The short answer is: often, but not always. Many urban planter boxes designed for outdoor use—especially commercial street planters, balcony troughs, and modular city gardening systems—come with drainage holes already built in. Manufacturers know that container plants need a way for excess water to escape, so they commonly pre-drill one or more holes, add a perforated base, or provide knock-out plugs that you remove before planting.
That said, “urban planter box” is a broad category. Decorative indoor-style boxes, lightweight budget models, and some self-watering or sealed architectural planters may arrive without open drainage. They might have a reservoir, a plug, or no holes at all to protect floors and patios. So before you buy, check the product specifications and photos. Look for phrases such as “pre-drilled drainage,” “drainage holes,” “knock-outs,” “overflow,” or “removable plugs.” If the listing is vague, ask the seller.
If your planter has no drainage holes, you can usually add them. Drill from the inside out to avoid chipping the finish, use a bit suitable for the material, and make several holes across the base. For metal or plastic, take care with sharp edges; for wood, seal the cut edges to slow rot. If drilling is not possible, choose a different planter or use it as a cachepot with a properly drained inner pot.
Drainage matters because urban planters can fill up quickly in rain, and waterlogged soil starves roots of oxygen and encourages root rot. Drainage holes also help flush excess salts from fertilizer. Place the planter so holes are not blocked by a saucer or pavement, or raise it on feet. In windy, exposed city sites, good drainage and the right soil mix also help keep the planter from becoming overly heavy.
In short: urban planter boxes frequently come with drainage holes, but you should always verify the specific model. If holes are missing, plan to add them or adjust your planting setup.