There are several synonyms for the phrase "are common" that you can use to make your writing sound more diverse and engaging. Some options include "are abundant," "are widespread," "are ubiquitous," "are prevalent," "are popular," "are typical," "are ubiquitous," and "are customary." These synonyms can be used in various contexts to describe the frequency or common occurrence of something. For example, you could say, "Fast food restaurants are prevalent in urban areas," or "Credentials are customary for job applicants in many industries." Remember, using synonyms in your writing can help you avoid repetition and keep your readers engaged.