Guide

Interest Based Marketing on Instagram: How to Grow Organically

GustafGustafFounder, Postjam

Interest based marketing on Instagram means making content for one interest, so that Instagram's delivery system can find the people who hold it and keep sending them your posts. It is the companion to niche marketing on TikTok, and it exists because Instagram decides who sees a Reel differently: TikTok reads a community you can browse by hashtag, and Instagram reads an interest it has built up, watch by watch, about every person on the platform.

If your reach has fallen and copying what works for bigger accounts no longer moves it, this is why, and it is within your control. This guide explains how Instagram decides who sees a post, why trend copying stopped working, what number to watch in its place, and the five steps that grow an app on Instagram without ads.

Contents

How Instagram decides who sees a Reel

Instagram shows a person a Reel, and watches what they do with it. Watch it to the end and the system notes that something in it landed, then tries a related one later. Watch that to the end too, and it gets more confident, and tests neighbouring interests to find the edges: someone who watches primitive camping is probably interested in backpacking and survival, and over weeks the category narrows to something as specific as winter wilderness survival.

Every feed is now built this way, from demonstrated interest rather than from what is trending. Meta holds the largest store of behaviour data there is, and it chose to spend it on delivery, so the system knows a person's interests at a resolution no creator can match. Your Reel is sent to the people whose interest it fits, and it is the Reel itself, its words, its sounds and what is on screen, that tells the system which interest that is. US Targeting on Instagram: How to Reach American Viewers covers the country side of the same fact.

Why copying trends stopped working

Between 2020 and 2023 attention was cheap. People had time, short-form video was new, and every feed pushed whatever was being engaged with, with no regard for what a particular person cared about. Copying a trend worked because the platform rewarded the copy. Accounts built in that period got huge on content that was the same as everyone else's.

Then attention contracted. People went back to work, feeds became personal, and viewers who had less time to spend became choosier about what they spent it on. The accounts that grew in the easy years now get less reach per follower than smaller accounts built for one interest, and a new account running the old playbook, copying what the big accounts did, gets nothing at all. The algorithm is the usual suspect. The usual cause is that the content is generic, and generic content fits no one's interest.

The same mistake hides in how people describe their audience. An app's category is a shelf, and "productivity", "fitness" and "finance" are not interests anyone holds. Nobody watches productivity. People watch study-with-me sessions, desk setups, and a particular kind of person talking about a particular kind of morning.

Saturation beats reach

Raw reach is the wrong number to chase now. The number that matters is saturation: what share of one interest's audience your account holds the attention of. A million views spread over people with nothing in common builds nothing. Ten thousand views inside one interest, post after post, builds an audience that recognises you and a delivery system that knows exactly who to send your next Reel to.

This is good news for a small account, because you choose the pond. Pick an interest with a million people in it and become the account they all see, and you are a big fish with no competition, on a platform that will keep introducing you to the rest of the pond. An app does not need a billion views. It needs the people whose problem it solves to keep seeing it.

Step 1: Name the audience by interest

Ask two questions of any app, in this order. Who do I want watching, and what do they want to watch?

The first answer has to be specific enough to picture a person. "People who use their phone too much" is a huge slice of humanity and cannot be targeted. Make an educated guess about the kind of person who would find your app irresistible, and follow that guess into the interests they hold. A screen time app could go after nursing students, who study in long blocks, live in the library for weeks before exams, and already watch study-with-me content and desk setups. Or it could go after parents of a first phone, who watch a different feed entirely. Each is an interest with a shape. The category has none.

Look at who the interest is made of. Size, spare money, whether they pay for apps, whether anyone is already making content for them. An interest with a million people and no one speaking to them is a better pond than one with ten million and a hundred accounts already in it.

Step 2: Watch what they watch

Instagram shows you what an interest wants to see, provided you ask it the right way. Make a fresh account, follow nothing, and watch only the interest: search for it, watch the Reels to the end, save the good ones, ignore everything else. Within days the feed narrows to what that audience is being shown, which is the research you need.

Note the same four things as on TikTok: the hooks, the text on screen after the hook, the sounds, and the formats that keep coming back. Read the comments too, since the comments say what the audience wanted and did not get. Twenty hooks, five sounds and two or three formats are enough to start.

