Last week, the messaging app Snapchat announced updates to its privacy policy, specifically regarding the reuse of photos included in the social media platform’s “Live Story” feature. Users were outraged to hear Snapchat would reuse their posts, especially considering that the company’s main attraction is that all posts “disappear” within seconds and are ultimately deleted from Snapchat’s servers.

We asked Jessica Silbey, a law professor at Northeastern and a leading expert on intellectual property, to explain the ins and outs of the updates as well as the privacy policies of other social media platforms.

Part of Snapchat’s revised policy language says “you grant Snapchat a worldwide, perpetual license to exhibit and publicly display the content in any form in any and all media.” What, exactly, does this mean? And what should Snapchat users know about how much privacy they do—or don’t—retain when using the app?

Snapchat has not changed its privacy settings but it has attempted to render them in “plain English,” which ironically has caused concern among its users. Snapchat’s system still deletes messages when received and viewed by another or when the message expires, whichever is sooner.

But this new rendition of its Terms of Service also explains that if you add your photos to the public “Live Story” feed, Snapchat has the right to show the photos around the world and even replay them at later times. This is not something that has changed from previous policies, but is rather made clearer by this new “plain English” version. The “perpetual license to exhibit and publicly display” refers to these photos users agree to make public through “Live Story.”

It is an affirmative opt-in policy, which means if your privacy settings remain private, Snapchat has no right to republish or display your photos. This, however, does not prevent other users to whom the messages are sent from doing so. Screen shots and forwards of messages remain entirely possible—and likely—making the “privacy” of one’s messages largely up to the grace of addressees.

What advice would you offer students and others who use Snapchat and other messaging apps regarding their privacy?

I would remind anyone using social media that there is no such thing as secure privacy online. A sender loses control the instant a message or photo is sent. Messaging apps and media platforms contribute to the virality and lack of privacy that exists online, but in the end we are the only ones who can control what others see. If you don’t want your message tweeted or shared or forwarded by another, don’t post, send, or tweet in the first place. The Internet is a public place.

What are the major differences between privacy rights on the various social media platforms—from Facebook to Twitter to Snapchat to Instagram?

One major difference is the ability to control who receives your message. On Facebook and Instagram, you can approve or reject friends or followers. Snapchat is more of a one-to-one message service with the ability to form groups. All platforms have decent anti-harassment mechanisms for reporting cyberbullying.

Snapchat is the only platform that promises not to store nor “learn” from your private messages and to delete them upon receipt; it contends it is not the “holder” or “host” of much content but more like a conduit. Facebook, Instagram, and Twitter do not own what users post, but each company effectively culls the messages and login information for useful data to monetize.