For those with marginalized identities, social media may offer opportunities for identity exploration and affirmation but may also pose challenges of context collapse, wherein the presence of multiple audiences makes identity-related posting awkward or dangerous. To probe short-term longitudinal patterns, 337 LGBTQ+ 15- to 22-year-olds completed six weekly surveys during Pride Month. As hypothesized, identity exploration was associated with self-reported frequency, positivity, and authenticity of youths’ LGBTQ+ self-presentations online, primarily among those who, on average, rated their online audiences as less heterogeneous (i.e., perceived less context collapse). Consistent with the self-effects model, positivity of self-presentations predicted increases in self-acceptance and self-esteem, with the latter association stronger for those who, on average, received more supportive feedback. In contrast, frequency and authenticity of self-presentations did not predict self-acceptance and self-esteem.