Within our mandate, the ECB is ready to do whatever it takes to preserve the euro. And believe me, it will be enough. — Mario Draghi
With his infamous statement "whatever it takes" on 26 July 2012, ECB President Mario Draghi put an end to speculation. With large asset purchase programmes (APP: asset purchase programmes) the ECB transferred dubious bonds to taxpayer ownership and purchased them with newly printed money.
The extent of the "unconventional monetary policy" can be seen from the chart. The largest sub-programme of the APP is the PSPP, which consists of 90% or almost 2000 billion euros of government bonds (blue). There are also smaller purchase programmes for corporate bonds (CSPP), secured securities (ABSPP) and covered bonds (CBPP3). The APP expired at the end of 2018. In future, the ECB's securities holdings are to be kept at this level. Whether this is sufficient, or whether the ECB will restart its purchase programmes, is matter of speculation.
List of references for the used photo and chart: