These two words get used interchangeably in startup circles. They are not the same thing, and treating them as if they are leads to some expensive confusion.
What a campaign is
A campaign is a planned, usually time-limited marketing effort with a defined goal, a defined audience, and a defined set of channels. A product launch campaign. A seasonal promotion. A paid social push to drive sign-ups before a funding announcement.
Campaigns are appropriate when you already know what works. You have a channel that converts, a message that resonates, an audience that responds, and you are putting more resource behind something you understand.
What an experiment is
An experiment is a structured test of a specific hypothesis about why people do or do not do something you want them to do. The hypothesis comes first. Something like: we believe users who receive an onboarding email within the first hour of signing up will activate at a higher rate than those who receive it the next day.
You set up the test, define what would constitute a meaningful result, run it for long enough to get reliable data, and then read the result honestly, whether it supports the hypothesis or not.
The critical word there is honestly. An experiment that is set up to confirm what you already believe is not an experiment. It is a campaign with extra steps.
Why this distinction matters in practice
Campaigns require scale to work well. You need enough budget, enough audience, enough time for the results to be meaningful. Experiments can be tiny. Some of the most important growth discoveries companies have made started with a change that cost almost nothing to test.
The Airbnb example from the first post in this series illustrates this well: the team tested professional photography with a $5,000 camera. The test was small enough to run quickly and cheaply. The result was large enough to change the entire company's strategy.
A campaign mindset would have led to more ad spend. An experimental mindset led to looking at the actual problem.
How experiments compound over time
Most experiments fail to produce a meaningful result. That is expected and fine. A team running structured experiments learns from the failures, adjusts the hypotheses, and tries again. Over time, the experiments that do work get scaled, and by that point you are not guessing. You have evidence.
The growth marketing paradigm provides a framework and tools to quickly identify and stop ineffective strategies, sharpening your focus on actions that lead to success. The key to a successful failure lies in thoroughly analysing what went wrong.
A team that runs ten experiments a quarter and finds one significant lever has done something a team running three campaigns cannot: they have genuinely expanded their understanding of their customers.
When to use which
If you have high confidence in a channel or message, run a campaign and put resource behind it. If you are uncertain, if you are trying to find out whether something works, run an experiment with a minimal budget, a clear hypothesis, and a commitment to reading the result fairly.
Most early-stage companies should be running far more experiments and far fewer campaigns than they do.
Campaigns scale what you know. Experiments find what you do not know yet. Early-stage startups usually need more of the second and less of the first.