Optimising images for your website can be a bit of a black art, but it’s well worth doing as the bandwidth savings can be large. It will also make a big difference to the speed at which your site loads.
These days many of us have access to very fast broadband (we typically have 100Mb/s connections here at thoughtbot) but not everybody has access to this sort of connection. Most people worldwide are still stuck on relatively slow ADSL packages that run at no more than 2Mb/s or so.
Mobile connections have come a long way in recent years, but the variability of speed is even worse than wired connections. 4G can be as fast as good broadband, but in areas with high contention or in areas where there is no 3G or 4G mobile connections can be as slow as mud.
Whatever the speed of the connection it’s worth optimising your images as visitors are far more likely to abandon your site if it takes more than a few seconds to load and search engines will rank your site higher if it loads quickly. It’s also worth remembering that even fast broadband connections often have data caps.