Substack Advertising: What Brands Are Getting Wrong

Substack advertising is the practice of placing paid promotions inside Substack newsletters, either through direct deals with individual writers or through Substack’s own ad network. It gives brands access to highly engaged, self-selected audiences in a format that feels closer to editorial than display. Done well, it works. Done badly, it wastes money and annoys readers who specifically came to escape the noise.

The channel is growing fast, and the pitch is compelling: niche audiences, high open rates, low competition relative to social. But most brands entering this space are applying the wrong mental model, treating it like programmatic display when it behaves much more like sponsoring a trusted voice.

Why Substack Is a Different Kind of Ad Inventory

Most digital advertising inventory is built on attention that was captured for something else. Someone searches for a recipe, sees a banner for a software tool. Someone watches a video, gets a pre-roll for a car brand. The ad is adjacent to the content, not part of it.

Substack is different. Readers subscribe to specific writers. They open emails because they trust the person sending them, not because an algorithm surfaced the content. When a writer includes a sponsorship note, readers understand the writer chose to work with that brand. That implicit endorsement carries weight that a display impression simply cannot replicate.

I spent years on the agency side managing display budgets that ran into the tens of millions. The CPM economics looked attractive on paper, but the actual business impact was always harder to isolate. With Substack, the economics look less efficient at first glance, but the quality of the attention is categorically different. You are not buying eyeballs. You are borrowing credibility.

That distinction changes how you should plan, brief, and measure the channel entirely.

Who Should Be Considering Substack Ads Right Now

Not every brand belongs here. Substack advertising makes most sense for brands that have something to say to a specific kind of person, and whose product or service holds up under the scrutiny of a reader who is genuinely paying attention.

It tends to work well for B2B software and services targeting specific professional audiences. A newsletter about financial operations reaching CFOs and controllers is more precise than almost any LinkedIn segment you can build. It also works for consumer brands with a clear point of view, particularly in categories like books, food, health, and personal finance, where Substack has strong readership.

It works less well for brands that need mass reach fast, or for categories where the product is generic enough that the newsletter’s editorial character adds nothing. If you are selling commodity office supplies, the trust transfer from a respected writer does not help you much. You are better off in search.

The brands getting the most from Substack advertising tend to share one trait: they have a genuine perspective on the world the newsletter covers. They are not just buying space. They have something relevant to say to that specific audience.

If you are thinking about how Substack fits into a broader go-to-market approach, the Go-To-Market and Growth Strategy hub covers the channel and audience planning decisions that sit upstream of any individual media choice.

How Substack Ad Placements Actually Work

There are two main routes into Substack advertising. The first is Substack’s own network, which allows brands to run ads across multiple publications through a single buy. The second is direct negotiation with individual writers.

The network route is more scalable and easier to manage operationally. You set targeting parameters, agree a budget, and Substack distributes your ad across relevant publications. The tradeoff is control. You cannot always choose which specific newsletters carry your message, and the placement quality varies considerably across the network.

Direct deals give you more control over tone, placement, and the relationship with the writer. Many of the best Substack writers are selective about who they work with, which is actually a signal of quality. A writer who turns down irrelevant sponsors is protecting the trust of their audience, and that audience trust is exactly what you are trying to access.

In practice, the most effective Substack campaigns I have seen combine both: direct deals with two or three high-fit writers where brand alignment is tight, and network buys for broader reach testing. You learn faster from the direct deals, and the network scales what works.

Placement formats vary by writer, but the most common are: a dedicated sponsorship section at the top or bottom of the newsletter, mid-content integration where the writer weaves the brand into their editorial, and standalone sponsored issues where the entire edition is branded. The mid-content integrations tend to perform best when the writer genuinely uses and believes in the product. They perform worst when the copy reads like it was pasted in from a media pack.

The Briefing Problem Most Brands Get Wrong

Early in my agency career, I worked on a campaign where the client handed us a brief so locked down that there was no room for the creative team to do anything interesting. Every line had been pre-approved by legal. Every claim had a footnote. The work that came out was technically correct and completely forgettable.

Substack briefing has the same failure mode, just in a different direction. Brands send over a standard influencer brief, complete with mandatory claims, approved hashtags, and a list of phrases the writer must include. The writer produces something that sounds nothing like them. Their readers notice immediately. The sponsorship falls flat.

The brief for a Substack placement should explain what you are, who you are for, and why you think this particular audience might find you useful. It should give the writer the information they need to write honestly about you in their own voice. It should not script the copy. The writer knows their audience better than you do. Let them do their job.

This requires a degree of trust that feels uncomfortable if you are used to controlling every brand touchpoint. But the discomfort is the point. The reason Substack advertising works is because it does not look like advertising. The moment it does, you have lost the thing you were paying for.

For brands building creator relationships at scale, Later’s work on creator go-to-market strategy is worth reading. The principles around creative freedom and brand fit apply directly to how you approach Substack writers.

Measuring Substack Advertising Without Lying to Yourself

One of the things I took away from judging the Effie Awards was how rarely brands measure the right things. The entries that struggled were not the ones with modest results. They were the ones measuring activity instead of outcomes, or measuring short-term outcomes while ignoring longer-term brand effects.

