Documentation of learning through narration and imagery is part of everyday early childhood education. Recently, technology has generated enthusiasm for digital and mobile documentation, where mobility indicates reciprocal communication between home and school using mobile devices. The present paper asks the question of what mobile documentation is "doing" within the boundaries of a teacher's personal and professional public-private timespace-materialities. By focusing on documentation of young children's playful learning shared through social media platforms, I put to work posthuman, feminist materialist theories. What becomes illuminated is that mobile documentation performs within the porous boundaries between a teacher's personal and professional subjectivities. These actions flow between reproduction, generation, and rupture, with hidden labours and affective costs materialised in the liveliness of timestamps, spatialities, and hashtag entanglements. Whilst mobile documentation practices raise ethical questions, they offer potentialities for accessible ways for teachers to operationalise digital doings that offer hopeful, bite-size, and accessible storytelling.