Communication is indispensable for institutions in regaining trust and credibility among citizens. In this context, transparency management and the promotion of citizen participation online are essential. After December 2015, when the Spanish transparency law 19/2013 was fully in force at the local level, all local municipalities were required to show all the public information on their websites published in a clear and understandable way. This requirement turns the Spanish local administrations into an interesting case study to assess efforts to improve their relationships with their citizens; hence this research aims to measure the Spanish transparency level on public information and participation. For that purpose, a set of indicators were used to analyze the content of those websites that corresponded to a representative sample of municipalities with 10,000 or more inhabitants (N=394). Findings pointed to a very low transparency level and major deficiencies related to online engagement with resources that are required by law.