Is Data Compressed on the iPhone?
In itself, the Apple iPhone doesn't compress the data it transmits over Wi-Fi or over your cellular data network. If you're looking to reduce your monthly bandwidth, however, you aren't limited by the iPhone's capabilities, nor do you have to resort to jailbreaking. Both the Chrome and Opera Web browsers for iOS can compress website data by up to 50 percent. If you want to compress more than website data, an app like Onavo Extend should fit the bill.
1 How Compression Apps Works
The apps on your iPhone don't actually compress the data themselves. Instead, they route the data through the developer's servers before sending it to you. For example, if you want to open a Web page in Chrome, the request is sent through Google's servers, which compress the data in the page, including the images, and then transmits that data to your iPhone. The results, according to developers, is faster browsing and reduced data usage -- by up to five or six times what you have without compression.
Information in this article applies to the Apple iPhone with iOS 7. It may vary slightly or significantly with other versions or products.