WordPress plugin to store uploads on S3

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3.0.7 2023-05-04 08:22 UTC


S3 Uploads
Lightweight "drop-in" for storing WordPress uploads on Amazon S3 instead of the local filesystem.
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A Human Made project. Maintained by @joehoyle.

S3 Uploads is a WordPress plugin to store uploads on S3. S3 Uploads aims to be a lightweight "drop-in" for storing uploads on Amazon S3 instead of the local filesystem.

It's focused on providing a highly robust S3 interface with no "bells and whistles", WP-Admin UI or much otherwise. It comes with some helpful WP-CLI commands for generating IAM users, listing files on S3 and Migrating your existing library to S3.


  • PHP >= 7.1
  • WordPress >= 5.3

Getting Set Up

S3 Uploads requires installation via Composer:

composer require humanmade/s3-uploads

Note: Composer's autoloader must be loaded before S3 Uploads is loaded. We recommend loading it in your wp-config.php before wp-settings.php is loaded as shown below.

require_once __DIR__ . '/vendor/autoload.php';


Once you've installed the plugin, add the following constants to your wp-config.php:

define( 'S3_UPLOADS_BUCKET', 'my-bucket' );
define( 'S3_UPLOADS_REGION', '' ); // the s3 bucket region (excluding the rest of the URL)

// You can set key and secret directly:
define( 'S3_UPLOADS_KEY', '' );
define( 'S3_UPLOADS_SECRET', '' );

// Or if using IAM instance profiles, you can use the instance's credentials:

Please refer to this region list for the S3_UPLOADS_REGION values.

Use of path prefix after the bucket name is allowed and is optional. For example, if you want to upload all files to 'my-folder' inside a bucket called 'my-bucket', you can use:

define( 'S3_UPLOADS_BUCKET', 'my-bucket/my-folder' );

You must then enable the plugin. To do this via WP-CLI use command:

wp plugin activate S3-Uploads

The plugin name must match the directory you have cloned S3 Uploads into; If you're using Composer, use

wp plugin activate s3-uploads

The next thing that you should do is to verify your setup. You can do this using the verify command like so:

wp s3-uploads verify

You will need to create your IAM user yourself, or attach the necessary permissions to an existing user, you can output the policy via wp s3-uploads generate-iam-policy

Listing files on S3

S3-Uploads comes with a WP-CLI command for listing files in the S3 bucket for debugging etc.

wp s3-uploads ls [<path>]

Uploading files to S3

If you have an existing media library with attachment files, use the below command to copy them all to S3 from local disk.

wp s3-uploads upload-directory <from> <to> [--verbose]

For example, to migrate your whole uploads directory to S3, you'd run:

wp s3-uploads upload-directory /path/to/uploads/ uploads

There is also an all purpose cp command for arbitrary copying to and from S3.

wp s3-uploads cp <from> <to>

Note: as either <from> or <to> can be S3 or local locations, you must specify the full S3 location via s3://mybucket/mydirectory for example cp ./test.txt s3://mybucket/test.txt.

Private Uploads

WordPress (and therefor S3 Uploads) default behaviour is that all uploaded media files are publicly accessible. In certain cases which may not be desireable. S3 Uploads supports setting S3 Objects to a private ACL and providing temporarily signed URLs for all files that are marked as private.

S3 Uploads does not make assumptions or provide UI for marking attachments as private, instead you should integrate the s3_uploads_is_attachment_private WordPress filter to control the behaviour. For example, to mark all attachments as private:

add_filter( 's3_uploads_is_attachment_private', '__return_true' );

Private uploads can be transitioned to public by calling S3_Uploads::set_attachment_files_acl( $id, 'public-read' ) or vica-versa. For example:

S3_Uploads::get_instance()->set_attachment_files_acl( 15, 'public-read' );

The default expiry for all private file URLs is 6 hours. You can modify this by using the s3_uploads_private_attachment_url_expiry WordPress filter. The value can be any string interpreted by strtotime. For example:

add_filter( 's3_uploads_private_attachment_url_expiry', function ( $expiry ) {
	return '+1 hour';
} );

