Dynamic windows based on the reversible electrodeposition of metals are the promising alternatives to those based on other technologies such as electrochromic materials. In this article, we use spectroelectrochemistry to study Cu and Pb electrodeposition and dissolution as related to dynamic window electrolytes. The presence of Cl- in the aqueous electrolyte accelerates the deposition and dissolution processes, and leads to the formation of Cu-Cl equilibria that evolve during electrode cycling. The electrolyte only supports reversible metal deposition after cycling, a process known as electrolytic conditioning. We demonstrate that the conditioning process increases the concentration of Cu-Cl complexes in the electrolyte, which facilitates reversible and kinetically facile electrodeposition. The conditioned electrolyte enables the construction of 25 cm(2) dynamic windows harnessing reversible metal electrodeposition that exhibit uniform tinting, minute-order switching times, and high optical contrast. Understanding electrolyte dynamics is key to constructing 25 cm(2) dynamics windows with electronically controlled transparency based on the reversible metal electrodeposition of Pb and Cu. [GRAPHICS] .