Notice: Over the next few months, we're reorganizing the App Engine documentation site to make it easier to find content and better align with the rest of Google Cloud products. The same content will be available, but the navigation will now match the rest of the Cloud products. If you have feedback or questions as you navigate the site, click Send Feedback.

Use Cloud Storage

You can use Cloud Storage to store and serve files, such as movies or images or other static content.

This document describes how to use the Cloud Client Libraries for Cloud Storage in your app to store data and retrieve data from Cloud Storage from Cloud Storage.

Before you begin

  • Follow the instructions in Setting up your development environment to set up your environment and project, and to understand how apps are structured in App Engine. Write down and save your project ID, because you will need it to run the sample application described in this document.

  • Make sure you create a Cloud Storage bucket for your application by invoking the following command:

    gsutil mb gs://[YOUR_BUCKET_NAME]

  • Make the bucket publicly readable so it can serve files:

    gsutil defacl set public-read gs://[YOUR_BUCKET_NAME]

Download the sample

Go

To clone the repository:

v1.18 and later 

  git clone https://github.com/GoogleCloudPlatform/golang-samples.git
  cd golang-samples/appengine_flexible/storage

v1.15 and earlier 

  git clone https://github.com/GoogleCloudPlatform/golang-samples.git
  cd golang-samples/appengine_flexible/go115_and_earlier/storage

Java

To clone the repository:

version 11/17 

  git clone https://github.com/GoogleCloudPlatform/java-docs-samples
  cd java-docs-samples/flexible/java-11/cloudstorage

version 8 

  git clone https://github.com/GoogleCloudPlatform/java-docs-samples
  cd java-docs-samples/flexible/java-8/cloudstorage

Node.js

To clone the repository:

v18 and later 

  git clone https://github.com/GoogleCloudPlatform/nodejs-docs-samples/
  cd nodejs-docs-samples/appengine/storage/flexible

v16 and earlier 

  git clone https://github.com/GoogleCloudPlatform/nodejs-docs-samples/
  cd nodejs-docs-samples/appengine/storage/flexible_nodejs16_and_earlier

PHP

To clone the repository:

git clone https://github.com/GoogleCloudPlatform/php-docs-samples
cd php-docs-samples/appengine/flexible/storage

Python

To clone the repository:

v3.8 and later 

git clone https://github.com/GoogleCloudPlatform/python-docs-samples
cd python-docs-samples/appengine/flexible/storage

v3.7 and earlier 

git clone https://github.com/GoogleCloudPlatform/python-docs-samples
cd python-docs-samples/appengine/flexible_python37_and_earlier/storage

Ruby

To clone the repository:

version 3.2 

git clone https://github.com/GoogleCloudPlatform/ruby-docs-samples
cd ruby-docs-samples/appengine/flexible/storage/

version 3.1 and earlier 

git clone https://github.com/GoogleCloudPlatform/ruby-docs-samples
cd ruby-docs-samples/appengine/flexible/ruby31-and-earlier/storage/

.NET

  1. Download the sample app and extract it.

  2. If you're using the command line, navigate into the app directory, dotnet-docs-samples\appengine\flexible\` on branchflex-dotnet3-and-earlier`.

To run your application locally, set up a service account and download credentials:

  1. Open the list of credentials in the Google Cloud console.

    Open the list of credentials

  2. Click Create credentials.

  3. Select Service account key.

    A Create service account key window opens.

  4. Click the drop-down box below Service account, then click Compute Engine default service account.

  5. Select JSON for the Key type.

  6. Click Create.

    A New private key window is displayed and the private key for the is downloaded automatically.

