Most surveys of people who inject drugs (PWID) fail to represent the full population of PWID, because usual recruitment methods do not achieve geographic and sociodemographic diversity. People of color, people residing in rural and/or harm reduction-deprived areas, and people who rarely connect with social services are the least surveyed and understood PWID populations. Online-based recruitment and surveys may better reach these hidden PWID populations than standard venue-based recruitment. As technology use and internet access become more ubiquitous, even for unstably housed populations, research using online-based recruitment and survey techniques are growing in the substance use field. These methods hold promise for obtaining larger and more diverse PWID samples, but there are no standards for using online recruitment and survey administration methods to reach large populations of PWID vulnerable to overdose and other threats. Best practices are needed to maximize data quality, prevent fraudulent responses, and minimize selection biases. The HOME (Harm reduction services Offered through Mail-delivery Expansion) study recruits and enrolls a national, online-recruited, longitudinal cohort of 1233 PWID and follows them for 18 months. Key objectives are to assess prior harm reduction utilization and future uptake of mail-based harm reduction services and retention in these services. We describe our online data collection protocol, including recruitment approaches, detecting fraud, maximizing data quality, and participant retention throughout follow-up. These strategies can inform subsequent large-scale, nationwide efforts that recruit PWID through the internet.