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.
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 modular API
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 namespaced API
// 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!
});
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 modular API
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 namespaced API
// 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 modular API
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 namespaced API
// 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.
You can specify custom metadata as an object containing
String
properties.
Web modular API
const metadata = {
customMetadata: {
'location': 'Yosemite, CA, USA',
'activity': 'Hiking'
}
};
Web namespaced API
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.
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.