Facebook's and Snapchat’s self-serve ad-buying tools estimate the size of advertisers’ target audiences. Here is how those sizes stack up.

Perception plays a big role when digital platforms jockey for brand ad dollars. Notions like “everyone’s on Facebook … except for high schoolers, who are all on Snapchat … but everyone’s leaving Snapchat for Instagram” can make marketers pause when deciding how to map out their budget allocations.

Perceptions about the platforms’ audience size and demographics can be fact-checked — to an extent. Facebook’s and Snapchat’s self-serve ad-buying tools let advertisers configure the audiences they want to reach by location, age, interests and behaviors and provide estimates of how many people are in a given audience group.

Want to know how many 25-year-old and older moms in Atlanta are on Facebook and how that compares with Instagram and Snapchat? Curious if you can reach more 13- to 17-year-olds in the United Kingdom through Snapchat or through Instagram? Unsure whether targeting an ad to 18- to 20-year-olds in Canada in Instagram’s Stories feed would sacrifice too much reach compared to slotting it in Instagram’s main feed?

Those answers are all there, though answers is likely too strong a word. “Indications” may be more appropriate, because the numbers may be misleading given how Facebook and Snapchat measure their audiences. For a fuller discussion of their respective methodologies, I’ve listed several caveats at the bottom of this article.

The numbers are also moving targets. Because both Facebook and Snapchat update their estimates daily and base those estimates on recent usage over a rolling period of time, the potential reach for any given audience can and often does change from one day to the next. And the platform-provided reach estimates don’t include the potential “viral reach” generated by people sharing an ad through Facebook’s share button, Instagram’s commenting system or Snapchat’s private messages.

How the platforms’ audiences measure up
Given that Facebook’s and Snapchat’s ad-buying tools offer the platforms’ own counts of their reach among specific audiences, businesses can use these pseudo-official counts when evaluating how to allocate their ad dollars, as well as when strategizing which social networks or social ad formats to prioritize in their next campaign. The estimates are also useful when assessing the rivalries of Facebook versus Snapchat and Instagram versus Snapchat. How much of a hold does Snapchat currently have over younger users? To what extent is Facebook the sole domain of older users? How are millennials’ attentions split?

To the latter end, I’ve compiled several samples that are plotted below to show how audience sizes compare across Facebook, Instagram and Snapchat for various age groups, from 13- to 17-year-olds to the 35-and-older demographic, segmented by country. (Twitter and Pinterest do not support age-based targeting, so they are not included here).

I’ve broken the stats down into four placement categories:

Facebook: This represents ads shown to people on Facebook’s own site and app, but not Instagram, Messenger or its Audience Network ad network of third-party sites and apps.
Instagram Feed: This is limited to people shown an ad while scrolling through Instagram’s main, traditional feed.
Instagram Stories: This captures the number of people who would be eligible to see an ad within Instagram’s Stories feed.
Snapchat: This only includes the number of people who could see a standard, vertical video Snap Ad, not those who could be exposed to a Sponsored Lens or Geofilter. It’s a measure of Snapchat users that view Stories, Shows and Discover channels but does not include people who may only use the private messaging part of Snapchat.
All of these numbers are estimates based on usage over roughly the past month and are updated daily. Facebook only presents a single number for its own and Instagram’s audience sizes, so that’s what I’ve included in the charts. Snapchat offers a range. Assuming that Facebook would opt to present the biggest number possible, I’ve decided to use the high end of Snapchat’s range for the comparisons.

The countries I’ve included represent the seven largest countries by media spend, according to eMarketer, that advertisers can target across Facebook, Instagram and Snapchat: the United States, the United Kingdom, Germany, Brazil, France, Australia and Canada. Given that the numbers represent recent usage and count travelers among a country’s audience, the numbers are susceptible to some inflation because they factor in usage during August, typically a busy travel month.

The age ranges are based on Snapchat’s available categories; unlike Facebook’s self-serve tool, Snapchat’s does not enable specifying custom age ranges but instead provides five preset ranges.

Because of all the caveats mentioned above, and especially those listed at the end of this article, I’ve decided not to include the raw numbers in the charts below. As I wrote above, these stats aren’t answers but indications.

All ages

Instagram’s Stories product may be larger than all of Snapchat from an overall daily audience perspective, but this chart shows that Snapchat offers a larger reach in five of the seven countries, including the US, the UK and France, for advertisers producing full-screen vertical videos. Of course, Instagram offers more eyeballs in its main feed than Snapchat in all but one country. And Facebook reaches significantly more people than either Instagram or Snapchat.

13- to 17-year-olds

If you’re an advertiser looking to reach high schoolers, Snapchat remains the place to be by a large margin. Visual apps like Snapchat and Instagram appear to especially appeal to this demographic. Not only is Snapchat exceedingly popular, but Instagram closely rivals its parent company, Facebook, in all countries except Brazil.

18- to 24-year-olds

Snapchat’s appeal continues into the college-age crowd. While the chart above shows estimates for 18- to 24-year-olds, among 18- to 20-year-olds, Snapchat offers more reach than Facebook and Instagram in the US, the UK, France and Canada. It also edges out Instagram in Australia and Canada. That could indicate that as Snapchat’s audience gets older, it is — and may continue to be — able to keep that audience on its platform, even as those users are more widely exposed to other social networks like Facebook and Instagram.