  7. Click Close.

  8. Set the environment variable GOOGLE_APPLICATION_CREDENTIALS to the path of the JSON key that was downloaded. For example, in PowerShell:

    # For this powershell session.
PS > $env:GOOGLE_APPLICATION_CREDENTIALS = "$env:USERPROFILE\Downloads\your-project-id-dea9fa230eae3.json"
# For all processes created after this command.
PS > [Environment]::SetEnvironmentVariable("GOOGLE_APPLICATION_CREDENTIALS", "$env:USERPROFILE\Downloads\your-project-id-dea9fa230eae3.json", "User")

Edit project configuration and install dependencies

Go

In app.yaml, set GCLOUD_STORAGE_BUCKET. This value is the name of the Cloud Storage bucket you created previously.

v1.18 and later

appengine_flexible/storage/app.yaml 
# Copyright 2019 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

runtime: go
env: flex

runtime_config:
  operating_system: ubuntu22
  runtime_version: 1.19

automatic_scaling:
  min_num_instances: 1

env_variables:
  GCLOUD_STORAGE_BUCKET: your-bucket-name

v1.15 and earlier

appengine_flexible/go115_and_earlier/storage/app.yaml 
# Copyright 2023 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

runtime: go
env: flex

automatic_scaling:
  min_num_instances: 1

env_variables:
  GCLOUD_STORAGE_BUCKET: your-bucket-name

Java

In app.yaml, set the BUCKET_NAME to the Cloud Storage you previously created for your project.

version 11/17

flexible/java-11/cloudstorage/src/main/appengine/app.yaml 
runtime: java
env: flex
runtime_config:
  operating_system: ubuntu18
  runtime_version: 11
handlers:
- url: /.*
  script: this field is required, but ignored

env_variables:
  BUCKET_NAME: YOUR-BUCKET-NAME

version 8

flexible/java-8/cloudstorage/src/main/appengine/app.yaml 
#  Copyright 2023 Google Inc.
#
#  Licensed under the Apache License, Version 2.0 (the "License");
#  you may not use this file except in compliance with the License.
#  You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS,
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#  See the License for the specific language governing permissions and
#  limitations under the License.

runtime: java
env: flex

handlers:
- url: /.*
  script: this field is required, but ignored

env_variables:
  BUCKET_NAME: YOUR-BUCKET-NAME

In pom.xml, set com.google.cloud as a dependency, and specify google-cloud-storage as the artifactID for that dependency; this provides the functions to use Cloud Storage.

version 11/17

flexible/java-11/cloudstorage/pom.xml 
<!--  Using libraries-bom to manage versions.
See https://github.com/GoogleCloudPlatform/cloud-opensource-java/wiki/The-Google-Cloud-Platform-Libraries-BOM -->
<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.google.cloud</groupId>
      <artifactId>libraries-bom</artifactId>
      <version>26.12.0</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-dependencies</artifactId>
      <version>${spring.boot.version}</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>

<dependencies>
  <dependency>
    <groupId>com.google.cloud</groupId>
    <artifactId>google-cloud-storage</artifactId>
  </dependency>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
  </dependency>
  <dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>4.0.1</version>
    <type>jar</type>
    <scope>provided</scope>
  </dependency>
  <dependency>
    <groupId>org.junit.vintage</groupId>
    <artifactId>junit-vintage-engine</artifactId>
    <scope>test</scope>
  </dependency>
  <dependency>
    <groupId>org.junit-pioneer</groupId>
    <artifactId>junit-pioneer</artifactId>
    <version>2.0.1</version>
    <scope>test</scope>
  </dependency>
  <dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-inline</artifactId>
    <version>5.2.0</version>
    <scope>test</scope>
  </dependency>
  <dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-junit-jupiter</artifactId>
    <version>5.3.1</version>
    <scope>test</scope>
  </dependency>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
  </dependency>

</dependencies>

version 8

flexible/java-8/cloudstorage/pom.xml 
<!--  Using libraries-bom to manage versions.
See https://github.com/GoogleCloudPlatform/cloud-opensource-java/wiki/The-Google-Cloud-Platform-Libraries-BOM -->
<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.google.cloud</groupId>
      <artifactId>libraries-bom</artifactId>
      <version>26.12.0</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>

<dependencies>
  <dependency>
    <groupId>com.google.cloud</groupId>
    <artifactId>google-cloud-storage</artifactId>
  </dependency>
</dependencies>

