What is a Meta description?
Meta descriptions are HTML attributes that provide concise summaries of webpages. They are between one sentence to a short paragraph and appear underneath the blue clickable links in a search engine results page (SERP). Google might pull Meta description text from other areas on your page.
Meta descriptions can be any length, but Google generally truncates snippets ~ 300 characters (this limit increased in December 2017). It's best to keep Meta descriptions long enough that they're sufficiently descriptive, so we recommend descriptions between 50–300 characters.
How this will affect SEO?
A. It changes how marketers should write and optimize the Meta description.
You’ll going to be writing a little bit differently because you have more space. You’ll going to be trying to entice people to click, there's a good chance that Google will rank you higher, even if you are actually sort of sacrificing clicks by helping the searcher get the answer they need in the search result.
B. It may impact click-through rate.
You’ll be looking at Jumpshot data over the next few months and year ahead. There are two likely ways they could do it. Probably negatively, meaning fewer clicks on less complex queries. But conversely, possible it will get more clicks on some more complex queries, because people are more enticed by the longer description.
What should SEOs do?
The first thing, you should probably already have your most important landing pages by search traffic, the ones that receive the most search traffic on your website, organic search. Then you would go and reoptimize those Meta descriptions for the longer limits.
The second thing, you will do is: if you have internal processes or your CMS has rules around how long you can make a Meta description tag, you're going to have to update those probably from the old limit in the range of 160 to 180 to the new one 230 to 320.
Good luck with your new Meta descriptions!