetRequest_FileType_value)
 	proto.RegisterType((*GetRequest)(nil), "com.owncloud.ocis.thumbnails.v0.GetRequest")
@@ -172,24 +180,25 @@ func init() {
 func init() { proto.RegisterFile("pkg/proto/v0/thumbnails.proto", fileDescriptor_e354cb4f8a62b6c2) }
 
 var fileDescriptor_e354cb4f8a62b6c2 = []byte{
-	// 300 bytes of a gzipped FileDescriptorProto
+	// 309 bytes of a gzipped FileDescriptorProto
 	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x94, 0x91, 0x4f, 0x4f, 0xc2, 0x40,
-	0x10, 0xc5, 0x2d, 0x50, 0xfe, 0x8c, 0x68, 0xc8, 0xc4, 0x98, 0x86, 0x60, 0x24, 0xc4, 0x03, 0x09,
+	0x10, 0xc5, 0x2d, 0x50, 0xfe, 0x8c, 0x68, 0xc8, 0xc4, 0x98, 0x86, 0x60, 0x24, 0xc4, 0x03, 0x89,
 	0x66, 0x21, 0xe8, 0x27, 0xf0, 0x60, 0x13, 0x0f, 0x86, 0x54, 0x4e, 0xde, 0x4a, 0x19, 0xd9, 0x8d,
-	0xa5, 0xbb, 0xd2, 0x29, 0x04, 0x13, 0x13, 0x3f, 0xba, 0x71, 0x2b, 0x45, 0x4f, 0xea, 0x69, 0xe7,
-	0xfd, 0x76, 0xf2, 0x66, 0xf6, 0x2d, 0x9c, 0x99, 0xe7, 0xc5, 0xd0, 0xac, 0x34, 0xeb, 0xe1, 0x7a,
-	0x34, 0x64, 0x99, 0x2d, 0x67, 0x49, 0xa8, 0xe2, 0x54, 0x58, 0x86, 0xe7, 0x91, 0x5e, 0x0a, 0xbd,
-	0x49, 0xa2, 0x58, 0x67, 0x73, 0xa1, 0x23, 0x95, 0x8a, 0x6f, 0x3d, 0xeb, 0x51, 0xef, 0xbd, 0x04,
-	0xe0, 0x13, 0x07, 0xf4, 0x92, 0x51, 0xca, 0xd8, 0x86, 0xfa, 0x93, 0x8a, 0xc9, 0x84, 0x2c, 0x3d,
-	0xa7, 0xeb, 0xf4, 0x1b, 0x41, 0xa1, 0x71, 0x92, 0xdf, 0xf1, 0xd6, 0x90, 0x57, 0xea, 0x3a, 0xfd,
-	0xe3, 0xf1, 0xb5, 0xf8, 0xc5, 0x5e, 0xec, 0xad, 0xc5, 0xad, 0x8a, 0x69, 0xba, 0x35, 0x14, 0x14,
-	0x2e, 0x88, 0x50, 0x21, 0x0e, 0x17, 0x5e, 0xd9, 0x4e, 0xb2, 0x35, 0x9e, 0x80, 0xbb, 0x51, 0x73,
-	0x96, 0x5e, 0xa5, 0xeb, 0xf4, 0xdd, 0x20, 0x17, 0x78, 0x0a, 0x55, 0x49, 0x6a, 0x21, 0xd9, 0x73,
-	0x2d, 0xfe, 0x52, 0x78, 0x01, 0x47, 0x61, 0xc6, 0x52, 0xaf, 0xd4, 0x6b, 0xc8, 0x4a, 0x27, 0x5e,
-	0xd5, 0x5a, 0xfd, 0x84, 0xbd, 0x0e, 0xd4, 0x77, 0xd3, 0xb1, 0x06, 0xe5, 0xc9, 0xbd, 0xdf, 0x3a,
-	0xf8, 0x2c, 0xee, 0x26, 0x7e, 0xcb, 0xe9, 0x0d, 0xe0, 0xd0, 0xae, 0x99, 0x1a, 0x9d, 0xa4, 0x84,
-	0x1d, 0x68, 0x14, 0x6f, 0xb0, 0x19, 0x34, 0x83, 0x3d, 0x18, 0xbf, 0x41, 0x6b, 0xba, 0x13, 0x0f,
-	0xb4, 0x5a, 0xab, 0x88, 0x50, 0x41, 0xd3, 0x27, 0x2e, 0x30, 0x0e, 0xfe, 0x11, 0x4b, 0xfb, 0xf2,
-	0x6f, 0xcd, 0xf9, 0x72, 0x37, 0xb5, 0x47, 0xd7, 0x7e, 0xec, 0xac, 0x6a, 0x8f, 0xab, 0x8f, 0x00,
-	0x00, 0x00, 0xff, 0xff, 0x54, 0x8e, 0xdc, 0xb1, 0x00, 0x02, 0x00, 0x00,
+	0x6d, 0x77, 0xa5, 0x53, 0x08, 0x26, 0x26, 0x7e, 0x74, 0xc3, 0x22, 0x45, 0x4f, 0xea, 0x69, 0xe7,
+	0xfd, 0x76, 0xf2, 0x66, 0xf6, 0x2d, 0x9c, 0x99, 0x97, 0xf9, 0xc0, 0x2c, 0x34, 0xeb, 0xc1, 0x72,
+	0x38, 0x60, 0x99, 0x27, 0xd3, 0x34, 0x54, 0x71, 0x26, 0x2c, 0xc3, 0xf3, 0x48, 0x27, 0x42, 0xaf,
+	0xd2, 0x28, 0xd6, 0xf9, 0x4c, 0xe8, 0x48, 0x65, 0xe2, 0x5b, 0xcf, 0x72, 0xd8, 0xfb, 0x28, 0x01,
+	0xf8, 0xc4, 0x01, 0xbd, 0xe6, 0x94, 0x31, 0xb6, 0xa1, 0xfe, 0xac, 0x62, 0x32, 0x21, 0x4b, 0xcf,
+	0xe9, 0x3a, 0xfd, 0x46, 0x50, 0x68, 0x1c, 0x6f, 0xef, 0x78, 0x6d, 0xc8, 0x2b, 0x75, 0x9d, 0xfe,
+	0xf1, 0xe8, 0x46, 0xfc, 0x62, 0x2f, 0xf6, 0xd6, 0xe2, 0x4e, 0xc5, 0x34, 0x59, 0x1b, 0x0a, 0x0a,
+	0x17, 0x44, 0xa8, 0x10, 0x87, 0x73, 0xaf, 0x6c, 0x27, 0xd9, 0x1a, 0x4f, 0xc0, 0x5d, 0xa9, 0x19,
+	0x4b, 0xaf, 0xd2, 0x75, 0xfa, 0x6e, 0xb0, 0x15, 0x78, 0x0a, 0x55, 0x49, 0x6a, 0x2e, 0xd9, 0x73,
+	0x2d, 0xfe, 0x52, 0x78, 0x01, 0x47, 0x61, 0xce, 0x52, 0x2f, 0xd4, 0x5b, 0xc8, 0x4a, 0xa7, 0x5e,
+	0xd5, 0x5a, 0xfd, 0x84, 0xbd, 0x0e, 0xd4, 0x77, 0xd3, 0xb1, 0x06, 0xe5, 0xf1, 0x83, 0xdf, 0x3a,
+	0xd8, 0x14, 0xf7, 0x63, 0xbf, 0xe5, 0xf4, 0x7c, 0x38, 0xb4, 0x6b, 0x66, 0x46, 0xa7, 0x19, 0x61,
+	0x07, 0x1a, 0xc5, 0x1b, 0x6c, 0x06, 0xcd, 0x60, 0x0f, 0x36, 0x01, 0x25, 0x2a, 0xd9, 0x87, 0xd0,
+	0x08, 0x0a, 0x3d, 0x7a, 0x87, 0xd6, 0x64, 0xd7, 0xf8, 0x48, 0x8b, 0xa5, 0x8a, 0x08, 0x15, 0x34,
+	0x7d, 0xe2, 0x02, 0xe3, 0xe5, 0x3f, 0x22, 0x6b, 0x5f, 0xfd, 0xad, 0x79, 0xbb, 0xf8, 0x6d, 0xed,
+	0xc9, 0xb5, 0x9f, 0x3e, 0xad, 0xda, 0xe3, 0xfa, 0x33, 0x00, 0x00, 0xff, 0xff, 0xb1, 0x29, 0x25,
+	0xcc, 0x1c, 0x02, 0x00, 0x00,
 }
diff --git a/pkg/proto/v0/thumbnails.proto b/pkg/proto/v0/thumbnails.proto
index 94f2529147..261a65b134 100644
--- a/pkg/proto/v0/thumbnails.proto
+++ b/pkg/proto/v0/thumbnails.proto
@@ -22,4 +22,5 @@ message GetRequest {
 
