The ECB's dovish pivot -- which follows its recently released strategy review -- at a time when many peers are mulling exiting pandemic-era stimulus is expected to keep the single currency under pressure.
"A lot of what happens today with the ECB hinges on just how much of an inflation-averaging central bank Lagarde and the press conference portray them as," said Stephen Gallo, European head of FX strategy at BMO Capital Markets, speaking before the ECB decision but ahead of the news conference.
"The more they look willing to tolerate a significantly higher rate of inflation, the more negative it will be for the euro, bullish for commodity and emerging market currencies versus the euro."
He added, however, that much hinged on how much consensus there was within the governing council to extend bond-buying once pandemic-time stimulus expires in March.
Elsewhere, growth-focused currencies such as the Australian dollar gained as a global risk sell-off abated further.
The U.S. dollar index and the yen which rose earlier this week to the highest since early-April and end-May respectively, retreated as strong earnings lifted stock markets and bond yields, and induced investors to trickle out of the safe-haven assets they had piled into.
They also bought back into cryptocurrencies, with bitcoin rising further above the $30,000 mark, especially after Tesla CEO Elon Musk said the company would "most likely" resume accepting bitcoin for payment.
The dollar index =USD , which measures the currency against six major peers, slipped to 92.75 after pulling back from a 3-1/2 month high of 93.194 touched on Wednesday.
The yen, another safe-haven, was at 129.81 per euro, from an almost four-month top of 128.610 hit this week, and was flat versus the dollar at 110.3 yen.
The Australian dollar changed hands at $0.738, from an eight-month low of $0.72895 the previous day, despite half the Australian population being under COVID lockdowns.
The gains in higher-risk assets come after robust company earnings lifted Wall Street and European bourses, allowing investors to look past concerns that the Delta Covid-19 variant would dampen the economic recovery.
"The consensus is that (the Delta strain) does not pose an immediate risk to the recovery," delaying reopening by three months at the most as countries ramp up vaccination drives," National Australia Bank analyst Tapas Strickland told clients.
Sterling firmed to $1.3768, recovering from 5-1/2 month troughs while in cryptocurrencies, bitcoin slipped into negative territory after Wednesday's 7.9% jump - the biggest since mid-June -- to trade below $32,000.
(additional reporting by Tommy Wilkes Editing by Elaine Hardcastle and Bernadette Baum) ((firstname.lastname@example.org; Reuters Messaging: email@example.com))