Alice Stoehr’s review published on Letterboxd :
How the hell do I begin talking about this? Usually movies will suggest obvious paths along which I can start writing, gradually getting deeper, eventually broaching their inner recesses. But Boyhood is a maze of such paths, looping and intertwining, each passageway leading to another. Every single instant in the movie is a thematic nerve ending. They point back to the film's past, then toward its future; they bump against parallel moments in my own life or my own memories of the time periods they capture. Watching this, to be frank, was a tad overwhelming, and the more I think about it the more awed and devastated it leaves me.
Awed, I should explain, because of the film's expansive subject matter and the thoroughness with which it's charted. Devastated because change and uncertainty are constants in life, and both of them pervade Boyhood. Shot with year-long time delays, Mason's life is a process, much like the erosion of a cliff face or the rotting of fruit. A 6-year-old squirreling homework away in his backpack becomes a Vonnegut-reading middle schooler, then suddenly he's a teenager passive-aggressively snapping arty photos at a football game, and just as quickly the movie's over. Whoever he'll grow into next lies in the unknowable future.
But because life is a process, Mason will always bear the imprints of the experiences that sculpted him. They accumulate across the film, most of them seemingly unremarkable yet still wry and observant. (They only strike a couple false notes, once during a beer-fueled "camp-out" and later during an episode with a Mexican handyman.) These fragments recount small details of Mason's burgeoning maturity as well as formative relationships with his mom, older sister, and "cool" absentee dad, each of whom undergo experiences of their own within the film's year-eliding cuts. Linklater compacts so much, in the form of both onscreen story and gap-filling implication, into these modest narrative snippets.
He crams every vignette full of questions, the most prominent (and poignant) of which include "What makes us who we are?" and "Who should we want to become?" Every development in the film signifies not only growth but loss, too—a foreclosure on infinite possibility. Dad gets remarried and sells his sports car. Mom gets thrice divorced and sells her house. Mason breaks up with his girlfriend and sets off for college. He may become a professional photographer, or he may not. I really hope he does, but to my chagrin Boyhood's denouement is thick with ambiguity, just like the ending of each Before movie. All that can be known for certain is what's already been lost to the past.