Substack advertising has a measurement problem that is easy to misread. Open rates for newsletters are high relative to most digital channels, but they do not tell you whether anyone acted on the sponsorship. Click-through rates are trackable with UTM parameters, but click volume is typically low relative to impression counts. Last-click attribution will almost always undervalue the channel because many readers see a Substack mention, sit on it for a week, and then convert through a different channel entirely.

Earlier in my career, I overvalued lower-funnel performance metrics. It took me longer than I would like to admit to recognise that a lot of what performance channels were getting credit for would have happened anyway. The person who was already in-market, already searching, already comparing options, would have found us through some route. What we were not doing was reaching the person who did not know they needed us yet.

Substack is primarily a reach and awareness channel. Measure it accordingly. Track brand search volume trends over the period you are running placements. Run brand lift surveys if your budget supports it. Use promo codes or dedicated landing pages to capture what you can. And accept that some of the value will not be directly attributable, because that is the honest reality of how upper-funnel channels work.

Tools like Crazy Egg’s growth tracking resources and SEMrush’s suite of growth tools can help you build a cleaner picture of what is moving across channels, even when direct attribution is incomplete.

Finding the Right Newsletters: What to Look For Beyond Subscriber Count

The most common mistake brands make when sourcing Substack placements is optimising for audience size. A newsletter with 200,000 subscribers looks more attractive than one with 8,000. But subscriber count tells you almost nothing about the quality of the audience or the engagement the writer generates.

What you actually want to assess is open rate, which Substack writers can share on request. A newsletter with 8,000 subscribers and a 55% open rate is reaching more active readers than one with 50,000 subscribers and a 12% open rate. Engagement in the comments section is another signal. Newsletters where readers respond, debate, and reference the writer’s previous work have a community dynamic that amplifies the impact of any sponsorship.

You also want to assess editorial fit, which is harder to quantify but more important than any metric. Read several issues before you approach the writer. Ask yourself whether your brand could plausibly be mentioned in this newsletter without feeling out of place. If the answer is no, move on. A technically efficient placement in the wrong editorial context is still a wasted placement.

Longevity matters too. A newsletter that has been running consistently for three or more years has demonstrated that the writer is committed and that the audience has staying power. New newsletters can work, but they carry more risk.

Substack Advertising as Part of a Broader Growth Strategy

When I was growing an agency from around 20 people to over 100, one of the hardest things to manage was the temptation to only invest in channels that produced immediately measurable results. Everything that could not be tied to a conversion in the same week felt like a risk. That mindset is understandable under commercial pressure, but it is also how you end up with a business that only captures existing demand and never creates new demand.

Substack advertising is not a performance channel. It is a reach channel with unusually high credibility. The right way to position it in a growth plan is alongside other upper-funnel investments, not instead of them. It works well in combination with organic content, podcast sponsorships, and earned media. It works less well as a standalone channel with no supporting brand presence.

BCG’s research on brand and go-to-market strategy alignment makes a useful point about the relationship between brand investment and commercial performance. The brands that scale consistently are the ones that treat brand and performance as complementary, not competing. Substack sits firmly in the brand and awareness column, and that is where it should be budgeted and evaluated.

Forrester’s thinking on intelligent growth models reinforces this. Sustainable growth requires reaching audiences who do not yet know you exist, not just converting audiences who are already looking for you. Substack is one of the more efficient ways to reach genuinely new audiences in specific niches, particularly for brands where the product requires some explanation or context before a purchase decision makes sense.

There is more on building channel strategies that balance short-term performance with longer-term audience development across the Go-To-Market and Growth Strategy hub, including how to think about channel sequencing and budget allocation across funnel stages.

What a Good Substack Campaign Looks Like in Practice

To make this concrete: a B2B software brand targeting operations leaders in mid-market companies identifies three Substack newsletters covering supply chain, business operations, and finance. Each has between 5,000 and 15,000 subscribers with open rates above 40%. The brand approaches each writer directly, shares a clear brief that explains the product and the audience it serves, and gives the writer latitude to write about it in their own words.

Each placement runs with a unique promo code and a dedicated landing page. The brand also tracks branded search volume weekly during the campaign period. After six weeks across three newsletters, click volume is modest but conversion rate from those clicks is higher than any other paid channel. Brand search volume has increased. Two of the three writers have received reader replies mentioning the sponsor positively.

That is what a well-executed Substack campaign looks like. It is not dramatic. The numbers are not the kind you put on a slide to impress a board. But the quality of the audience reached, and the trust transferred in the process, is genuinely hard to replicate through any other channel at a comparable cost.

Compare that to the brand that runs the same budget through Substack’s network, uses boilerplate ad copy, tracks only clicks, and declares the channel a failure after four weeks because the CPL is higher than Google search. Both brands ran Substack advertising. Only one ran it correctly.

About the Author

Keith Lacy is a marketing strategist and former agency CEO with 20+ years of experience across agency leadership, performance marketing, and commercial strategy. He writes The Marketing Juice to cut through the noise and share what works.

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