Alphabet unit Google won its challenge on Wednesday against a $1.66 billion antitrust fine imposed five years ago for hindering rivals in online search advertising, a week after it lost a much bigger case.

The European Commission, in its 2019 decision, said Google had abused its dominance to prevent websites from using brokers other than its AdSense platform that provided search adverts. The practices it said were illegal took place from 2006 to 2016.

The Luxembourg-based General Court mostly agreed with the European Union competition enforcer's assessments of the case, but annulled the fine.

"The court (...) upheld most of the commission's assessments, but annulled the decision imposing a fine of almost 1.5 billion euros ($1.66 billion) on Google, on the grounds in particular that it had failed to take into account all the relevant circumstances in its assessment of the duration of the contractual clauses that it had found to be unfair," the judges said.

The AdSense fine, one of a trio of fines that have cost Google a total of some $9 billion, was triggered by a complaint from Microsoft in 2010.

Google has said it changed the targeted contracts in 2016 before the Commission's decision.

The company last week lost its final fight against a $2.6 billion fine levied for using its price comparison shopping service to gain an unfair advantage over smaller European rivals.