Social media content includes an unprecedented number of personal documents reflecting our time. Few countries or regions have established legal grounds for securing long-term access to these documents, while paper-based publications have been exhaustively accumulated under legal deposit systems. However, archiving social media through national libraries, as a sort of state intervention, could bring about chilling effects on free speech in unexpected ways. The article aims to present empirical data of public concerns concerning social media content, focusing on Twitter’s public tweets archived by third parties, through two questionnaire surveys involving university students (Research I) and the public (Research II). The surveys were designed based on three settings: researchers, organisations to which the respondents belong and the National Diet Library in Japan. Consequently, approximately 30% and 47% of the respondents in Research I ( n = 197) and II ( n = 728), respectively, disagreed with any hypothetical scenario. An ordered logistic analysis to reveal the inter-relations of variables suggests the existence of other factors; thus, neither variables related to Twitter/Internet use nor demographic variables influenced people’s perceptions of the archival issue. While protecting privacy rights and copyrights was the primary reason for disagreements regarding third-party archival of tweets, many respondents intuitively displayed a negative reaction without any specific reason. Those who question its value and feel uncomfortable with an authoritative intervention were also identified. To nurture acceptant attitudes, advocating the archival of personal documents and adopting more restrictive archival procedures like taking down posts and anonymisation, public debates on the intervention of public bodies and demonstration of archival values should be considered.