Node.js

In app.yaml, add your project ID to the GOOGLE_CLOUD_PROJECT environment value. Then set the GCLOUD_STORAGE_BUCKET environment value to the name of the Cloud Storage bucket you created previously.

v18 and later

appengine/storage/flexible/app.yaml 
runtime: nodejs
env: flex
runtime_config:
  operating_system: ubuntu22

env_variables:
  GCLOUD_STORAGE_BUCKET: YOUR_BUCKET_NAME

v16 and earlier

appengine/storage/flexible_nodejs16_and_earlier/app.yaml 
runtime: nodejs
env: flex

env_variables:
  GCLOUD_STORAGE_BUCKET: YOUR_BUCKET_NAME

In package.json, add @google-cloud/storage as a dependency, which provides the functions to use Cloud Storage.

v18 and later

appengine/storage/flexible/package.json 
{
  "name": "appengine-storage",
  "description": "Node.js Google Cloud Storage sample for Google App Engine",
  "scripts": {
    "start": "node app.js",
    "test": "c8 mocha system-test/*.test.js --exit --timeout=30000"
  },
  "engines": {
    "node": ">=18.x.x"
  },
  "dependencies": {
    "@google-cloud/storage": "^6.9.3",
    "express": "^4.18.2",
    "multer": "^1.4.5-lts.1",
    "pug": "^3.0.2"
  },
  "devDependencies": {
    "@types/express": "^4.17.17",
    "@types/multer": "^1.4.7",
    "@types/proxyquire": "^1.3.28",
    "@types/supertest": "^2.0.12",
    "@types/uuid": "^9.0.1",
    "c8": "^7.13.0",
    "mocha": "^10.2.0",
    "proxyquire": "^2.1.3",
    "supertest": "^6.3.3",
    "uuid": "^9.0.0"
  }
}

v16 and earlier

appengine/storage/flexible_nodejs16_and_earlier/package.json 
{
  "name": "appengine-storage",
  "description": "Node.js Google Cloud Storage sample for Google App Engine",
  "scripts": {
    "start": "node app.js",
    "test": "c8 mocha system-test/*.test.js --exit --timeout=30000"
  },
  "engines": {
    "node": "16.x.x"
  },
  "dependencies": {
    "@google-cloud/storage": "^6.9.3",
    "express": "^4.18.2",
    "multer": "^1.4.5-lts.1",
    "pug": "^3.0.2"
  },
  "devDependencies": {
    "@types/express": "^4.17.17",
    "@types/multer": "^1.4.7",
    "@types/proxyquire": "^1.3.28",
    "@types/supertest": "^2.0.12",
    "@types/uuid": "^9.0.1",
    "c8": "^7.13.0",
    "mocha": "^10.2.0",
    "proxyquire": "^2.1.3",
    "supertest": "^6.3.3",
    "uuid": "^9.0.0"
  }
}

See the README.md file for instructions on running and testing locally.

PHP

In app.yaml, set CLOUD_STORAGE_BUCKET; this value is the name of the Cloud Storage bucket you created previously.

appengine/flexible/storage/app.yaml 
env_variables:
  GOOGLE_STORAGE_BUCKET: "your-bucket-name"

In composer.json, notice that you must include the Cloud Client library, because this provides Cloud Storage functions.

appengine/flexible/storage/composer.json 
{
    "require": {
        "slim/slim": "^4.0",
        "slim/psr7": "^1.3",
        "google/cloud-storage": "^1.0",
        "php-di/slim-bridge": "^3.1"
    }
}

Python

In app.yaml, set GOOGLE_STORAGE_BUCKET; this value is the name of the Cloud Storage bucket you created previously.

v3.8 and later

appengine/flexible/storage/app.yaml 
env_variables:
  CLOUD_STORAGE_BUCKET: [your-bucket-name]

v3.7 and earlier

appengine/flexible_python37_and_earlier/storage/app.yaml 
env_variables:
    CLOUD_STORAGE_BUCKET: your-bucket-name

In requirements.txt, notice that you must include the google-cloud-storage library, because this provides Cloud Storage functions.

