BACKGROUND: The continual diversification of new psychoactive substances (NPS) circumventing legislation creates a public health and law enforcement challenge, and one particularly challenged by availability on Hidden Web cryptomarkets.

METHODS: This is the first study of its kind which aimed to explore and characterise cryptomarket forum members' views and perspectives on NPS vendors and products within the context of Hidden Web community dynamics. An internal site search was conducted on two cryptomarkets popular with NPS vendors and hosting fora; Alphabay and Valhalla, using the search terms of 40 popular NPS in the seven categories of stimulant/cathinone; GABA activating; hallucinogen, dissociative, cannabinoid, opioid and other/unspecified/uncategorised NPS. 852 identified threads relating to the discussion of these NPS were generated. Following exclusion of duplicates, 138 threads remained. The Empirical Phenomenological Psychological method of data analysis was applied. Four themes and 32 categories emerged.

RESULTS: 120 vendors selling NPS were visible on Alphabay, and 21 on Valhalla. Themes were 'NPS Cryptomarkets and Crypto-community interest in NPS'; 'Motives for NPS use'; 'Indigenous Crypto Community Harm Reduction'; and 'Cryptomarket Characteristics underpinning NPS trafficking', with two higher levels of abstraction centring on 'NPS vendor reputation' and 'NPS transactioning for personal use'. NPS cryptomarket characteristics centred on generation of trust, honesty and excellent service. Users appeared well informed, with harm reduction and vendor information exchange central to NPS market dynamics. GABA activating substances appeared most popular in terms of buyer interest on cryptomarkets. Interest in sourcing 'old favorite' stimulant and dissociative NPS was evident, alongside the sequential and concurrent poly use of NPS, and use of NPS with illicit drugs such as MDMA.

CONCLUSION: Continued monitoring of new trends in NPS within Surface Web and cryptomarkets are warranted. A particular focus on the rising market in prescribed benzodiazepine and Z-hypnotic drugs should be included.