Step 3: Make it, with the app inside

Now find the overlap between what the interest wants to watch and what you can make on repeat. Both matter. Content the audience loves that you can only make once a month is a hobby, and content you can make every day that nobody in the interest wants is noise.

Take the nursing students. They watch long phone-free study sessions and desk setups. So make phone-free study sessions, and let the screen time app be the thing that makes the session possible: the phone locked on the desk, the timer running, the block ending. The app is the demo and the interest is the format. Nobody in that feed is being sold a productivity app, and everyone in it can see one working.

The same move works for any app. Find the activity the interest already films, and put the app inside it doing its job. Value first, and the app as the reason the value exists. A Reel that provides something the audience wants is trusted, and a trusted account is one whose link gets tapped.

Step 4: Stay in the lane

Every post trains the delivery system on who to send the next one to. An account that posts for one interest, and only that interest, gets sharper delivery with every Reel, because each one confirms the last. An account that posts a study session on Monday and a trending dance on Tuesday tells the system nothing it can act on, and both posts are sent to nobody in particular.

So one interest per account. When the first interest works and you want a second, make a second account and let it build its own audience. The creators with the most dedicated audiences on the platform know precisely what their lane is and never leave it, and the reward is an audience of millions across every platform they post to, from content about one thing.

In Postjam this is one automation per account, scheduled, so the lane holds without you thinking about it. Every post the automation makes speaks to the same interest, and the account never drifts.

Step 5: Experiment, then double down

Research gives you direction. It does not tell you which of the twenty hooks the interest will stop for, or which of the three formats it will watch to the end. Only posting does. So post every day, watch which Reels get watched through and saved, and then make more of those. Doubling down on what the audience already chose is the whole strategy, and it beats a clever guess every time.

Give a format thirty posts before you judge it, and change one variable when you do. Postjam's analytics show each automation's numbers account by account, so a post that lands on one account and dies on another says something about the interest rather than the format.

How this differs from TikTok

On TikTok the unit is a community, and you can read it by searching a hashtag and studying the top posts. On Instagram the unit is an interest the system has built up about each viewer, and you read it by watching the feed of a fresh account. The method is the same shape: pick one, learn its language, make what it already watches, post every day. The research surface is different, and the discipline is stricter, because Instagram's delivery is built on the history of everything an account has posted.

A format that works on TikTok is worth posting to Instagram. Just expect it to land on a different group of people there, and read the account's analytics separately.

FAQ

Do hashtags matter on Instagram? Less than the content. Instagram reads what is in the Reel, and hashtags are one small signal among the words, the sound and what is on screen. Use the ones the interest uses and spend the effort on the Reel.

How many followers do I need? Fewer than you think. Delivery is per Reel, from the interest it fits, so a new account inside one interest can out-reach an old account with a hundred times the followers. Followers are a result of saturation, and a poor measure of it.

Should I post trends at all? Only a trend the interest itself is running. A trend from outside the interest tells the delivery system you post about something else, and the account pays for it on the next Reel.

Can I run several interests on one account? No. Each interest gets an account, and the second account starts once the first has a format that lands.

How long before it works? Thirty posts inside one interest is the first honest read. Before that the delivery system is still working out who you are.

Recap

Instagram sends a Reel to the people whose interest it fits, and builds that fit from everything you have posted. Trend copying stopped working when attention got scarce and feeds got personal. Chase saturation of one interest rather than raw reach. Name the audience specifically, watch what they watch on a fresh account, make that content with your app inside it, keep the account in one lane, and double down on what the audience chose.

Next, read Niche Marketing on TikTok: How to Grow an App Organically for the TikTok side of the same method, US Targeting on Instagram: How to Reach American Viewers for the country the Reel lands in, and How to Fully Automate UGC Videos in Postjam to post the format every day.

Keep reading

ClaudeCursor

Your agent can build. Now it can post.

Organic social has been solved.

{
  "mcpServers": {
    "postjam": { "url": "https://mcp.postjam.app" }
  }
}
Or start on the web