Background: Online platforms have nowadays been more developed and used by the population. For this reason, companies use to share more information through them. Moreover, the interest in sustainability also increases by people. Therefore, companies are trying to communicate sustainability through different techniques and actions.

Problem: we have noticed that companies create different content depending on which social media are they communicating. For this reason, we found interesting to look for how companies communicate sustainably.

Purpose: the purpose of this thesis is to answer the question about how companies communicate sustainability through social media. Moreover, the thesis aims to contribute to the existing knowledge.

Method: To answer this question the researchers conducted a multiple case study of three companies that communicate sustainability through the different 4 online platforms studied (Website, Facebook, Instagram, and Twitter).

Results: the main result find by conducting the research is in how companies place the product in order to communicate sustainability, as some of them place it as a protagonist and some others do not.