Google DataSaver Proxy is a Firefox add-on that brings Google's popular data compression technology to the Mozilla browser.
Like Opera Turbo, Google DataSaver moves data through Google-owned servers where the data is compressed before sent to the user device.
While compression won't result in any notable gains when it comes to already compressed content such as videos, it cuts data in half or even more when it comes to content that is not compressed yet.
Google DataSaver Proxy for Firefox
Google DataSaver Proxy for Firefox works for the most part like the official Google extension for Chrome. It moves data through Google servers and compresses it there before it lands on the user's device.
Attention: You need to turn off the Data Saver feature using the extension's icon before uninstalling the extension as it won't restore the proxy settings. You can fix the issue manually by loading about:config, searching for network.proxy.http, network.proxy.http_port, and network.proxy.type, right-clicking each preference and selecting reset from the context menu.
Google's solution for Chrome ignores HTTPS traffic and private browsing data. It appears that the solution for Firefox does the same for HTTPS traffic but not for private browsing data.
A quick test revealed that total and saved data counts increased even when private browsing mode was used. The display of data seemed delayed however, and additional tests need to be conducted before a conclusion can be reached.
The Firefox add-on works automatically after installation, and places an icon in the main Firefox toolbar indicating the status of the proxy (on or off).
A click on the icon displays a number of statistics including the save percentage, as well as the total data and compressed data.
Additionally, it lists the day's and monthly savings, and offers to reset those at any time to start anew.
Data Saver pros and cons
Data Saver compresses data before it is transferred. This makes it useful in situations where the Internet connection is not reliable, where it is slow, or where response times from Internet servers are slow.
The gains have to be weight against privacy issues. HTTP Traffic is routed through Google servers after all.