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After uploading a file toCloud Storagereference, 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 asname,size, andcontentType(often referred to as MIME type) in addition to some less
common ones likecontentDispositionandtimeCreated. This metadata can be
retrieved from aCloud Storagereference using
thegetMetadata()method.getMetadata()returns aPromisecontaining the
complete metadata, or an error if thePromiserejects.
Web
import{getStorage,ref,getMetadata}from"firebase/storage";// Create a reference to the file whose metadata we want to retrieveconststorage=getStorage();constforestRef=ref(storage,'images/forest.jpg');// Get metadata propertiesgetMetadata(forestRef).then((metadata)=>{// Metadata now contains the metadata for 'images/forest.jpg'}).catch((error)=>{// Uh-oh, an error occurred!});
// Create a reference to the file whose metadata we want to retrievevarforestRef=storageRef.child('images/forest.jpg');// Get metadata propertiesforestRef.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 theupdateMetadata()method. Refer to thefull listfor more information on what properties
can be updated. Only the properties specified in the metadata are updated,
all others are left unmodified.updateMetadata()returns aPromisecontaining the complete metadata, or an error if thePromiserejects.
Web
import{getStorage,ref,updateMetadata}from"firebase/storage";// Create a reference to the file whose metadata we want to changeconststorage=getStorage();constforestRef=ref(storage,'images/forest.jpg');// Create file metadata to updateconstnewMetadata={cacheControl:'public,max-age=300',contentType:'image/jpeg'};// Update metadata propertiesupdateMetadata(forestRef,newMetadata).then((metadata)=>{// Updated metadata for 'images/forest.jpg' is returned in the Promise}).catch((error)=>{// Uh-oh, an error occurred!});
// Create a reference to the file whose metadata we want to changevarforestRef=storageRef.child('images/forest.jpg');// Create file metadata to updatevarnewMetadata={cacheControl:'public,max-age=300',contentType:'image/jpeg'};// Update metadata propertiesforestRef.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 tonull:
Web
import{getStorage,ref,updateMetadata}from"firebase/storage";conststorage=getStorage();constforestRef=ref(storage,'images/forest.jpg');// Create file metadata with property to deleteconstdeleteMetadata={contentType:null};// Delete the metadata propertyupdateMetadata(forestRef,deleteMetadata).then((metadata)=>{// metadata.contentType should be null}).catch((error)=>{// Uh-oh, an error occurred!});
// Create file metadata with property to deletevardeleteMetadata={contentType:null};// Delete the metadata propertyforestRef.updateMetadata(deleteMetadata).then((metadata)=>{// metadata.contentType should be null}).catch((error)=>{// Uh-oh, an error occurred!});
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 theHandle Errorssection of the docs.
Custom Metadata
You can specify custom metadata as an object containingStringproperties.
Web
constmetadata={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 theFirebase 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 todelete filesfromCloud Storage.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-09-04 UTC."],[],[],null,["\u003cbr /\u003e\n\nAfter uploading a file to Cloud Storage reference, you can also get\nor update the file metadata, for example to update the content type. Files\ncan also store custom key/value pairs with additional file metadata.\n| **Note:** By default, a Cloud Storage for Firebase bucket requires Firebase Authentication to perform any action on the bucket's data or files. You can change your Firebase Security Rules for Cloud Storage to [allow unauthenticated access for specific situations](/docs/storage/security/rules-conditions#public). However, for most situations, we strongly recommend [restricting access and setting up robust security rules](/docs/storage/security/get-started) (especially for production apps). Note that if you use Google App Engine and have a default Cloud Storage bucket with a name format of `*.appspot.com`, you may need to consider [how your security rules impact access to App Engine files](/docs/storage/gcp-integration#security-rules-and-app-engine-files).\n\nGet File Metadata\n\nFile metadata contains common properties such as `name`, `size`, and\n`contentType` (often referred to as MIME type) in addition to some less\ncommon ones like `contentDisposition` and `timeCreated`. This metadata can be\nretrieved from a Cloud Storage reference using\nthe `getMetadata()` method. `getMetadata()` returns a `Promise` containing the\ncomplete metadata, or an error if the `Promise` rejects. \n\nWeb \n\n```javascript\nimport { getStorage, ref, getMetadata } from \"firebase/storage\";\n\n// Create a reference to the file whose metadata we want to retrieve\nconst storage = getStorage();\nconst forestRef = ref(storage, 'images/forest.jpg');\n\n// Get metadata properties\ngetMetadata(forestRef)\n .then((metadata) =\u003e {\n // Metadata now contains the metadata for 'images/forest.jpg'\n })\n .catch((error) =\u003e {\n // Uh-oh, an error occurred!\n });https://github.com/firebase/snippets-web/blob/467eaa165dcbd9b3ab15711e76fa52237ba37f8b/snippets/storage-next/file-metadata/storage_get_metadata.js#L8-L21\n```\n\nWeb \n\n```javascript\n// Create a reference to the file whose metadata we want to retrieve\nvar forestRef = storageRef.child('images/forest.jpg');\n\n// Get metadata properties\nforestRef.getMetadata()\n .then((metadata) =\u003e {\n // Metadata now contains the metadata for 'images/forest.jpg'\n })\n .catch((error) =\u003e {\n // Uh-oh, an error occurred!