Jumping straight to numbers and facts it saved me at least 20% of my data for two months consecutively; without any noticeable drop in load time or a drop in the quality of experience — except for a slight loss of image quality due to compression (which I think was completely reasonable given the savings).
Data is a big deal. Specially if your internet service provider doesn’t carry an unlimited package and/or if you come up close or beyond your package limits every month — in which case saving even a small percentage of your usage can really come in handy.
I’ve dealt with this issue every month for several years and so far the most successful tool I’ve used to ‘compress’ my data is the Data Saver Chrome plugin offered by Google (beta version at the time of writing).
So to give you an idea of my daily internet usage – it mostly includes browsing blogs, art sites (like DeviantArt – mostly heavy on images), work related (email/docs/research/web development), light on YouTube and social media. I sounds pretty grey — but I rely on the internet heavily for work, study and entertainment; and this is just one computer. Data saver managed to save me at least 20% of my usage in this scenario for two consecutive months.
The second scenario was another computer in which usage was mostly rich-media content — mainly YouTube and relatively light on other content. Out of a total* ~7.8 GB* usage the plugin only saved up-to 5.7% of the data for two consecutive months. The perfectly reasonable explanation for this is that plugin does not compress secure pages (HTTPs); and the key usage in this scenario (which was YouTube) comes uncompressed.
*So in conclusion: *The plugin can do wonders if your main internet usage is work and/or study (fewer secure pages with rich-media content), and could save you as much as 45% on usage (based on the plugin preview on the web store). But even if you don’t it can save you some amount of data without getting in your way in anyway, and if you’re billed by usage you could effectively cut between 5% – 20% off of your bill based on my results!
Give it a try at Data Saver.