v3.8 and later

appengine/flexible/storage/requirements.txt 
Flask==2.1.0
werkzeug==2.2.3
google-cloud-storage==2.8.0
gunicorn==20.1.0

v3.7 and earlier

appengine/flexible_python37_and_earlier/storage/requirements.txt 
Flask==2.1.0; python_version > '3.6'
Flask==2.0.3; python_version < '3.7'
werkzeug==2.2.3; python_version > '3.6'
werkzeug==2.0.3; python_version < '3.7'
google-cloud-storage==2.8.0
gunicorn==20.1.0

Ruby

In app.yaml, set the GCLOUD_STORAGE_BUCKET to the Cloud Storage you previously created for your project.

version 3.2

appengine/flexible/storage/app.yaml 
runtime: ruby
env: flex
entrypoint: bundle exec ruby app.rb

runtime_config:
  operating_system: ubuntu22

env_variables:
  GOOGLE_CLOUD_STORAGE_BUCKET: <your-bucket-name>

version 3.1 and earlier

appengine/flexible/ruby31-and-earlier/storage/app.yaml 
runtime: ruby
env: flex
entrypoint: bundle exec ruby app.rb

env_variables:
  GOOGLE_CLOUD_STORAGE_BUCKET: <your-bucket-name>

Note that you must include the gcloud library in Gemfile to use Cloud Storage functions.

source "https://rubygems.org"

gem "google-cloud-storage"
gem "sinatra"

.NET

In appsettings.json, set BucketName; this value is the name of the Cloud Storage bucket you created previously.

appengine/flexible/CloudStorage/appsettings.json 
{
  "GoogleCloudStorage": {
    "BucketName": "your-google-bucket-name"
  },
  "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
    }
  }
}

Application code

Go

The sample application presents a web page prompting the user to supply a file to be stored in Cloud Storage. When the user selects a file and clicks submit, the upload handler writes the file to the Cloud Storage bucket using Cloud Storage NewWriter function.

Notice that to retrieve this file from Cloud Storage, you will need to specify the bucket name and the filename. You should store these values in your app for future use.

// Copyright 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.


// Sample storage demonstrates use of the cloud.google.com/go/storage package from App Engine flexible environment.
package main

import (
	"context"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"os"

	"cloud.google.com/go/storage"
	"google.golang.org/appengine"
)

var (
	storageClient *storage.Client

	// Set this in app.yaml when running in production.
	bucket = os.Getenv("GCLOUD_STORAGE_BUCKET")
)

func main() {
	ctx := context.Background()

	var err error
	storageClient, err = storage.NewClient(ctx)
	if err != nil {
		log.Fatal(err)
	}

	http.HandleFunc("/", formHandler)
	http.HandleFunc("/upload", uploadHandler)

	appengine.Main()
}

func uploadHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		http.Error(w, "", http.StatusMethodNotAllowed)
		return
	}

	ctx := appengine.NewContext(r)

	f, fh, err := r.FormFile("file")
	if err != nil {
		msg := fmt.Sprintf("Could not get file: %v", err)
		http.Error(w, msg, http.StatusBadRequest)
		return
	}
	defer f.Close()

	sw := storageClient.Bucket(bucket).Object(fh.Filename).NewWriter(ctx)
	if _, err := io.Copy(sw, f); err != nil {
		msg := fmt.Sprintf("Could not write file: %v", err)
		http.Error(w, msg, http.StatusInternalServerError)
		return
	}

	if err := sw.Close(); err != nil {
		msg := fmt.Sprintf("Could not put file: %v", err)
		http.Error(w, msg, http.StatusInternalServerError)
		return
	}

	u, _ := url.Parse("/" + bucket + "/" + sw.Attrs().Name)

	fmt.Fprintf(w, "Successful! URL: https://storage.googleapis.com%s", u.EscapedPath())
}

func formHandler(w http.ResponseWriter, r *http.Request) {
	fmt.Fprint(w, formHTML)
}

const formHTML = `<!DOCTYPE html>
<html>
  <head>
    <title>Storage</title>
    <meta charset="utf-8">
  </head>
  <body>
    <form method="POST" action="/upload" enctype="multipart/form-data">
      <input type="file" name="file">
      <input type="submit">
    </form>
  </body>
</html>`