While Snapchat wins over high school and college students, as people age into adulthood, Facebook and Instagram begin to take over. Facebook and Instagram’s main feed offer more reach among 21- to 24-year-olds than Snapchat in six of the seven countries. That may have to do with people joining the workforce and befriending older colleagues who may be more likely to use Facebook and Instagram because those were the emergent social networks when they were in school.

Broadened to the more traditional demographic of 18- to 24-year-olds, Snapchat’s strength among 18- to 20-year-olds helps the app keep pace with Facebook and fend off Instagram. Snapchat beats Instagram among this age group in four of the seven countries and ties Instagram in Australia.

As Snapchat’s audience gets older, that edge could lead to Snapchat eventually overtaking Facebook among this audience as it has done among 13- to 17-year-olds and 18- to 20-year-olds. Of course, that depends on those younger users remaining on Snapchat as they age and associate with more Facebook- and Instagram-dominant users.

25- to 34-year-olds

Apparently, Facebook is like email: The older you get, the more likely you are to use it. People in their late twenties and early thirties — the heart of the millennial demographic — are more likely to be found on Facebook than Instagram or Snapchat in all seven countries.

Instagram also appears to appeal to more millennials than Snapchat. That may have to do with the Instagram experience more closely mimicking Facebook’s, where people can broadcast posts to groups of friends, as opposed to Snapchat, which originally served ephemeral private messages. That network effect appears to have kept this demographic on Instagram and helped its Stories feature quickly grow to rival Snapchat’s reach. Snapchat only slightly edges out Instagram’s Stories in the US, the UK and Australia, and Instagram’s Snapchat clone has overtaken the original in Germany and Brazil and matched Snapchat in Canada.

35-year-olds and older

Evan Spiegel, CEO of Snapchat’s parent company, Snap, said during the company’s Q1 2017 earnings call in May that “we do tend to market our products directly to younger people because, frankly, they are more interested in learning how to use new technology products.” It shows. Both Snapchat and Instagram are primarily mobile experiences and appear to have had an easier time making inroads with people who largely grew up on their phones. Meanwhile, many adults first learned to use Facebook on their computers and were able to apply that knowledge to speed up their grasp of its mobile version while still also accessing its desktop site. As a result, Facebook remains the domain of the 35-and-older demographic.

That Snapchat doesn’t allow advertisers to break down its 35-plus audience by narrower age ranges also suggests its struggle to attract this demographic and, thereby, to appeal to advertisers looking to reach older audiences, from Generation Xers to Baby Boomers to the Greatest Generation. Instagram also lacks Facebook’s scale among older users, though its integration with Facebook’s ad-buying tools enables advertisers to drill down to more specific age groups among this audience.

How the platforms’ audiences are measured
It’s important to consider these charts in the appropriate context, especially following last week’s Facebook-Census data debacle. Several caveats to be cognizant of include:

Estimates based on recent usage: These numbers are estimates. They are not guarantees of how many people an ad will reach. They are extrapolations of how many people an ad could reach if it were shown to everyone in a defined audience based on how many people could be grouped in that audience over a recent period of time. Snapchat bases its estimate on usage over the past 28 days, while Facebook’s is based on a 30-day average, according to spokespeople for each company.

Reliant on user-reported information: Facebook and Snapchat don’t actually know how old each individual user is. Both companies rely on people to provide their ages accurately, and people may not comply. If they’re under 13 years old and thereby legally barred from joining Facebook or Snapchat, they may say they’re 13 or 30 years old in order to get access.

Audiences include travelers: These audience estimates include everyone in a location, including regular residents and temporary visitors. Both Facebook and Snapchat use location tracking to measure when someone from, say, Canada happens to be in Los Angeles, so that any ads aimed at people in Los Angeles, California, or more broadly, the US, can be shown to that person, too, since they fit that criterion. And if people disable location tracking in Facebook’s, Instagram’s and Snapchat’s apps, then the companies have to rely on other signals to peg where someone might be, like what cell tower or WiFi signal their phones connect to.

Locations logged differently: While both Facebook and Snapchat aggregate their audiences over roughly the past month, they log those people’s locations differently. Each time Facebook logs a person’s location, it updates its records so that the person is only included in the count for that most recent location. When Snapchat logs a person’s location, it’s added to a list of other locations logged for that person over the most recent 28 days, and the person is included in the count for each location recorded in the period. As a result, a person from Mexico may have traveled to the US on September 1, used Facebook and Snapchat while sightseeing, returned to Mexico on September 4 and never left. If an advertiser used Facebook’s and Snapchat’s self-serve tools on September 13 to target people in the US, that person would not be included in Facebook’s potential reach estimate but would still be included in Snapchat’s estimate (though Snapchat would not actually deliver an ad to that person). And if the advertiser were using the tools on September 13 to target people in Mexico, the person would be included in both companies’ estimates and, since that person remained in Mexico, they would be among the people eligible to see the advertiser’s ad.

Numbers may fluctuate: Both Facebook’s and Snapchat’s figures are updated daily, so the counts included in these charts may have changed by the time you view them for yourself in Facebook’s and Snapchat’s tools. For example, I pulled the numbers on September 5 and then again on September 7, and several had increased or decreased by as many as 1 million people for Facebook, Instagram’s main feed, Instagram’s Stories feed and Snapchat in that two-day span, likely spurred by August being a popular travel month.