Cache Control

You can define the default HTTP Cache-Control header for uploaded media using the following constant:

define( 'S3_UPLOADS_HTTP_CACHE_CONTROL', 30 * 24 * 60 * 60 );
	// will expire in 30 days time

You can also configure the Expires header using the S3_UPLOADS_HTTP_EXPIRES constant For instance if you wanted to set an asset to effectively not expire, you could set the Expires header way off in the future. For example:

define( 'S3_UPLOADS_HTTP_EXPIRES', gmdate( 'D, d M Y H:i:s', time() + (10 * 365 * 24 * 60 * 60) ) .' GMT' );
	// will expire in 10 years time

Default Behaviour

As S3 Uploads is a plug and play plugin, activating it will start rewriting image URLs to S3, and also put new uploads on S3. Sometimes this isn't required behaviour as a site owner may want to upload a large amount of media to S3 using the wp-cli commands before enabling S3 Uploads to direct all uploads requests to S3. In this case one can define the S3_UPLOADS_AUTOENABLE to false. For example, place the following in your wp-config.php:

define( 'S3_UPLOADS_AUTOENABLE', false );

To then enable S3 Uploads rewriting, use the wp-cli command: wp s3-uploads enable / wp s3-uploads disable to toggle the behaviour.

URL Rewrites

By default, S3 Uploads will use the canonical S3 URIs for referencing the uploads, i.e. [bucket name][file path]. If you want to use another URL to serve the images from (for instance, if you wish to use S3 as an origin for CloudFlare), you should define S3_UPLOADS_BUCKET_URL in your wp-config.php:

// Define the base bucket URL (without trailing slash)
define( 'S3_UPLOADS_BUCKET_URL', 'https://your.origin.url.example/path' );

S3 Uploads' URL rewriting feature can be disabled if the current website does not require it, nginx proxy to s3 etc. In this case the plugin will only upload files to the S3 bucket.

// disable URL rewriting alltogether

S3 Object Permissions

The object permission of files uploaded to S3 by this plugin can be controlled by setting the S3_UPLOADS_OBJECT_ACL constant. The default setting if not specified is public-read to allow objects to be read by anyone. If you don't want the uploads to be publicly readable then you can define S3_UPLOADS_OBJECT_ACL as one of private or authenticated-read in you wp-config file:

// Set the S3 object permission to private
define('S3_UPLOADS_OBJECT_ACL', 'private');

For more information on S3 permissions please see the Amazon S3 permissions documentation.

Custom Endpoints

Depending on your requirements you may wish to use an alternative S3 compatible object storage system such as Minio, Ceph, Digital Ocean Spaces, Scaleway and others.

You can configure the endpoint by adding the following code to a file in the wp-content/mu-plugins/ directory, for example wp-content/mu-plugins/s3-endpoint.php:

// Filter S3 Uploads params.
add_filter( 's3_uploads_s3_client_params', function ( $params ) {
	$params['endpoint'] = '';
	$params['use_path_style_endpoint'] = true;
	$params['debug'] = false; // Set to true if uploads are failing.
	return $params;
} );

Temporary Session Tokens

If your S3 access is configured to require a temporary session token in addition to the access key and secret, you should configure the credentials using the following code:

// Filter S3 Uploads params.
add_filter( 's3_uploads_s3_client_params', function ( $params ) {
	$params['credentials']['token'] = 'your session token here';
	return $params;
} );

Offline Development

While it's possible to use S3 Uploads for local development (this is actually a nice way to not have to sync all uploads from production to development), if you want to develop offline you have a couple of options.

  1. Just disable the S3 Uploads plugin in your development environment.
  2. Define the S3_UPLOADS_USE_LOCAL constant with the plugin active.

Option 2 will allow you to run the S3 Uploads plugin for production parity purposes, it will essentially mock Amazon S3 with a local stream wrapper and actually store the uploads in your WP Upload Dir /s3/.


Created by Human Made for high volume and large-scale sites. We run S3 Uploads on sites with millions of monthly page views, and thousands of sites.

Written and maintained by Joe Hoyle. Thanks to all our contributors.

Interested in joining in on the fun? Join us, and become human!