As soon as your collection of Apple devices running OS X or iOS expands to two or more, the issue of syncing is bound to come up. You'll want most or all of the important personal data on your first device--e-mail, calendars, contacts, notes, and more--to be identical on your second device, and you'll want to be able to update the data in either place and have the changes reflected in the other.
That basic scenario isn't difficult to achieve, but it gets more complicated as the number of variables increases. Add more data types, more devices, different operating systems and versions, cloud-based services, push sync, and other niceties, and pretty soon you have an inscrutable tangle of connections.
So, to keep the process as straightforward as possible, here are some ground rules for this article:
* I'll assume your Mac(s) run OS X 10.6 Snow Leopard and mobile device(s) run iOS 4 (but see "What About iOS 3 and OS X 10.5?" if your device uses an older operating system).
* I talk only about syncing Apple's applications--Mail, Address Book, iCal, Safari, and so on--not third-party applications, which add numerous complexities.
* This guide covers e-mail, contacts, calendars, to-do items, notes, and browser bookmarks--but not other data types you may want to sync.
* I discuss syncing data only for a single user between multiple devices that person uses--not syncing data between multiple users (but see "Other sync options" for some suggestions about multi-person synchronization).
* The focus here is primarily on just two methods of syncing all your data: using Apple's MobileMe service ($99 a year for individuals, $149 for the five-user Family Pack, although you can usually find it for less from places such as Amazon.com), and using a variety of free services from Google--Gmail, Gmail Contacts, Google Calendar, and Gmail Tasks. (For help deciding which to use, see "Choosing between MobileMe and Google.")
I'll also offer one general piece of advice at the outset: Instead of turning on all types of syncing on all your devices at once, concentrate on getting just one type of data syncing between two devices, gradually add the rest of your devices, and then repeat the procedure for each data type.
Syncing with MobileMe
MobileMe is best known for its highly visible services such as e-mail and iDisk, but one of its most impressive talents is keeping many kinds of data in sync among multiple Macs and iOS devices. Because Apple's servers function as both mediator and online storage for all your synchronized data, you can also access your information in a Web browser on almost any Internet-connected device at http://www.me.com/. And the entire process is easy to set up, too, although not without occasional glitches.
Before you start experimenting with changes in your sync setup, I recommend that you back up your Mac--most crucially your calendar and contact data, which are especially vulnerable to accidental change or deletion. If you already use Time Machine or a cloning utility such as Super Duper ($28), you're all set. Otherwise, to back up the contents of the OS X Address Book, open Address Book (in /Applications), choose File -> Export -> Address Book Archive, enter a name and choose a location for the exported data (preferably on a different disk), and click Save. To back up your iCal calendars, open iCal (in /Applications), choose File -> Export -> iCal Archive, enter a name and choose a location for the exported data, and click Save. If you're using an iPhone, iPad, or iPod touch, attach it to your Mac using its USB cable or dock and allow it to sync before proceeding.
Basic setup On a Mac, open the MobileMe pane of System Preferences. If the window shows Member Name and Password fields, fill them in and click Sign In. Next, click the Sync tab and select the Synchronize With MobileMe checkbox. The pop-up menu provides several options for synchronization frequency. The default choice, Automatically, is what Apple recommends (as do I). For most data types, this setting means that when data changes on your Mac, it's pushed to Apple's servers immediately, and when changes are made elsewhere, they're retrieved from Apple's servers quickly--usually within seconds. (Some types of data, including keychains and preferences, which I don't cover here, follow a more relaxed automatic syncing schedule.)
You'll also need to select the checkbox for each type of data you want to sync. For our purposes, that means (at least) Bookmarks, Calendars, Contacts, and Notes. Read on for further details, but remember that it never hurts to activate and test these one at a time. Finally, make sure Show Status In Menu Bar is selected; that displays the Sync menu (an icon with two arrows arranged in a circle) in your menu bar, which will come in handy later on.
On an iOS 4 device, if you don't already have a MobileMe account set up, tap Settings -> Mail, Contacts, Calendars -> Add Account -> MobileMe, enter your credentials, and tap Next. After iOS verifies your information, it displays a series of services you can turn on or off, but you can leave everything set at its default for now, and simply tap Done.
E-mail MobileMe addresses the problem of syncing e-mail in two different ways. First, your MobileMe e-mail account uses IMAP (Internet message access protocol). With IMAP, the mail server always contains a master copy of all your messages and mailboxes--including sent and filed e-mail (not to mention status flags such as read/unread, forwarded, and replied to). So, set up multiple clients using the same credentials, and after they've had time to sync, they'll show exactly the same mailboxes and messages. (Microsoft Exchange ActiveSync is a different protocol that offers similar benefits.)
Second, MobileMe lets you sync the settings for all your accounts (not just MobileMe) between devices, although it doesn't sync the messages themselves. If all your accounts are of the IMAP and Exchange varieties, syncing is simple because MobileMe handles syncing account settings, while Mail syncs the messages themselves with the servers. (If you have any POP accounts, syncing messages between Macs is more involved; read more in "Sync your e-mail messages.")
In the Sync view of the MobileMe pane of System Preferences are two checkboxes having to do with Mail: Mail Accounts; and Mail Rules, Signatures, And Smart Mailboxes. When you select Mail Accounts on two or more Macs, OS X synchronizes the basic settings (such as server addresses and e-mail addresses) for all your e-mail accounts between them. This setting does not sync your passwords, though; if you store your Mail passwords in your Keychain, you can select Keychains, separately, to sync those too. The result is that, for IMAP and Exchange accounts, both Macs will download and display identical copies of the messages from the respective servers. (Messages stored locally in "On My Mac" mailboxes don't sync via MobileMe.)
