After uploading a file toCloud Storage reference, you can also getand update the file metadata, for example to update the content type. Filescan also store custom key/value pairs with additional file metadata.

Get File Metadata

File metadata contains common properties such asName,SizeBytes, andContentType (often referred to as MIME type) in addition to someless common ones likeContentDisposition andCreationTimeMillis. Thismetadata can be retrieved from aCloud Storage reference using theGetMetadataAsync method.

// Create reference to the file whose metadata we want to retrieveStorageReferenceforestRef=storageRef.Child("images/forest.jpg");// Get metadata propertiesforestRef.GetMetadataAsync().ContinueWithOnMainThread(task=>{if(!task.IsFaulted &&!task.IsCanceled){StorageMetadatameta=task.Result;// do stuff with meta}});

Update File Metadata

You can update file metadata at any time after the file upload completes byusing theUpdateMetadataAsync method which takes aMetadataChange object.Refer to thefull list for more information on whatproperties can be updated. Only the properties specified in the metadata areupdated, all others are left unmodified.

// Create reference to the file whose metadata we want to changeStorageReferenceforestRef=storageRef.Child("images/forest.jpg");// Create file metadata to updatevarnewMetadata=newMetadataChange();newMetadata.CacheControl="public,max-age=300";newMetadata.ContentType="image/jpeg";// Update metadata propertiesforestRef.UpdateMetadataAsync(newMetadata).ContinueWithOnMainThread(task=>{if(!task.IsFaulted &&!task.IsCanceled){// access the updated meta dataStorageMetadatameta=task.Result;}});

You can delete writable metadata properties by passing the empty string:

// Create file metadata to updatevarnewMetadata=newMetadataChange();newMetadata.ContentType="";// Update metadata propertiesforestRef.UpdateMetadataAsync(newMetadata).ContinueWithOnMainThread(task=>{if(!task.IsFaulted &&!task.IsCanceled){StorageMetadatameta=task.Result;// meta.ContentType should be an empty string now}});

Handle Errors

There are a number of reasons why errors may occur on getting or updatingmetadata, including the file not existing, or the user not having permissionto access the desired file. More information on errors can be found in theHandle Errorssection of the docs.

Custom Metadata

You can specify custom metadata as aDictionary<string, string>.

varnewMetadata=newMetadataChange{CustomMetadata=newDictionary<string,string>{{"location","Yosemite, CA, USA"},{"activity","Hiking"}}};// UpdateMetadataAsync

You can store app-specific data for each file in custom metadata, but we highlyrecommend using a database (such as theFirebase Realtime Database) to store and synchronize this type ofdata.

File Metadata Properties

A full list of metadata properties on a file is available below:

Next Steps

Uploading, downloading, and updating files is important, but so is being ableto remove them. Let's learn how todelete filesfromCloud Storage.