Google announced on Twitter. They are about to roll out a broad core algorithm update later today. Here is a screenshot of the same.

Google SearchLiaison

Google usually makes one or more updates each day to enrich its results. Most of these updates have only minor effects that go unnoticed. However, they pre-announce an update only when it’s something big. 

The objective of the broad core updates is to present the searches relevant, fresh, and authoritative content. Broad core updates have a wide and noticeable effect. Most of the sites see fluctuations in their rankings. Google had previously announced that the sites that suffer a drop in their ranking haven’t violated any webmaster guidelines. The shuffle in the ranking is a result of Google’s efforts to make more relevant content accessible to a searcher. 

The best way of coping with a core update is to update your site’s content. Ensure that your site contains original content, which is comprehensive and provides insightful information to the searchers. Make sure you have no plagiarized content. It should be free from any factual and grammatical errors. Your content should not contain excessive ads that can distract visitors from the main content.