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Utility location is the process of identifying and labeling public utility mains that are underground. These mains may include lines for telecommunication, electricity distribution, natural gas, cable television, fiber optics, traffic lights, street lights, storm drains, water mains, and wastewater pipes. In some locations, major oil and gas pipelines, national defense communication lines, mass transit, rail, and road tunnels also compete for space underground.

Public utility systems are often run underground—some by the very nature of their function, others for convenience or aesthetics. In the United States, it is estimated that subsurface lines amount to over in total. Before digging, local governments often require that the underground systems' locations be denoted and approved, if it is to be in the public right of way. Pipeline markers, signs, or other indicators may or not be visible to warn of the presence of underground utilities. For various reasons, including security, the precise location of the utilities may not be indicated. The only way an excavator can know the precise location, number, and types of utilities is to contact the underground utilities coordinator, and request that the locations be marked. In most jurisdictions, there is no charge for this service, but advance notification is a legal requirement. In the UK, to follow HSG47 and PAS128 guidelines, it is recommended that a Desktop Utility Search is carried out. A Utility Search, also known as a C2 Utility Search or PAS128 (D) utility search, is the initial step in identifying utility asset owners and locating their buried and overhead assets and apparatus. A Utility Search is essential for development projects as it provides valuable insight into the presence and location of underground and overhead utility assets. As well as providing a understanding of the networks within the vicinity of a site, this information can help to prevent accidents, disruptions, and costly delays during construction.

Because of the many different types of materials that go into manufacturing each of the different types of underground lines, different detection and location methods must be used. The two general methods are called passive locating and active locating. Passive locating uses signals that occur naturally on some utility lines. This method often fails to locate 60% or so of utility lines, and misidentifying utilities is an associated risk. Active locating, on the other hand, is more accurate. It makes use of signals that the locators generate through a transmitter. Then, with the help of a receiver, locators can trace as well as identify what type of utility line lies underground. The active method is the most suitable for locating conductive metal pipes and cables. This process often involves using a piece of electromagnetic equipment, consisting of a transmitter and a receiver. For other types of pipe such as plastic or concrete, a metallic tracer wire or conductive foil (detectable tape) may be buried alongside or immediately above the pipe, to aid in locating it. In the absence of such a conductive tracer, other types of radiolocation or modern ground penetrating radar must be used. Location by these technical means is necessary because maps often lack the pinpoint precision needed to ensure proper clearance. In older cities, it is especially a problem since maps may be very inaccurate, or may be missing entirely. A few utilities are permanently marked with short posts or bollards, mainly for lines carrying petroleum products. This may be done because of venting requirements, and also serves to indicate the location of underground facilities that are especially hazardous if disturbed. , utility locators depend primarily on three types of utility locating equipment to do their job, including GPR, electromagnetic profiling locators, and radio frequency pipe locators. These tools are produced by a number of manufacturers, and are widely available throughout the world. Some of the large manufacturers include Leica, RIDGID, and Schonstedt. With advances in technology, these tools continue to improve, and locators in the field are able to be more accurate. Many utilities are now mapped out on GIS mapping services like ESRI, which improves both accuracy and process transparency. Some of the current locate wands are able to relay their information and sync up with GIS systems to expand and correct the information on the map, which helps to update the map very rapidly.

In the US, Canada, Australia, and New Zealand, many large locate companies handle millions of tickets every dig season, and need a way of managing these tickets and sending them through to a unified call center (for example, Underground Service Alert). The Common Ground Alliance (CGA) publishes the Damage Information Reporting Tool (DIRT report) every year, which gives a fuller picture of the effects of utility locating throughout North America. In recent years, DIRT has demonstrated a trend of greater excavation damage incidents over time. This report does not contain every single incident, as stakeholders voluntarily submit underground damages and near miss reports, but it is the most complete repository of utility damages anywhere in the world. Utility Locators and other stakeholders depend on data like this to learn about risks and to justify continued investment in the industry. Industry leaders in damage prevention like the Common Ground Alliance and IR Saving Lives are the biggest promoters of utility locating, and encourage other stakeholders to take utility locating seriously. The CGA also has published a paper called "Insights into Improving the Delivery of Accurate, On Time Locates", which has expert information on how to improve the locating industry in the US and Canada (not to be confused with the Canadian Common Ground Alliance (CCGA), a companion organization to CGA in Canada). Other technologies and equipment are identified in Technology Reports by CGA and in a major study by the Pipeline and Hazardous Materials Safety Administration in 2017 entitled A Study on Improving Damage Prevention Technology.

Utility color codes are used to identify existing underground utilities in construction areas, to protect them from damage during excavation. Colored lines, flags, or both are used to mark the location and denote the type of underground utility. A special type of spray paint dispenser, which works when the can is upside down, is used to mark lines, often in a fluorescent color. On flags, a logo often identifies the company or municipal utility which the lines belong to. Flags may also be an advertisement for a company which has installed an irrigation system for lawns or gardens. In this case, each sprinkler head is usually marked, so that landscaping crews will not cover or bury them with soil or sod, or damage them with tractors or other construction equipment while digging holes for trees, shrubs, or other large plants or fenceposts. This is also important because a vehicle (tractor, truck, or otherwise) can break a sprinkler or the hard PVC pipe or joint it is mounted on, simply by driving over it, particularly on newly moved soil which is uncompacted and therefore unsupportive of such weight.