Begun in January 2011 amid mass demonstrations in downtown Cairo, “Tahrir: Liberation Square” had its official premiere scarcely six months later at the Locarno Film Festival in Switzerland. That makes it a hot document as far as movies go, recording events with ramifications yet unknown to Egyptians or the rest of the world.

But far from imposing clarity on the historic gatherings, “Tahrir” embraces the thrill and uncertainty of popular action. In some ways resembling old-fashioned vérité, Stefano Savona’s chronicle aims to plunge you into the crowds and clamor. Updates trickle in — is President Hosni Mubarak sending thugs? has he resigned? — just as someone on the ground might learn them, by hook or by crook, but usually by cellphone. This modern revolution was posted on Facebook, and we hear quotations from not only the Tunisian poet Abul-Qasim al-Shabi but also (in English) whichever gym teacher first said “No pain, no gain.”

The film tacks between chanting throngs and earnest individuals voicing hopes and grievances, debating constitutional and religious outcomes, or simply reacting. Though a young man in a checkered scarf becomes an unofficial commentator and an older gentleman is given free rein to deliver a monologue about youth and change, “Tahrir” is a group portrait. Mr. Savona, formerly a student of archaeology and anthropology, focuses on the homemade rhythms of strangers brought close together, the words of their call-and-response and the felt duration of watching and waiting.

Idealism, pride and solidarity carry the day and the night, which flow into one another without explanatory titles or voice-over. The mood and presentation are a conscious choice, contrasting with the succinct HBO documentary “In Tahrir Square” (which sets grim stakes by opening with torture footage) or the analysis and exposé of the film “Tahrir 2011.” The sociably close camerawork and vivid HD photography, which gains a kind of humid vibrance by night, foster the sense of being in the moment.