TLS 1.3 was defined in RFC 8446 in August 2018.[7] and updated with RFC 9846 in July 2026. It is based on the earlier TLS 1.2 specification.

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Network Security Services (NSS), the cryptography library developed by Mozilla and used by its web browser Firefox, enabled TLS 1.3 by default in February 2017.[61]

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In September 2018, the popular OpenSSL project released version 1.1.1 of its library, in which support for TLS 1.3 was „the headline new feature“.[74]