It is held by the Guggenheim Museum in New York City. In subject matter, Before the Mirror catches a courtesan about to disrobe before a mirror. Manet consistently drew upon this motif of undress as a means of rendering the truth of modern life, as a spontaneous imagining of a moment in passing.

The artist adopts vigorous brushstrokes in his work to accentuate this idea of transition or immediacy, giving the painting a feeling of movement and time. The effect of such a brushstroke and the delicate blending of colour emphasises an improvised quality, reflecting a happenstance moment in pursuit of authenticity.

Furthermore, the woman in the painting stands admiring her reflection as she undoes her corset. Framed from behind, it provokes an intimate and almost voyeuristic capture of the woman quietly contemplating herself in her reflection. Manet's portraits of courtesans broadly aligned with his endeavour to capture and record social life. The style and content reminds many of Degas and Renoir.

Elsewhere, Manet painted street performers, barmaids, members of high society, low society, races and other Parisian types that were subjects of contemporary French literature.

Manet is perhaps best known for his paintings of modern Parisian life, adopting an approach to his subject which mirrored literary notions of the flâneur (stroller) who sauntered the streets observing society. Manet came from bourgeois beginnings, born into a wealthy upper-class family that expected him to pursue a career in law.

Instead, Manet led a bohemian lifestyle as a painter, training under the traditional artist Thomas Couture and heavily influenced by the Realist painter Gustave Courbet. Although Manet began his career within their footsteps, he soon began subverting realism in favour of attention to transitory and temporal detail in light and shade. It is this transition between Realism and Impressionism for which Manet became famous. Among his admirers at the end of the nineteenth-century included Claude Monet and Frédéric Bazille, who proclaimed him an avant-garde master.

He attracted significant controversy in his time not only for his style—which was considered by some as "unfinished" due to its use of colour patches and shallow volume—but also for his choice of subject matter; Manet frequently depicted courtesans and the female nude with an honesty instead of attending to their "ideal" form. Among such controversial artworks was Olympia, a painting of a nude prostitute which shocked the Paris Salon in 1863. This current painting, Before the Mirror, attracted similar controversy.