Which dialect of Middle English did Geoffrey Chaucer use?

Geoffrey Chaucer, who was born and lived in London, wrote in a dialect that was basically East Midland.1

While he utilized this dialect for his own literary works, it is worth noting that he was also a skilled linguist who read Latin and spoke French and Italian. Furthermore, in his masterpiece, The Canterbury Tales, he demonstrated an awareness of regional speech patterns; for instance, in The Reeve’s Tale, he famously employed a broad Northern dialect for specific characters to achieve a comic effect.12