diff --git a/metadata/extra.go b/metadata/extra.go
index 8389a29..0d5fec5 100644
--- a/metadata/extra.go
+++ b/metadata/extra.go
@@ -1,40 +1,61 @@
 package metadata
 
 import (
+	"encoding/json"
+	"errors"
 	"git.lumeweb.com/LumeWeb/libs5-go/encoding"
 	"git.lumeweb.com/LumeWeb/libs5-go/types"
 	"github.com/vmihailenco/msgpack/v5"
 )
 
+var names = map[types.MetadataExtension]string{
+	types.MetadataExtensionLicenses:           "licenses",
+	types.MetadataExtensionDonationKeys:       "donationKeys",
+	types.MetadataExtensionWikidataClaims:     "wikidataClaims",
+	types.MetadataExtensionLanguages:          "languages",
+	types.MetadataExtensionSourceUris:         "sourceUris",
+	types.MetadataExtensionPreviousVersions:   "previousVersions",
+	types.MetadataExtensionTimestamp:          "timestamp",
+	types.MetadataExtensionOriginalTimestamp:  "originalTimestamp",
+	types.MetadataExtensionTags:               "tags",
+	types.MetadataExtensionCategories:         "categories",
+	types.MetadataExtensionBasicMediaMetadata: "basicMediaMetadata",
+	types.MetadataExtensionViewTypes:          "viewTypes",
+	types.MetadataExtensionBridge:             "bridge",
+	types.MetadataExtensionRoutingHints:       "routingHints",
+}
+
+var namesReverse = map[string]types.MetadataExtension{
+	"licenses":           types.MetadataExtensionLicenses,
+	"donationKeys":       types.MetadataExtensionDonationKeys,
+	"wikidataClaims":     types.MetadataExtensionWikidataClaims,
+	"languages":          types.MetadataExtensionLanguages,
+	"sourceUris":         types.MetadataExtensionSourceUris,
+	"previousVersions":   types.MetadataExtensionPreviousVersions,
+	"timestamp":          types.MetadataExtensionTimestamp,
+	"originalTimestamp":  types.MetadataExtensionOriginalTimestamp,
+	"tags":               types.MetadataExtensionTags,
+	"categories":         types.MetadataExtensionCategories,
+	"basicMediaMetadata": types.MetadataExtensionBasicMediaMetadata,
+	"viewTypes":          types.MetadataExtensionViewTypes,
+	"bridge":             types.MetadataExtensionBridge,
+	"routingHints":       types.MetadataExtensionRoutingHints,
+}
+
 type ExtraMetadata struct {
 	Data map[int]interface{}
 }
 
+var _ SerializableMetadata = (*ExtraMetadata)(nil)
+
 func NewExtraMetadata(data map[int]interface{}) *ExtraMetadata {
 	return &ExtraMetadata{
 		Data: data,
 	}
 }
 
-func (em *ExtraMetadata) ToJSON() map[string]interface{} {
+func (em ExtraMetadata) MarshalJSON() ([]byte, error) {
 	jsonObject := make(map[string]interface{})
-	names := map[types.MetadataExtension]string{
-		types.MetadataExtensionLicenses:           "licenses",
-		types.MetadataExtensionDonationKeys:       "donationKeys",
-		types.MetadataExtensionWikidataClaims:     "wikidataClaims",
-		types.MetadataExtensionLanguages:          "languages",
-		types.MetadataExtensionSourceUris:         "sourceUris",
-		types.MetadataExtensionPreviousVersions:   "previousVersions",
-		types.MetadataExtensionTimestamp:          "timestamp",
-		types.MetadataExtensionOriginalTimestamp:  "originalTimestamp",
-		types.MetadataExtensionTags:               "tags",
-		types.MetadataExtensionCategories:         "categories",
-		types.MetadataExtensionBasicMediaMetadata: "basicMediaMetadata",
-		types.MetadataExtensionViewTypes:          "viewTypes",
-		types.MetadataExtensionBridge:             "bridge",
-		types.MetadataExtensionRoutingHints:       "routingHints",
-	}
-
 	for key, value := range em.Data {
 		name, ok := names[types.MetadataExtension(key)]
 		if ok {
@@ -50,15 +71,43 @@ func (em *ExtraMetadata) ToJSON() map[string]interface{} {
 				} else {
 					jsonObject["updateCID"] = ""
 				}
-
 			} else {
 				jsonObject[name] = value
 			}
 		}
 	}
 
-	return jsonObject
+	return json.Marshal(jsonObject)
 }
+
+func (em *ExtraMetadata) UnmarshalJSON(data []byte) error {
+	// Intermediate representation of the expected JSON structure
+	jsonObject := make(map[string]interface{})
+	if err := json.Unmarshal(data, &jsonObject); err != nil {
+		return err
+	}
+
+	em.Data = make(map[int]interface{})
+	for name, value := range jsonObject {
+		if key, ok := namesReverse[name]; ok {
+			if key == types.MetadataExtensionUpdateCID {
+				// Convert string back to CID bytes
+				cid, err := encoding.Decode(value.(string))
+				if err != nil {
+					return err
+				}
+				em.Data[int(key)] = cid
+			} else {
+				em.Data[int(key)] = value
+			}
+		} else {
+			return errors.New("unknown key in JSON: " + name)
+		}
+	}
+
+	return nil
+}
+
 func (em *ExtraMetadata) DecodeMsgpack(dec *msgpack.Decoder) error {
 	mapLen, err := dec.DecodeMapLen()