OK, sure, 15 minutes could save you 15 percent on your car insurance. But five minutes reading this column could save you 50 percent on your ebooks, apps, movies, music, and TV shows.

Why? Because there’s a new development from Apple, Amazon, and other digital vendors: family sharing. This feature lets you share your online purchases with other people, even if they have their own separate accounts. In theory, these other people are your family members, but there’s nothing to stop you from filling those slots with, say, your friends or roommates.

Family reading digital devices More

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If you and your family members currently use the same Apple or Amazon account, these new sharing features may seem fairly pointless. Up to 10 of you can already freely share the same pool of books, movies, apps, and music on the same Apple account; up to six of you can download the same Kindle books on the same Amazon account (in some cases, publishers set different limits).

But that approach — sharing a single Apple or Amazon account — can get messy. For example, if you and a loved one are reading the same Kindle book on different devices, you’ll constantly lose your place in the book because the service can’t tell you apart. And if you’re sharing your Apple account and password with your kids, then you have no control over what they’re buying (on your credit card). And, of course, your iCloud email, calendar, address book, and iMessages are no longer private.

With the family-sharing plans, you can share the stuff you’ve bought with people who use different Apple or Amazon accounts.

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Consider what’s really going on here: These companies are, in effect, deliberately giving up money, and saving you money. Until now, a husband and wife would have to buy two copies of an ebook if they wanted to read it in their own accounts. A family of four Apple account holders would have to buy a certain app or movie four times if they all wanted it.

Those days are gone now. Common sense has prevailed. Family sharing prevents that duplication of spending.

Apple vs. Amazon: The nitty-gritty

Apple’s Family Sharing plan is far more generous than Amazon’s Family Library feature. Apple lets up to six people (all with different Apple accounts) share everything each has bought: apps, music, TV shows, movies, ebooks. It even lets people see one another’s locations around town (with permission) and creates a shared family category on everyone’s calendars.

You can’t choose which items to share, however – it’s everything or nothing – and all parties have to be running the latest Apple operating systems (iOS 8 on iPhone and iPad, OS X Yosemite on the Mac).

Amazon lets you share only Kindle ebooks, audiobooks, and apps. You can’t share TV shows, movies, or music with this feature. (Amazon says that, later this year, you’ll also be able to share Prime Instant Videos, if you’re a Prime member.)

Furthermore, only two people (adults, each with a different Amazon account) can see each other’s stuff everywhere Kindle books can be read: not just on Kindle e-readers, but also in the Kindle apps on tablets, phones, and computers, and even on the Amazon website.

The adults using Amazon Family Library can also enter the names of four children they can share books with, but the kids can use these books and apps only on certain recent Kindle and Fire models ( here’s the list ).

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