Update: Mailbox just received the expected update with Dropbox integration for attachments.

Dropbox kicked off its developer conference in San Francisco today and with it came a few updates including new tools for devs and the announcement that the service now has 175 million users. That’s up about 75 million users from just last November.

The developer conference also included some announcements about new tools coming to let third-party app and website developers easier integrate Dropbox. The company is introducing a platform for developers that includes a new API called Datastores, allowing app devs to store and sync data from their apps across multiple devices and platforms. It’s something developers have been doing on their own for a while (for example 1Password), but now Dropbox is making easy for all:

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The Datastore API provides developers a new way to sync data beyond files across a variety of devices and platforms. The Datastore API allows developers to save their app’s structured data (e.g. contacts, to-do items, and game state) on Dropbox and handles all the magic necessary to sync it quickly and reliably. Users of a Datastore-enabled app can be sure their data will be up-to-date across all their devices whether online or offline.

It also showed off new “Drop-ins” that will let devs easily integrate the ability to open and save from Dropbox within their apps:

Drop-ins are cross-platform UI components that can be integrated in minutes. The Chooser provides web and mobile apps with instant access to files in Dropbox, and the Saver makes saving files to Dropbox one-click simple.

The first app to take advantage of the functionality is Dropbox’s Mailbox iOS client that will soon receive, which just received an update with the ability to attach files from Dropbox to emails.