Java

The sample application presents a web page prompting the user to supply a file to be stored in Cloud Storage. When the user selects a file and clicks submit, the doPost request handler writes the file to the Cloud Storage bucket using Storage.create

Notice that to retrieve this file from Cloud Storage, you will need to specify the bucket name and the filename. You should store these values in your app for future use.

version 11/17

flexible/java-11/cloudstorage/src/main/java/com/example/cloudstorage/UploadServlet.java 
@SuppressWarnings("serial")
@WebServlet(name = "upload", value = "/upload")
@MultipartConfig()
public class UploadServlet extends HttpServlet {

  private static final String BUCKET_NAME =
      System.getenv().getOrDefault("BUCKET_NAME", "my-test-bucket");
  private static Storage storage = null;

  public UploadServlet() {
    storage = StorageOptions.getDefaultInstance().getService();
  }

  @Override
  public void doPost(HttpServletRequest req, HttpServletResponse resp)
      throws IOException, ServletException {
    final Part filePart = req.getPart("file");
    final String fileName = filePart.getSubmittedFileName();
    // Modify access list to allow all users with link to read file
    List<Acl> acls = new ArrayList<>();
    acls.add(Acl.of(Acl.User.ofAllUsers(), Acl.Role.READER));
    // the inputstream is closed by default, so we don't need to close it here
    Blob blob =
        storage.create(
            BlobInfo.newBuilder(BUCKET_NAME, fileName).setAcl(acls).build(),
            filePart.getInputStream());

    // return the public download link
    resp.getWriter().print(blob.getMediaLink());
  }
}

version 8

flexible/java-8/cloudstorage/src/main/java/com/example/cloudstorage/UploadServlet.java 
@SuppressWarnings("serial")
@WebServlet(name = "upload", value = "/upload")
@MultipartConfig()
public class UploadServlet extends HttpServlet {

  private static final String BUCKET_NAME = System.getenv("BUCKET_NAME");
  private static Storage storage = null;

  @Override
  public void init() {
    storage = StorageOptions.getDefaultInstance().getService();
  }

  @Override
  public void doPost(HttpServletRequest req, HttpServletResponse resp)
      throws IOException, ServletException {
    final Part filePart = req.getPart("file");
    final String fileName = filePart.getSubmittedFileName();

    // Modify access list to allow all users with link to read file
    List<Acl> acls = new ArrayList<>();
    acls.add(Acl.of(Acl.User.ofAllUsers(), Acl.Role.READER));
    // the inputstream is closed by default, so we don't need to close it here
    Blob blob =
        storage.create(
            BlobInfo.newBuilder(BUCKET_NAME, fileName).setAcl(acls).build(),
            filePart.getInputStream());

    // return the public download link
    resp.getWriter().print(blob.getMediaLink());
  }
}

Node.js

The sample application presents a web page prompting the user to supply a file to be stored in Cloud Storage. When the user selects a file and clicks submit, the upload handler loads the file content into a blob and writes it to Cloud Storage.

Notice that after the file is uploaded to Cloud Storage, the public URL to this file is returned, which you can use to serve the file directly from Cloud Storage. You should store this value in your app for future use.

const {format} = require('util');
const express = require('express');
const Multer = require('multer');

// By default, the client will authenticate using the service account file
// specified by the GOOGLE_APPLICATION_CREDENTIALS environment variable and use
// the project specified by the GOOGLE_CLOUD_PROJECT environment variable. See
// https://github.com/GoogleCloudPlatform/google-cloud-node/blob/master/docs/authentication.md
// These environment variables are set automatically on Google App Engine
const {Storage} = require('@google-cloud/storage');

// Instantiate a storage client
const storage = new Storage();

const app = express();
app.set('view engine', 'pug');

