Allows you to specify certain HTTP headers, for example:

gsutil -h "Cache-Control:public,max-age=3600" \
       -h "Content-Type:text/html" cp ...

Note that you need to quote the headers/values that contain spaces (such as “Content-Disposition: attachment; filename=filename.ext”), to avoid having the shell split them into separate arguments.

The following headers are supported: Cache-Control Content-Disposition Content-Encoding Content-Language Content-MD5 Content-Type Custom metadata headers with a matching Cloud Storage Provider prefix, such as:

x-goog-meta-

Note that for gs:// URLs, the Cache Control header is specific to the API being used. The XML API will accept any cache control headers and return them during object downloads. The JSON API respects only the public, private, no-cache, and max-age cache control headers, and may add its own no-transform directive even if it was not specified. See gsutil help apis for more information on gsutil’s interaction with APIs.

See also gsutil help setmeta for the ability to set metadata fields on objects after they have been uploaded.

Causes supported operations (acl ch, acl set, cp, mv, rm, rsync, and setmeta) to run in parallel. This can significantly improve performance if you are performing operations on a large number of files over a reasonably fast network connection.

gsutil performs the specified operation using a combination of multi-threading and multi-processing, using a number of threads and processors determined by the parallel_thread_count and parallel_process_count values set in the boto configuration file. You might want to experiment with these values, as the best values can vary based on a number of factors, including network speed, number of CPUs, and available memory.

Using the -m option may make your performance worse if you are using a slower network, such as the typical network speeds offered by non-business home network plans. It can also make your performance worse for cases that perform all operations locally (e.g., gsutil rsync, where both source and desination URLs are on the local disk), because it can “thrash” your local disk.

If a download or upload operation using parallel transfer fails before the entire transfer is complete (e.g. failing after 300 of 1000 files have been transferred), you will need to restart the entire transfer.

Also, although most commands will normally fail upon encountering an error when the -m flag is disabled, all commands will continue to try all operations when -m is enabled with multiple threads or processes, and the number of failed operations (if any) will be reported at the end of the command’s execution.

WARNING: If you use the gsutil -m option when copying data between versioned buckets, object version ordering will not be preserved. For more information see the “COPYING VERSIONED BUCKETS” section under gsutil help versions .