Tag:footway=alley
 footway = alley
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An alley is a footway usually located between properties for access to back entrances and/or emergency access. 
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| Group: highways |
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| Status: in use |
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An alley or alleyway is a narrow path usually located between properties which provides access to things such as back gardens, rear entrances, fire exits, and storage areas. Alleys are normally found in urban areas and often run between the rear sides of buildings such as houses and commercial premises. Similar to service=alley for highway=service, a pedestrian foot path can fulfil this role as well, and is a common feature in many countries.
footway=alley can be seen as a way to de-emphasize a highway=footway for pedestrian traffic, similar to how a highway=service sits below highway=residential and other road-tags for motorized traffic.
Tagging
Simply add footway=alley to a highway=footway.
Sometimes access to alleys is restricted by signs or gates; in that case add the proper access=* tags.
When not to use
Not every narrow foot path between properties is a footway=alley, despite being called an alley colloquially. When a foot path provides a de facto, designated, or historical through-route, or is constructed in that role by design, then footway=alley should be omitted.
Common examples of such exceptions are some narrow alleys in medieval city centres, and pedestrian routes between blocks of housing that provide access to playgrounds or small parks enclosed by a block of houses. As a rule of thumb, paths that offer access to the fronts of houses are not a good fit for footway=alley either.
footway=alley indicates a specific type of highway=footway, and should only be used with that tag, i.e. vehicles should not be generally permitted on these.
Background
A recurring source of some strive is the mapping of foot path alleys where these, though publicly accessible, serve an obviously local role — often limited to rear access of the properties along that path. Some mappers choose to map such alleys with access=private, but this goes against the good practice of mapping what's actually on the ground, rather than what locals desire it to be. Whatever the mapper's (or local inhabitant's) standpoint, these alleys exist, and some mappers prefer to map them along with any other ways in the area. Removing such paths is problematic too, because it may simply lead to other mappers reintroducing them.
As a further refinement of highway=footway, this tag can help solve this issue by providing a way for renderers, routers, and other data consumers to treat these in a manner appropriate to the function of these alleys in the spirit of highway=service and service=alley, while not outright ignoring them or blocking their use. It also helps communicate to other mappers and users alike that the alley-like function of the path is acknowledged.
Tips for renderers
Interpreting footway=* values can provide a way to visually declutter a map at lower zoom levels by de-emphasising ways tagged with tags like footway=alley, or not rendering them until zoomed in further.
Tips for routers
While access to this such alleys is not necessarily restricted, on the whole they tend to be less desirable for routing foot traffic or dismounted cyclists. Routers can use the presence footway=alley to award a small penalty to these (similar to how motorized traffic avoids highway=service for through-traffic), thus avoiding them unless they provide a significant short-cut.