So, you want to use S3 to handle image uploads? Here’s the definitive guide, but also see Configure an S3 compatible object storage provider for uploads to see how to configure your app.yml.
S3 registration
Head over to https://aws.amazon.com/free/ and click on 
During the create account process, make sure you provide payment information, otherwise you won’t be able to use S3. There’s no registration fee, you will only be charged for what you use, if you exceed the AWS Free Usage Tier.
Bucket
Go to S3 and click on Create bucket, then fill out the Bucket name. Remember this name because we’ll need it for the next step.
-
The bucket name should not contain periods as this will cause huge HTTPS problems for you.
-
The bucket name should be all lowercase
Name of your bucket
Select a Region. You should enter the location (eg. “EU (Frankfurt)”) that is nearest to your users for better performance.
Scroll down a little until you get to the Permissions panel.
- When you set up the permissions, make sure that you allow public ACLs, otherwise uploads will fail. Uncheck Block all public access and check the bottom two checkboxes. You’ll also have to acknowledge that your settings may make the bucket public in the warning at the top.
User creation
Creating a policy
Sign in to AWS Management Console and search for the “IAM” service to access the AWS Identity and Access Management (IAM) console which enables you to manage access to your AWS resources.
First, click Policies in the sidebar. Then, click on Create Policy and choose the JSON tab:
Use the following piece of code as a template for your policy document:
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": [
"s3:List*",
"s3:Get*",
"s3:AbortMultipartUpload",
"s3:DeleteObject",
"s3:PutObject",
"s3:PutObjectAcl",
"s3:PutObjectVersionAcl",
"s3:PutLifecycleConfiguration",
"s3:CreateBucket",
"s3:PutBucketCORS"
],
"Resource": [
"arn:aws:s3:::=BUCKET=",
"arn:aws:s3:::=BUCKET=/*"
]
},
{
"Effect": "Allow",
"Action": [
"s3:ListAllMyBuckets",
"s3:ListBucket"
],
"Resource": "*"
}
]
}
Make sure that these two lines contain the actual name of your bucket.
If you also intend to do S3 backups, you can include your backup bucket here too like this:
Then click on Review Policy and fill out the Name field. For example, you can call it s3-discourse-policy
Then click on Create Policy at the bottom.
Creating a user account
Now that you’ve created the right policy, you’re ready to create the user account. Click on the Users link on the left side of the IAM console and then the 
button.
Type in a descriptive user name and make sure the “Programmatic access” checkbox is checked.
Setting permissions
The next step in the process is to configure the user’s permissions. Click on the button that says Next: Permissions and then click on «Attach existing policies directly»:
Now search for the policy name you created in the previous step (in our case it’s s3-discourse-policy). When you find it, select the checkbox and click on Next: Tags, then Next: Review, then finally Create user.
Here’s the critical step: Make sure you either download the credentials (Download .csv) or you copy and paste somewhere safe both Access key ID and Secret access key values. We will need them in the next step.
Discourse configuration
Now that you’ve properly set up S3, the final step is to configure your Discourse forum. These instructions should work, but the preferred method is to use environment variables and a CDN as described in Configure an S3 compatible object storage provider for uploads.
Make sure you’re logged in with an administrator account and go the Settings section in the admin panel.
Type in “S3” in the textbox on the right to display only the relevant settings:
You will need to:
- Check the “
enable s3 uploads” checkbox to activate the feature - Paste in both “
Access Key Id” and “Secret Access Key” in their respective text fields - Enter
=BUCKET=in the “s3 upload bucket” field
You need to append a prefix to the bucket name if you want to use the same bucket for uploads and backups.
Examples of valid bucket settings
-
Different buckets
- s3_upload_bucket:
=BUCKET= - s3_backup_bucket:
=BACKUPS=
- s3_upload_bucket:
-
Different prefixes
- s3_upload_bucket:
=BUCKET=/uploads - s3_backup_bucket:
=BUCKET=/backups
- s3_upload_bucket:
-
Prefix for backups
- s3_upload_bucket:
=BUCKET= - s3_backup_bucket:
=BUCKET=/backups
- s3_upload_bucket:
The “s3_region” setting is optional and defaults to “US East (N. Virginia)”. You should enter the location (eg. “EU (Frankfurt)”) that is nearest to your users for better performance. If you created the bucket manually, you’ll need to select the region you selected during the creation process.
Enjoy
That’s it. From now on, all your images will be uploaded to and served from S3.
Backups
Do you want store backups of your Discourse forum on S3 as well? Take a look at Configure automatic backups for Discourse.
Frequently Asked Questions
I reused the same bucket for uploads and backups and now backups aren’t working. What should I do?
Name of your bucket for backups
The easiest solution is to append a path to the s3_backup_bucket. Here’s an example of how your settings should look afterwards.
s3_upload_bucket:=BACKUPS=s3_backup_bucket:=BACKUPS=/backups
You can use the S3 Console to move existing backups into the new folder.
Do I really need to use separate buckets for uploads and backups?
No, you don’t, but it’s usually the easiest way to set-up. Essentially you need to either use two different buckets or a prefix for the backup bucket. For example, the following combinations will work:
-
Different buckets
- s3_upload_bucket:
=BUCKET= - s3_backup_bucket:
=BACKUPS=
- s3_upload_bucket:
-
Different prefixes
- s3_upload_bucket:
=BUCKET=/uploads - s3_backup_bucket:
=BUCKET=/backups
- s3_upload_bucket:
-
Prefix for backups (not recommended unless you previously reused the same bucket – see above question)
- s3_upload_bucket:
=BACKUPS= - s3_backup_bucket:
=BACKUPS=/backups
- s3_upload_bucket:
I’ve enabled S3 uploads in my Discourse instance (which has been going for a while); what do I do with the existing local uploads?
To migrate your existing uploads to S3, you can do a couple of rake tasks. To perform this, you need SSH access, root permissions, and have entered the discourse app (as per Administrative Bulk Operations). Oh, and you have to set some environmental variables in app.yml. Not for the faint-hearted.
Once you have done all that you are ready for the rake tasks:
rake uploads:migrate_to_s3
Once that is done, posts that need to be rebaked will be marked accordingly and will be rebaked by a regular task. If you have resources and are in a hurry, you can issue this command (which is recommended by the above rake task):
rake posts:rebake_uncooked_posts
Once the posts are all rebaked (and the uploads are working well) you no longer need to include uploads in your backups. And as a bonus, you will be able to Restore a backup from the command line in the event of catastrophe (just keep a copy of app.yml somewhere).
One-way door
Unlike many configuration decisions in Discourse, note that using S3 is a “one-way door;” that is, a move that cannot easily be reversed. There is no safe or maintained way to move files out of S3 to be in the local uploads. In particular, the migrate_to_s3 moves more than just post images to S3; files for which there is no reverse path. (For more details, see Migrate_from_s3 problems).
Backing up your S3 assets
Using versioning, or syncing to a different region are all good strategies.
