The Twitter timelines, they are a-changing.

On Wednesday Twitter will start giving the people the option to have the social network algorithmically curate their feeds to show them the top tweets they may have missed since the last time they checked Twitter.

The adoption of an algorithmic feed echoes Facebook's news feed, but Twitter isn't going full-Facebook. Twitter's algorithmic feed is more of a supplement to its traditional reverse-chronological feed than a replacement. For example, Twitter isn't enabling it by default. Instead people will need to opt in to access it, said Twitter VP-Revenue Product Ameet Ranadive.

"Previously when we constructed the user's home timeline, recency was the only factor that determined what content showed up in the home timeline," Mr. Ranadive said. "Now what we're doing is we're taking recency and we're adding relevance to make sure that the best and most timely tweets are what's displayed at the top."

He described the catch-up feed as an extension to the "while you were away" feature Twitter introduced in January 2015.

The new feed will show up atop the river of tweets that logged-in users see when they first open Twitter's app or pull up its site. It will contain about a dozen posts that Twitter's algorithm calculates a person may have missed since they last checked Twitter and would like to see. Those will be limited to tweets from the accounts that a person already follows, Mr. Ranadive said. He originally told Ad Age that the feed would not contain ads, but after this article was published, a Twitter spokeswoman said that he misspoke and that the catch-up feed will contain ads. People will be able to scroll past the catch-up portion to return to their regular reverse-chronological, real-time feed.

To figure out which tweets should reappear in the catch-up feed, Twitter's algorithm will take into consideration which Twitter accounts and types of tweets a person typically interacts with, their interests and any trends among the people they follow, such as whether a lot of those people are tweeting about a certain event, as well as the behavior of Twitter users with similar interests.

Since Twitter is taking into accounts things like the number of retweets or likes a tweet has received when determining what to show in the catch-up feed, some users might be tempted to game its algorithm, promoting a tweet as an ad for example to juice the number of interactions it gets. But the algorithm is designed to reinforce the meritocracy of content on Twitter, according to Mr. Ranadive. It will only rank tweets based on organic engagement, so any retweets or likes that a promoted tweet receives will not factor into that ranking, he said.

"This is a change that essentially makes all content on Twitter created equal," Mr. Ranadive added. "So this is a not pay-to-play platform, unlike our competitors'. The best content, whether it's from a celebrity, another user or a brand, is always going to be what rises to the top."

Although the new feed doesn't offer any immediate, major changes for marketers, anything that gets Twitter's 320 million monthly users to check in more often would expand the reach of Twitter's new First View video ad. First View displays in people's feeds each day when they first open Twitter's app or log into its desktop site.

And considering that brands tend to have large followings and receive a lot of retweets and like for their posts, their unpaid tweets could be more likely to appear in the catch-up feed, extending brands' organic reach and, in turn, potentially leading to more retweets and likes.

"The great news is that the new system prioritizes the best content, in which case marketers who are already making great content have a greater chance of more organic visibility," 360i CEO Sarah Hofstetter said in an email. "So that pretty much aligns with the recommendations we've been giving to clients for years -- it's just that now Twitter is rewarding the better content, organic or paid."

In testing the new algorithmic feed, Mr. Ranadive said, more people ended up interacting with brands' unpaid tweets as well as tweets around live events, when feeds can become especially clogged with an abnormal number of tweets. "We saw that across the board engagement on organic brand content went up significantly," he said. People were also more likely to tweet and retweet others' tweets when they used the algorithmic feed, he added.

BuzzFeed reported Friday that Twitter would be introducing an algorithmic timeline as soon as this week.