// This middleware is available in Express v4.16.0 onwards
app.use(express.json());

// Multer is required to process file uploads and make them available via
// req.files.
const multer = Multer({
  storage: Multer.memoryStorage(),
  limits: {
    fileSize: 5 * 1024 * 1024, // no larger than 5mb, you can change as needed.
  },
});

// A bucket is a container for objects (files).
const bucket = storage.bucket(process.env.GCLOUD_STORAGE_BUCKET);

// Display a form for uploading files.
app.get('/', (req, res) => {
  res.render('form.pug');
});

// Process the file upload and upload to Google Cloud Storage.
app.post('/upload', multer.single('file'), (req, res, next) => {
  if (!req.file) {
    res.status(400).send('No file uploaded.');
    return;
  }

  // Create a new blob in the bucket and upload the file data.
  const blob = bucket.file(req.file.originalname);
  const blobStream = blob.createWriteStream();

  blobStream.on('error', err => {
    next(err);
  });

  blobStream.on('finish', () => {
    // The public URL can be used to directly access the file via HTTP.
    const publicUrl = format(
      `https://storage.googleapis.com/${bucket.name}/${blob.name}`
    );
    res.status(200).send(publicUrl);
  });

  blobStream.end(req.file.buffer);
});

const PORT = parseInt(process.env.PORT) || 8080;
app.listen(PORT, () => {
  console.log(`App listening on port ${PORT}`);
  console.log('Press Ctrl+C to quit.');
});

PHP

The sample application presents a web page prompting the user to supply a file to be stored in Cloud Storage. When the user selects a file and clicks submit, the upload handler loads the file content into a blob and writes it to Cloud Storage.

Notice that after the file is uploaded to Cloud Storage, the public URL to this file is returned, which you can use to serve the file directly from Cloud Storage. You should store this value in your app for future use.

appengine/flexible/storage/app.php 
use DI\Container;
use Google\Cloud\Storage\StorageClient;
use Psr\Http\Message\ServerRequestInterface as Request;
use Psr\Http\Message\ResponseInterface as Response;
use Slim\Factory\AppFactory;

// Create App
AppFactory::setContainer($container = new Container());
$app = AppFactory::create();

// Display errors
$app->addErrorMiddleware(true, true, true);

$container = $app->getContainer();

$app->get('/', function (Request $request, Response $response) use ($container) {
    /** @var Google\Cloud\StorageClient */
    $storage = $container->get('storage');
    $bucketName = $container->get('bucket_name');
    $objectName = $container->get('object_name');
    $bucket = $storage->bucket($bucketName);
    $object = $bucket->object($objectName);
    $content = $object->exists() ? $object->downloadAsString() : '';
    $escapedContent = htmlspecialchars($content);
    $response->getBody()->write(<<<EOF
    <h1>Storage Example</h1>
    <h3>Write [<a href="https://cloud.google.com/appengine/docs/flexible/php/using-cloud-storage">docs</a>]:</h3>
    <form action="/write" method="post">
        Some file content:<br />
        <textarea name="content"></textarea><br />
        <input type="submit" />
    </form>
EOF
    );
    if ($content) {
        $response->getBody()->write(
            "<p><strong>Your content:</strong><p><p>$escapedContent</p>"
        );
    }
    return $response;
});

/**
 * Write to a Storage bucket.
 * @see https://cloud.google.com/appengine/docs/flexible/php/using-cloud-storage
 */
$app->post('/write', function (Request $request, Response $response) use ($container) {
    /** @var Google\Cloud\StorageClient */
    $storage = $container->get('storage');
    $bucketName = $container->get('bucket_name');
    $objectName = $container->get('object_name');
    parse_str((string) $request->getBody(), $postData);
    $metadata = ['contentType' => 'text/plain'];
    $storage->bucket($bucketName)->upload($postData['content'] ?? '', [
        'name' => $objectName,
        'metadata' => $metadata,
    ]);
    return $response
        ->withStatus(302)
        ->withHeader('Location', '/');
});

$container->set('storage', function () use ($container) {
    $projectId = $container->get('project_id');
    $storage = new StorageClient([
        'projectId' => $projectId
    ]);
    return $storage;
});

Python

The sample application presents a web page prompting the user to supply a file to be stored in Cloud Storage. When the user selects a file and clicks submit, the upload handler loads the file content into a Cloud Storage blob and writes it to the Cloud Storage bucket.