\n });https://github.com/firebase/snippets-web/blob/467eaa165dcbd9b3ab15711e76fa52237ba37f8b/storage/file-metadata.js#L8-L18\n```\n\nUpdate File Metadata\n\nYou can update file metadata at any time after the file upload completes by\nusing the `updateMetadata()` method. Refer to the\n[full list](#file_metadata_properties) for more information on what properties\ncan be updated. Only the properties specified in the metadata are updated,\nall others are left unmodified. `updateMetadata()` returns a `Promise`\ncontaining the complete metadata, or an error if the `Promise` rejects. \n\nWeb \n\n```javascript\nimport { getStorage, ref, updateMetadata } from \"firebase/storage\";\n\n// Create a reference to the file whose metadata we want to change\nconst storage = getStorage();\nconst forestRef = ref(storage, 'images/forest.jpg');\n\n// Create file metadata to update\nconst newMetadata = {\n cacheControl: 'public,max-age=300',\n contentType: 'image/jpeg'\n};\n\n// Update metadata properties\nupdateMetadata(forestRef, newMetadata)\n .then((metadata) =\u003e {\n // Updated metadata for 'images/forest.jpg' is returned in the Promise\n }).catch((error) =\u003e {\n // Uh-oh, an error occurred!\n });https://github.com/firebase/snippets-web/blob/467eaa165dcbd9b3ab15711e76fa52237ba37f8b/snippets/storage-next/file-metadata/storage_update_metadata.js#L8-L26\n```\n\nWeb \n\n```javascript\n// Create a reference to the file whose metadata we want to change\nvar forestRef = storageRef.child('images/forest.jpg');\n\n// Create file metadata to update\nvar newMetadata = {\n cacheControl: 'public,max-age=300',\n contentType: 'image/jpeg'\n};\n\n// Update metadata properties\nforestRef.updateMetadata(newMetadata)\n .then((metadata) =\u003e {\n // Updated metadata for 'images/forest.jpg' is returned in the Promise\n }).catch((error) =\u003e {\n // Uh-oh, an error occurred!\n });https://github.com/firebase/snippets-web/blob/467eaa165dcbd9b3ab15711e76fa52237ba37f8b/storage/file-metadata.js#L26-L41\n```\n\nYou can delete a metadata property by setting it to `null`: \n\nWeb \n\n```javascript\nimport { getStorage, ref, updateMetadata } from \"firebase/storage\";\n\nconst storage = getStorage();\nconst forestRef = ref(storage, 'images/forest.jpg');\n\n// Create file metadata with property to delete\nconst deleteMetadata = {\n contentType: null\n};\n\n// Delete the metadata property\nupdateMetadata(forestRef, deleteMetadata)\n .then((metadata) =\u003e {\n // metadata.contentType should be null\n }).catch((error) =\u003e {\n // Uh-oh, an error occurred!\n });https://github.com/firebase/snippets-web/blob/467eaa165dcbd9b3ab15711e76fa52237ba37f8b/snippets/storage-next/file-metadata/storage_delete_metadata.js#L8-L24\n```\n\nWeb \n\n```javascript\n// Create file metadata with property to delete\nvar deleteMetadata = {\n contentType: null\n};\n\n// Delete the metadata property\nforestRef.updateMetadata(deleteMetadata)\n .then((metadata) =\u003e {\n // metadata.contentType should be null\n }).catch((error) =\u003e {\n // Uh-oh, an error occurred!\n });https://github.com/firebase/snippets-web/blob/467eaa165dcbd9b3ab15711e76fa52237ba37f8b/storage/file-metadata.js#L50-L62\n```\n\nHandle Errors\n\nThere are a number of reasons why errors may occur on getting or updating\nmetadata, including the file not existing, or the user not having permission\nto access the desired file. More information on errors can be found in the\n[Handle Errors](/docs/storage/web/handle-errors)\nsection of the docs.\n\nCustom Metadata\n\nYou can specify custom metadata as an object containing `String` properties. \n\nWeb \n\n```javascript\nconst metadata = {\n customMetadata: {\n 'location': 'Yosemite, CA, USA',\n 'activity': 'Hiking'\n }\n};https://github.com/firebase/snippets-web/blob/467eaa165dcbd9b3ab15711e76fa52237ba37f8b/snippets/storage-next/file-metadata/storage_custom_metadata.js#L8-L13\n```\n\nWeb \n\n```javascript\nvar metadata = {\n customMetadata: {\n 'location': 'Yosemite, CA, USA',\n 'activity': 'Hiking'\n }\n};https://github.com/firebase/snippets-web/blob/467eaa165dcbd9b3ab15711e76fa52237ba37f8b/storage/file-metadata.js#L68-L73\n```\n\nYou can use custom metadata for storing additional app specific data for each\nfile, but we highly recommend using a database (such as the\n[Firebase Realtime Database](/docs/database))\nto store and synchronize this type of data.\n\nFile Metadata Properties\n\nA full list of metadata properties on a file is available below:\n\n| Property | Type | Writable |\n|----------------------|--------------------------------------------|-------------------------------------|\n| `bucket` | string | NO |\n| `generation` | string | NO |\n| `metageneration` | string | NO |\n| `fullPath` | string | NO |\n| `name` | string | NO |\n| `size` | number | NO |\n| `timeCreated` | string | NO |\n| `updated` | string | NO |\n| `md5Hash` | string | YES on upload, NO on updateMetadata |\n| `cacheControl` | string | YES |\n| `contentDisposition` | string | YES |\n| `contentEncoding` | string | YES |\n| `contentLanguage` | string | YES |\n| `contentType` | string | YES |\n| `customMetadata` | Object containing string-\\\u003estring mappings | YES |\n\n| **Note:** at present, setting the `md5Hash` property on upload doesn't affect the upload, as hash verification is not yet implemented.\n\nUploading, downloading, and updating files is important, but so is being able\nto remove them. Let's learn how to\n[delete files](/docs/storage/web/delete-files)\nfrom Cloud Storage."]]
