Setting Object Headers

This guide explains how to set headers for S3 objects using s3cmd and aws s3api. This is useful for managing caching, adding custom metadata, and optimizing bucket data handling.

Setting Headers via Dashboard

Copy link

1. Go to the S3 storage section and click on the bucket.
2. In the Objects tab, click on the three dots next to the object and select Edit metadata.

3. Add necessary headers. To set up a custom header, click +Add.

Available Parameters

Copy link

You can configure the following parameters.

Content-Type

The MIME type of the object's content. It defines the file format and is used by client applications to process the file correctly.

Example values:

• application/pdf: PDF document
• image/jpeg: JPEG image
• text/plain: plain text file
• application/json: JSON document

If an incorrect value is set, browsers or applications may fail to identify the file type properly.

Cache-Control

Controls how the object is cached by browsers, CDNs, and intermediate proxy servers.

Example: max-age=3600

In this case, the object can be stored in cache for 3600 seconds (1 hour) without making a new request to the storage.

Content-Encoding

Specifies the encoding applied to the object's content.

Example: gzip

Used for files that were compressed before being uploaded to storage. When the object is retrieved, the client can automatically decompress the content.

Content-Disposition

Defines how the file is handled when downloaded.

Common values:

• attachment: prompt the user to save the file
• inline: attempt to open the file directly in the browser

For example, for PDF documents, inline opens the file in a browser tab, while attachment triggers a download.

Custom Metadata

Lets you attach arbitrary key-value pairs to an object.

To add custom metadata, click Add and fill in the fields:

• Key: the metadata name. Custom metadata keys are stored with the x-amz-meta- prefix.
• Value: an arbitrary metadata value.

Examples:

You can add multiple custom metadata entries to a single object.

Custom metadata does not affect file contents, but can be used by applications to store additional information about an object, classify it, or drive processing logic.

Setting Headers via CLI

Copy link

Another way to configure headers is to use utilities like s3cmd or s3api.

Setting a Header for a Single Object

Copy link

To set a header for a specific object, use the s3cmd modify command. For example, to add a Cache-Control header to a specific object:

s3cmd modify s3://<bucket_name>/<object_name> --add-header="cache-control:max-age=7000"

In this case, the object will receive the Cache-Control header with the max-age=7000 parameter, instructing browsers or proxy servers to cache the object for 7000 seconds.

Setting Headers for All Objects in a Bucket

Copy link

To set headers for all objects in a bucket, you can use the --recursive option to apply changes to all files:

s3cmd modify --recursive s3://<bucket_name> --add-header="cache-control:max-age=7001"

This command recursively adds the Cache-Control header with the value max-age=7001 to all objects in the bucket.

Creating a Custom Header

Copy link

To add custom headers, use the s3cmd modify command with the x-amz-meta prefix:

s3cmd modify s3://<bucket_name>/<object_name> --add-header="x-amz-meta-test-header:test"

This creates a custom header x-amz-meta-test-header with the value test. In the object's metadata, the header will appear without the x-amz-meta- prefix, resulting in:

"Metadata": {
    "test-header": "test"
}

This allows you to store additional data in the object, which can be useful for processing or logging.

Verifying Set Headers

Copy link

To verify the headers, use the aws s3api head-object command. This ensures that all headers and metadata have been successfully added:

aws s3api head-object --bucket <bucket_name> --key <object_name> --endpoint-url https://s3.hmstorage.net

The command will return information about the object, including its metadata and headers, allowing you to confirm that the changes were applied correctly.