Notice that after the file is uploaded to Cloud Storage, the public URL to this file is returned, which you can use to serve the file directly from Cloud Storage. You should store this value in your app for future use.

v3.8 and later

appengine/flexible/storage/main.py 
from __future__ import annotations

import logging
import os

from flask import Flask, request
from google.cloud import storage

app = Flask(__name__)

# Configure this environment variable via app.yaml
CLOUD_STORAGE_BUCKET = os.environ["CLOUD_STORAGE_BUCKET"]


@app.route("/")
def index() -> str:
    return """
<form method="POST" action="/upload" enctype="multipart/form-data">
    <input type="file" name="file">
    <input type="submit">
</form>
"""


@app.route("/upload", methods=["POST"])
def upload() -> str:
    """Process the uploaded file and upload it to Google Cloud Storage."""
    uploaded_file = request.files.get("file")

    if not uploaded_file:
        return "No file uploaded.", 400

    # Create a Cloud Storage client.
    gcs = storage.Client()

    # Get the bucket that the file will be uploaded to.
    bucket = gcs.get_bucket(CLOUD_STORAGE_BUCKET)

    # Create a new blob and upload the file's content.
    blob = bucket.blob(uploaded_file.filename)

    blob.upload_from_string(
        uploaded_file.read(), content_type=uploaded_file.content_type
    )

    # Make the blob public. This is not necessary if the
    # entire bucket is public.
    # See https://cloud.google.com/storage/docs/access-control/making-data-public.
    blob.make_public()

    # The public URL can be used to directly access the uploaded file via HTTP.
    return blob.public_url


@app.errorhandler(500)
def server_error(e: Exception | int) -> str:
    logging.exception("An error occurred during a request.")
    return (
        """
    An internal error occurred: <pre>{}</pre>
    See logs for full stacktrace.
    """.format(
            e
        ),
        500,
    )


if __name__ == "__main__":
    # This is used when running locally. Gunicorn is used to run the
    # application on Google App Engine. See entrypoint in app.yaml.
    app.run(host="127.0.0.1", port=8080, debug=True)

v3.7 and earlier

appengine/flexible_python37_and_earlier/storage/main.py 
from __future__ import annotations

import logging
import os

from flask import Flask, request
from google.cloud import storage

app = Flask(__name__)

# Configure this environment variable via app.yaml
CLOUD_STORAGE_BUCKET = os.environ['CLOUD_STORAGE_BUCKET']


@app.route('/')
def index() -> str:
    return """
<form method="POST" action="/upload" enctype="multipart/form-data">
    <input type="file" name="file">
    <input type="submit">
</form>
"""


@app.route('/upload', methods=['POST'])
def upload() -> str:
    """Process the uploaded file and upload it to Google Cloud Storage."""
    uploaded_file = request.files.get('file')

    if not uploaded_file:
        return 'No file uploaded.', 400

    # Create a Cloud Storage client.
    gcs = storage.Client()

    # Get the bucket that the file will be uploaded to.
    bucket = gcs.get_bucket(CLOUD_STORAGE_BUCKET)

    # Create a new blob and upload the file's content.
    blob = bucket.blob(uploaded_file.filename)

    blob.upload_from_string(
        uploaded_file.read(),
        content_type=uploaded_file.content_type
    )

    # Make the blob public. This is not necessary if the
    # entire bucket is public.
    # See https://cloud.google.com/storage/docs/access-control/making-data-public.
    blob.make_public()

    # The public URL can be used to directly access the uploaded file via HTTP.
    return blob.public_url


@app.errorhandler(500)
def server_error(e: Exception | int) -> str:
    logging.exception('An error occurred during a request.')
    return """
    An internal error occurred: <pre>{}</pre>
    See logs for full stacktrace.
    """.format(e), 500


if __name__ == '__main__':
    # This is used when running locally. Gunicorn is used to run the
    # application on Google App Engine. See entrypoint in app.yaml.
    app.run(host='127.0.0.1', port=8080, debug=True)

Ruby

The sample application presents a web page prompting the user to supply a file to be stored in Cloud Storage. When the user selects a file and clicks submit, the upload handler loads the file content into a blob and writes it to Cloud Storage.

