Compose an object

The compose operation creates a new object whose contents are the concatenation of a given sequence of up to 32 source objects. The source objects must all reside in the same bucket and use the same storage class. The source objects are unaffected by the compose operation, and the resulting composite object does not change if its source objects are replaced or deleted.

Composite objects may be built from source objects that are themselves composite objects.

For more information, see Composite Objects.

Query string parameters

Parameter Description Required
compose Issues a compose request. Requires a ComposeRequest XML document in the request body. No

See signed URL query string parameters for information on the parameters you include when creating and using signed URLs.

Request headers

In addition to common request headers, the following can be used.

Header Description Required
Content-Encoding The compression algorithm that was used to compress the composite object. No
Content-Disposition A header that specifies presentational information about how the object data is to be transmitted. No
x-goog-acl The predefined ACL that you want to apply to the composite object. No
x-goog-custom-time A user-specified date and time. No
x-goog-encryption-kms-key-name The customer-managed encryption key to use to encrypt the composed object. No
x-goog-meta- An extension header that can be used to store custom metadata. No

Mode of the object's retention configuration. GOVERNANCE corresponds to unlocked mode, and COMPLIANCE corresponds to locked mode.

If this header is specified, x-goog-object-lock-retain-until-date must also be specified.


A date and time represented in RFC 3339 UTC format that determines the time until which the object is retained as immutable.

If this header is specified, x-goog-object-lock-mode must also be specified.


To compose objects encrypted by a customer-supplied encryption key, use the headers listed on the Encryption page in your request.

Request body elements

The following request body elements are applicable only if you use the compose query string parameter to issue a compose request.

Element Description
ComposeRequest Container for a compose request.
Component Container for a compose request component argument.
Name Object name for a compose request component.
Generation Generation number for a compose request component.
IfGenerationMatch Expected current generation number for a compose request component. The request will fail if the component object has a different generation.

Request syntax

Date: DATE


Response headers

The request can return a variety of response headers depending on the request headers you use.

Response body elements

The response does not include an XML document in the response body.