Carolyn Everson (VP, Global Marketing Solutions, Facebook)Video: Connecting People, Reshaping Marketing seminar, Advertising Week New York 2017, PlayStation East Stage, PlayStation Theater, New York, USA - 25 Sep 2017

Instagram’s swelling fan base shows no signs of stopping.

According to parent company Facebook, the photo-sharing network has swelled another 100 million monthly users in recent months. Carolyn Everson, Facebook’s vice president of global marketing solutions, revealed the gain at a New York City Advertising Week event on Monday. After disclosing 700 million monthly active users in April, Instagram now counts 800 million people pushing images and video across the network every month. More than half use the service every day, with daily Instagrammers numbering 500 million.

The news may be a bitter pill for chief competitor Snap Inc., which logged 173 million daily users as of last month.

Facebook tried to acquire Snapchat for $3 billion in 2013 — the year after it purchased Instagram for $1 billion. Snap chief executive officer and founder Evan Spiegel turned it down, and ever since, the social giant has been quick to crib Snapchat’s most-innovative features.

“Stories,” in particular, is key to both photo-sharing networks’ pursuit of the fashion and beauty sectors. Snapchat representatives describe the feature in storytelling terms — a feed of images and video that lives for 24 hours — while Instagram’s Stories delivers more of “a narrative” than a self-destructing photo to a friend or limited group.

The distinction matters, especially to the company’s fashion ambitions. Some designers — like Marc Jacobs, Burberry, Louis Vuitton, Rebecca Minkoff, Prabal Gurung and others — have used Snapchat to pull the curtain back, offering personal behind-the-scenes glimpses or branded feeds.

Others, however, don’t see Snapchat as a one-size-fits-all social platform that could work for everyone. Jodie Chan, director of Altuzarra’s marketing and communications, viewed the raw-style of sharing as an ill-fit for her brand and target clientele, and, she added, the latest “numbers seem in line with [that] sentiment.”

Instagram’s own Stories rollout didn’t help matters. Just after the rival debuted the copycat feature, Snapchat’s percentage growth stalled: In the third quarter of 2016, its growth clocked in at a mere 7 percent. At the time, the company had 153 million daily active users; nearly one year later, it has only added 20 million more, a fraction of Instagram’s growth.

Technology insiders believe that anxiety rides high within Snap’s walls, with employees fretting over Instagram’s looming shadow. If true, it’s not hard to see why. Instagram’s pipeline to Facebook means it has direct integration to its 2-billion-user platform, and the “Insta-Model” craze — which launches the rival platform’s popular fashion personalities into the modeling stratosphere — has proved irresistible to advertisers, 2 million of which have now joined it ranks.

But some caution not to count Snapchat out yet.

“There is still reason to be optimistic,” said John Koetsier, a mobile economist at marketing firm Tune. “Instagram and Snapchat are two very different things, and occupy different spaces in kids’ lives.” He believes Snapchat works for “live or almost-live” experiences, and Instagram — which is “difficult for two-way communication” — is more about curation.

Citi Research offered another sign of hope: According to its August 2017 report, Instagram may have more users, but people on Snapchat spend more time on the platform — on average, they spent more than 30 minutes engaged in the app. And, according to Citi analysts Mark May and Caleb Siegel, “The two most important metrics for a social media platform are, arguably, the number of active users and the average time spent by those users.” Snapchat has half the equation nailed down. Time to focus on that pesky other half.

Neither Snapchat nor Instagram responded immediately to requests for comment.