What `memory_limit` does Magento 2 set?

Magento 2 sets its memory_limit to 768 megabytes:

The Composer library raises its memory limit up to 1 gigabyte:

See also:

From now on, Magento 2 requires 2GB of RAM: http://devdocs.magento.com/guides/v2.0/install-gde/system-requirements-2.0-tech.html#memory-requirement

Upgrading the Magento applications and extensions you obtain from Magento Marketplaces and other sources can require up to 2GB of RAM. If you are using a system with less than 2GB of RAM, we recommend you create a swap file; otherwise, your upgrade might fail.

Please not that the memory_limit PHP option value in the root .htaccess file is still the same, but Magento 2 increases (and even totally disables) it for the most memory intensive tasks.