Jail cells in Westerns always have a window to an alley where pals of the prisoner can toss notes or guns through. How accurate is that?
Jails were as different as the towns where they existed. Some were built of bricks and mortar, while others were made of adobe, stone or wood. Many didn’t have windows.
Some towns didn’t even have jails. Wickenburg, Arizona, chained its prisoners to a jail tree. These were usually drunks who were released when they sobered up.
I’m sure some cells had windows that opened into alleys, but for the most part, that is a Hollywood invention. As you noted, the Westerns always had a window in back to help with a jailbreak—the script called for a crony to either slip the prisoner a pistol or tie a rope around a jail bar, take a dally around his saddle horn and yank it out.
In reality, cell windows were just large enough to create a draft during the heat of summer; during cold weather, they could be easily covered.