The guide includes tools to identify bot accounts on social media, as well as information on the EU, fact-checking resources and tips on how to spot misinformation online.
European elections are due to take place on May 23.
Social media giants Facebook and Twitter have announced their own programmes to target and prevent potential election interference via their platforms.
Mozilla said its EU Elections Toolkit had been created to explain the mechanisms of the internet – including bots and targeted advertising – in “easy-to-understand language” that would help users make “independent, informed decisions”.
“Online manipulation of voter views is a growing problem and many of those voters are essentially defenceless against absorbing disinformation and misleading ideas disguised as ‘facts’,” the company said.
The toolkit also includes guidance for people on how they can improve privacy settings on their accounts and for their web browsing habits.
Mozilla’s Firefox is the world’s third most popular web browser, behind only Google’s Chrome and Apple’s Safari.