For an introduction to IBOR transition, read this article
In September 2018, the working group on euro risk-free rates, which was set up by the ECB, together with the Financial Services and Markets Authority, the European Securities and Markets Authority and the European Commission, recommended that the euro short-term rate (€STR) replace the euro overnight index average (EONIA) as the new euro risk-free rate.
€STR is a daily overnight benchmark rate developed by the European Central Bank (ECB) based on the previous day’s overnight unsecured fixed rate deposit transactions in euro conducted with financial counterparties and reported by banks to the European System of Central Banks for statistical purposes. The ECB has been publishing €STR since 2 October 2019.
The calculation methodology for EONIA has been modified on 2 October 2019. EONIA’s daily rate is now equal to €STR’s daily rate plus 8.5 basis points (0.0085%), a spread calculated by the ECB as the difference between EONIA and pre-€STR for the one year period up to 16 April 2019.