 message GetResponse {
     bytes thumbnail = 1;
+    string mimetype = 2;
 }
\ No newline at end of file
diff --git a/pkg/service/v0/service.go b/pkg/service/v0/service.go
index b9a6700ac9..3a2f973ace 100644
--- a/pkg/service/v0/service.go
+++ b/pkg/service/v0/service.go
@@ -55,6 +55,7 @@ func (g Thumbnail) GetThumbnail(ctx context.Context, req *v0proto.GetRequest, rs
 	thumbnail := g.manager.GetStored(tCtx)
 	if thumbnail != nil {
 		rsp.Thumbnail = thumbnail
+		rsp.Mimetype = tCtx.Encoder.MimeType()
 		return nil
 	}
 
@@ -74,5 +75,6 @@ func (g Thumbnail) GetThumbnail(ctx context.Context, req *v0proto.GetRequest, rs
 	}
 
 	rsp.Thumbnail = thumbnail
+	rsp.Mimetype = tCtx.Encoder.MimeType()
 	return nil
 }
diff --git a/pkg/thumbnails/encoding.go b/pkg/thumbnails/encoding.go
index 8deb128719..a4d4647bb9 100644
--- a/pkg/thumbnails/encoding.go
+++ b/pkg/thumbnails/encoding.go
@@ -14,6 +14,8 @@ type Encoder interface {
 	Encode(io.Writer, image.Image) error
 	// Types returns the formats suffixes.
 	Types() []string
+	// MimeType returns the mimetype used by the encoder.
+	MimeType() string
 }
 
 // PngEncoder encodes to png
@@ -29,6 +31,11 @@ func (e PngEncoder) Types() []string {
 	return []string{"png"}
 }
 
+// MimeType returns the mimetype for png files.
+func (e PngEncoder) MimeType() string {
+	return "image/png"
+}
+
 // JpegEncoder encodes to jpg.
 type JpegEncoder struct{}
 
@@ -42,6 +49,11 @@ func (e JpegEncoder) Types() []string {
 	return []string{"jpeg", "jpg"}
 }
 
+// MimeType returns the mimetype for jpg files.
+func (e JpegEncoder) MimeType() string {
+	return "image/jpeg"
+}
+
 // EncoderForType returns the encoder for a given file type
 // or nil if the type is not supported.
 func EncoderForType(fileType string) Encoder {