Purpose: In response to concerns about fake news (Allcott et al., 2019) and polarization (Wollebaek et al., 2019), youth media literacy interventions have emerged to teach strategies for assessing credibility of online news (McGrew et al., 2018) and producing media to mobilize others for civic goals (Kahne et al., 2016). However, in light of evidence that practices learned in classroom contexts do not reliably translate to the context of sharing social media (Middaugh, 2018), this study aims to provide a better understanding of youth social media practices needed to design meaningful and relevant educational experiences. Design/methodology/approach: Semistructured interviews with a think-aloud component were conducted with a diverse sample of 18 California youth (15-24) to learn about factors that guide behavior as they access, endorse, share, comment and produce civic media. Findings: Findings suggest a shift toward reliance on incidental exposure and noninstitutional sources when accessing information and a tendency toward endorsement and circulation of posts (vs producing original posts) when engaging with civic issues on social media. As participants engaged in these practices, they not only applied judgments of credibility and civic impact but also concerned for personal relevance, relational considerations and fit with internet culture. Originality/value: The authors recommend moving beyond models that reflect linear processes of effortful search, credibility analysis and production. Instead, the authors propose a new dynamic model of civic media literacy in which youth apply judgments of credibility, relational considerations, relevance to lived experience, civic impact and fit with internet culture as they receive, endorse, share, comment on and produce media in a nonlinear fashion.