When you select Mail Rules, Signatures, And Smart Mailboxes, those portions of Mail's preferences sync between the Macs. This is usually helpful, but if two Macs have different sets of active accounts or local mailboxes, some of your rules, signatures, and smart mailboxes may not work correctly.
Although MobileMe syncs Mail settings between Macs, it doesn't sync Mail settings to your iOS devices; instead, iTunes does that job. With your iOS device attached via USB, open iTunes, select your device in the Devices section of the sidebar, and click the Info tab. Select Sync Mail Accounts, along with each e-mail account on your Mac for which you'd like to transfer settings to your iOS device. Then click Sync.
Once you've done this, go to Settings -> Mail, Contacts, Calendars on your iOS device, tap your MobileMe account, and make sure the Mail switch is set to On. Repeat this procedure for each server-based account you want to sync.
In addition--still on the Mail, Contacts, Calendars screen--make sure Fetch New Data is set to Push if you want data such as e-mail, calendars, and contacts to update immediately on your iPhone when they change on another device. (If not, tap Fetch New Data and tap the switch next to Push.) Push decreases battery life; if that's your top concern, leave Push turned off and choose the frequency with which you want to fetch new data.
Assuming your settings are correct, your Internet connection is active, and you've waited long enough for any messages on the server to download to each of your Macs, your e-mail should now be in sync. On iOS devices, Mail doesn't automatically download all the messages in all your mailboxes; it downloads the contents of your Inboxes (up to the limit specified in Settings -> Mail, Contacts, Calendars -> Show), and then it downloads the contents of any individual mailbox (again, up to the limit you set) when you select it.
Contacts To sync your contacts via MobileMe, make sure the Contacts checkbox is selected in the Sync view of the MobileMe pane of System Preferences. OS X then syncs all the local ("On My Mac") contacts between your Mac(s) and Apple's servers. Contacts on LDAP servers, or in CardDAV or Exchange 2007 accounts, don't sync via MobileMe; you must set up these accounts separately on each device.
To enable over-the-air contact syncing for your MobileMe account on an iOS device, tap Settings -> Mail, Contacts, Calendars, tap your MobileMe account, and make sure Contacts is set to On. To sync with Exchange accounts as well, tap their names in the list of e-mail accounts and likewise ensure that Contacts is turned on.
Calendars MobileMe can sync the calendars you created on your Mac(s) in iCal with Apple's servers, to other Macs, and to your iOS devices. Apple's newly revised calendar system for MobileMe uses the industry-standard CalDAV protocol for syncing calendar data (just as Google does) rather than relying on a proprietary mechanism as MobileMe did in the past. This should make calendar syncing more robust and flexible.
However, because the new Calendar is significantly different from the old one and requires some extra set-up steps, Apple hasn't switched everyone over automatically. To use the new CalDAV-based system, those who didn't participate in the beta testing must sign in to the MobileMe Web site, go to the Calendar application, click Upgrade Now, and follow the directions Apple provides there. Then continue with the following steps.
On each Mac, make sure Calendars is selected in the Sync view of the MobileMe pane of System Preferences. Note that MobileMe syncs only local ("On My Mac") calendars and read-only calendars to which you've subscribed. (Subscribed calendars appear only on other Macs and iOS devices, not on the MobileMe Web site.) If you've set up any server-based calendar accounts, such as CalDAV or Exchange 2007, these won't sync via MobileMe; you'll have to configure such accounts individually on each device.
On an iOS 4 device, go to Settings -> Mail, Contacts, Calendars -> Your MobileMe Account and make sure Calendars is turned on. After turning it on initially, you may see a prompt asking how to treat existing calendar data. If so, "Merge with MobileMe" is the correct choice.
To-Do items OS X considers to-do items, or tasks, to be calendar data, and therefore they appear in iCal. (If your tasks aren't visible, choose View -> Show To Do List or press Command-Option-T.) Starting with OS X 10.5, Mail can also create and display to-do items, using the same calendars as iCal. To create a new to-do item in Mail, click the To Do button in the toolbar; tasks then appear in the To Do list under Reminders in the sidebar. (I discuss the use of to-do items, as well as notes, in Mail in "Master Mail's reminders.")
As a result, as long as you sync Calendars as described above, your to-do items will come with them. You can then access them in the Calendar app on the MobileMe Web site (if you don't see your tasks, choose Show To Do List from the gear-shaped pop-up Action menu), or in iCal on another Mac.
Unfortunately, for reasons I've never understood, Apple provides no way to access to-do items on an iOS device. They don't appear in the Calendar app, and there's no separate Tasks app either. If you want to sync to-do items with your iOS device, you must turn to third-party software (see "Other sync options").
Notes Along with to-do items, Mail lets you store notes--lists, thoughts, and other random snippets of information. You can create a note by clicking the New Note button in Mail's toolbar; it then appears in the Notes list under Reminders in the sidebar (and potentially in your Inbox as well, depending on your preferences). In iOS 4, Mail's notes can sync wirelessly with the Notes app on your iOS device too (see "Syncing iPhone notes to MobileMe" for more details). However, there's a catch or two.