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

Get File Metadata

File metadata contains common properties such asname,size, andcontentType (often referred to as MIME type) in addition to some lesscommon ones likecontentDisposition andtimeCreated. This metadata can beretrieved from a Cloud Storage reference usingthegetMetadata() method.

// Create reference to the file whose metadata we want to retrievefinalforestRef=storageRef.child("images/forest.jpg");// Get metadata propertiesfinalmetadata=awaitforestRef.getMetadata();// Metadata now contains the metadata for 'images/forest.jpg'

Update File Metadata

You can update file metadata at any time after the file upload completes byusing theupdateMetadata() method. Refer to thefull list for more information on what propertiescan be updated. Only the properties specified in the metadata are updated,all others are left unmodified.

// Create reference to the file whose metadata we want to changefinalforestRef=storageRef.child("images/forest.jpg");// Create file metadata to updatefinalnewMetadata=SettableMetadata(cacheControl:"public,max-age=300",contentType:"image/jpeg",);// Update metadata propertiesfinalmetadata=awaitforestRef.updateMetadata(newMetadata);// Updated metadata for 'images/forest.jpg' is returned

You can delete writable metadata properties by passingnull:

// Delete the cacheControl propertyfinalnewMetadata=SettableMetadata(cacheControl:null);finalmetadata=awaitforestRef.updateMetadata(newMetadata);

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 Errors section of the docs.

Custom Metadata

You can specify custom metadata using thecustomMetadata parameter of theSettableMetadata constructor:

// Create reference to the file whose metadata we want to changefinalforestRef=storageRef.child("images/forest.jpg");// Create file metadata to updatefinalnewCustomMetadata=SettableMetadata(customMetadata:{"location":"Yosemite, CA, USA","activity":"Hiking",},);// Update metadata propertiesfinalmetadata=awaitforestRef.updateMetadata(newCustomMetadata);// Updated metadata for 'images/forest.jpg' is returned

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:

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