Applications to take notes, make to-do lists, shopping or that allow us to write annotations to consult later, there are tons in the Google Play Store, but that are multiplatform very few, if we count the applications of this type that are paid.
Google Keep has become a excellent tool for many users who habitually take notes of what comes to mind, write down their work or home tasks or use it as an application to write documents or drafts that later have to be formatted with another application to clear it.

Google Keep has just surpassed 500 million downloads on the Play Store, thus confirming that it is an excellent tool when making notes, lists or any other utility that we can give it.
This application, it does not come installed within Google applications in Android-based terminals that reach the market, so reaching this figure calls even more attention.
Google Keep is available on all mobile ecosystems, through its own application and on computers, through the desktop version, so it is available from any ecosystem that comes to mind.
Interesting and free alternative to Google Keep
But if you have tried again and again and Google Keep does not quite meet your needs, you have another completely free application like Microsoft To-Do, an application that also allows us to make any type of annotation or list and that is also accessible from any ecosystem, whether mobile or desktop, although in this not via the web like Google Keep, but through its own application available both in Windows as well as Mac.
If you think that the time has come to use this application / service then I leave you in direct download link to the Play Store. If you want to try Microsoft To-Do, I also leave you the direct download link to the application.