Notice that after the file is uploaded to Cloud Storage, the public URL to this file is returned, which you can use to serve the file directly from Cloud Storage. You should store this value in your app for future use.

require "sinatra"
require "google/cloud/storage"

storage = Google::Cloud::Storage.new
bucket  = storage.bucket ENV["GOOGLE_CLOUD_STORAGE_BUCKET"]

get "/" do
  # Present the user with an upload form
  '
    <form method="POST" action="/upload" enctype="multipart/form-data">
      <input type="file" name="file">
      <input type="submit" value="Upload">
    </form>
  '
end

post "/upload" do
  file_path = params[:file][:tempfile].path
  file_name = params[:file][:filename]

  # Upload file to Google Cloud Storage bucket
  file = bucket.create_file file_path, file_name, acl: "public"

  # The public URL can be used to directly access the uploaded file via HTTP
  file.public_url
end

.NET

The sample application presents a web page prompting the user to supply a file to be stored in Cloud Storage. When the user selects a file and clicks submit, the upload handler loads the file content into a blob and writes it to Cloud Storage.

Notice that after the file is uploaded to Cloud Storage, the public URL to this file is returned, which you can use to serve the file directly from Cloud Storage. You should store this value in your app for future use.

appengine/flexible/CloudStorage/Controllers/HomeController.cs 
    public class HomeController : Controller
    {
        // Contains the bucket name and object name
        readonly CloudStorageOptions _options;
        // The Google Cloud Storage client.
        readonly StorageClient _storage;

        public HomeController(IOptions<CloudStorageOptions> options)
        {
            _options = options.Value;
            _storage = StorageClient.Create();
        }

        [HttpGet]
        public async Task<IActionResult> Index()
        {
            var model = new HomeIndex();
            if (new string[] { null, "", "your-google-bucket-name" }
                .Contains(_options.BucketName))
            {
                model.MissingBucketName = true;
                return View(model);
            }
            try
            {
                // Get the storage object.
                var storageObject =
                    await _storage.GetObjectAsync(_options.BucketName, _options.ObjectName);
                // Get a direct link to the storage object.
                model.MediaLink = storageObject.MediaLink;
                // Download the storage object.
                MemoryStream m = new MemoryStream();
                await _storage.DownloadObjectAsync(
                    _options.BucketName, _options.ObjectName, m);
                m.Seek(0, SeekOrigin.Begin);
                byte[] content = new byte[m.Length];
                m.Read(content, 0, content.Length);
                model.Content = Encoding.UTF8.GetString(content);
            }
            catch (GoogleApiException e)
            when (e.HttpStatusCode == System.Net.HttpStatusCode.NotFound)
            {
                // Does not exist yet.  No problem.
            }
            return View(model);
        }

        [HttpPost]
        public async Task<IActionResult> Index(Form sendForm)
        {
            var model = new HomeIndex();
            // Take the content uploaded in the form and upload it to
            // Google Cloud Storage.
            await _storage.UploadObjectAsync(
                _options.BucketName, _options.ObjectName, "text/plain",
                new MemoryStream(Encoding.UTF8.GetBytes(sendForm.Content)));
            model.Content = sendForm.Content;
            model.SavedNewContent = true;
            var storageObject =
                await _storage.GetObjectAsync(_options.BucketName, _options.ObjectName);
            model.MediaLink = storageObject.MediaLink;
            return View(model);
        }

For more information

For complete information on Cloud Storage, see the Cloud Storage documentation.