After uploading a file to Cloud Storage reference, you can also get or update the file metadata, for example to 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 as name
, size
, and
contentType
(often referred to as MIME type) in addition to some less
common ones like contentDisposition
and timeCreated
. This metadata can be
retrieved from a Cloud Storage reference using
the getMetadata()
method. getMetadata()
returns a Promise
containing the
complete metadata, or an error if the Promise
rejects.
Web
import { getStorage, ref, getMetadata } from "firebase/storage"; // Create a reference to the file whose metadata we want to retrieve const storage = getStorage(); const forestRef = ref(storage, 'images/forest.jpg'); // Get metadata properties getMetadata(forestRef) .then((metadata) => { // Metadata now contains the metadata for 'images/forest.jpg' }) .catch((error) => { // Uh-oh, an error occurred! });
Web
// Create a reference to the file whose metadata we want to retrieve var forestRef = storageRef.child('images/forest.jpg'); // Get metadata properties forestRef.getMetadata() .then((metadata) => { // Metadata now contains the metadata for 'images/forest.jpg' }) .catch((error) => { // Uh-oh, an error occurred! });
Update File Metadata
You can update file metadata at any time after the file upload completes by
using the updateMetadata()
method. Refer to the
full list for more information on what properties
can be updated. Only the properties specified in the metadata are updated,
all others are left unmodified. updateMetadata()
returns a Promise
containing the complete metadata, or an error if the Promise
rejects.
Web
import { getStorage, ref, updateMetadata } from "firebase/storage"; // Create a reference to the file whose metadata we want to change const storage = getStorage(); const forestRef = ref(storage, 'images/forest.jpg'); // Create file metadata to update const newMetadata = { cacheControl: 'public,max-age=300', contentType: 'image/jpeg' }; // Update metadata properties updateMetadata(forestRef, newMetadata) .then((metadata) => { // Updated metadata for 'images/forest.jpg' is returned in the Promise }).catch((error) => { // Uh-oh, an error occurred! });
Web
// Create a reference to the file whose metadata we want to change var forestRef = storageRef.child('images/forest.jpg'); // Create file metadata to update var newMetadata = { cacheControl: 'public,max-age=300', contentType: 'image/jpeg' }; // Update metadata properties forestRef.updateMetadata(newMetadata) .then((metadata) => { // Updated metadata for 'images/forest.jpg' is returned in the Promise }).catch((error) => { // Uh-oh, an error occurred! });
You can delete a metadata property by setting it to null
:
Web
import { getStorage, ref, updateMetadata } from "firebase/storage"; const storage = getStorage(); const forestRef = ref(storage, 'images/forest.jpg'); // Create file metadata with property to delete const deleteMetadata = { contentType: null }; // Delete the metadata property updateMetadata(forestRef, deleteMetadata) .then((metadata) => { // metadata.contentType should be null }).catch((error) => { // Uh-oh, an error occurred! });
Web
// Create file metadata with property to delete var deleteMetadata = { contentType: null }; // Delete the metadata property forestRef.updateMetadata(deleteMetadata) .then((metadata) => { // metadata.contentType should be null }).catch((error) => { // Uh-oh, an error occurred! });
Handle Errors
There are a number of reasons why errors may occur on getting or updating metadata, including the file not existing, or the user not having permission to access the desired file. More information on errors can be found in the Handle Errors section of the docs.
Custom Metadata
You can specify custom metadata as an object containing String
properties.
Web
const metadata = { customMetadata: { 'location': 'Yosemite, CA, USA', 'activity': 'Hiking' } };
Web
var metadata = { customMetadata: { 'location': 'Yosemite, CA, USA', 'activity': 'Hiking' } };
You can use custom metadata for storing additional app specific data for each file, but we highly recommend using a database (such as the Firebase Realtime Database) to store and synchronize this type of data.
File Metadata Properties
A full list of metadata properties on a file is available below:
Property | Type | Writable |
---|---|---|
bucket |
string | NO |
generation |
string | NO |
metageneration |
string | NO |
fullPath |
string | NO |
name |
string | NO |
size |
number | NO |
timeCreated |
string | NO |
updated |
string | NO |
md5Hash |
string | YES on upload, NO on updateMetadata |
cacheControl |
string | YES |
contentDisposition |
string | YES |
contentEncoding |
string | YES |
contentLanguage |
string | YES |
contentType |
string | YES |
customMetadata |
Object containing string->string mappings | YES |
Uploading, downloading, and updating files is important, but so is being able to remove them. Let's learn how to delete files from Cloud Storage.