Picasa was first released in 2002, as a tool to catalog and edit photos. In 2004, Google acquired the company and began offering both Windows and Mac OS native apps for free.
Picasa Web Albums was a well-known feature of Picasa that allowed users to share photo albums with friends and family.
In 2016, Google decided to shut down Picasa and Picasa Web Albums.
As stated in this article written by Google, the decision to shut down Picasa was part of their efforts to focus on Google Photos, a newer photo-sharing/storage service.
"After much thought and consideration, we’ve decided to retire Picasa over the coming months in order to focus entirely on a single photo service in Google Photos. We believe we can create a much better experience by focusing on one service that provides more functionality and works across mobile and desktop, rather than divide our efforts across two different products."
From 15th March 2016 onwards, Picasa’s desktop app stopped receiving updates (but it continued to work). As for Picasa Web Albums, it was shut down on 1st May 2016.
Picasa’s users went crazy to find which tool to move on to. Google Photos was the recommendation from Google, but the services had some differences (more on that below).
Some other alternative apps are Windows and MacOs Photos Gallery, Adobe Lightroom, Photoscape, Dropbox, and Flickr. Make sure to check this article to find out more alternatives, as well as the differences between them.
Many users struggled to adapt to Google Photos, as Picasa was different.
One of the common critics has been how slow does Google Photos charge your photos as you browse through the app. Picasa, on the other hand, displayed all the images at a glance.
Another critic was that Picasa was a desktop program with cloud storage. Google Photos, instead, is a mobile or web app, with cloud storage.