If you're like me, marketing is not your favorite part of building a product.

Most indiehackers love coding, designing, or solving problems but when it comes to promoting our work, we either procrastinate or default to tweeting into the void.

But what if you could turn your love for building into a marketing strategy?

That's where Engineering as Marketing (or Side Project Marketing) comes in. Let's see how free tools and mini-apps can outshine ads, blogs, and cold outreach --- and how Unsplash actually started as a side project built in just 3 hours which not only saved Crew from running out of cash but later grew into a standalone product attracting over 11 million unique visitors every month.

Engineering as Marketing: What the hell is that?

Think about the last time you used a free tool that solved a simple but specific problem.

• A cron expression generator.

• A quick SEO analyzer.

• A business name generator.

Chances are, that tool wasn't the company's main product. It was just their clever way of getting you through the door.

That's exactly what Engineering as Marketing is:

Building a useful free tool that attracts your ideal users and points them toward your main product.

Instead of cold emails or ads, you're creating value upfront. The free tool becomes your lead magnet.

Why does this work so well?

Side project marketing isn't new but it works brilliantly for indiehackers and small teams because:

• It plays to your strengths. Instead of forcing yourself to tweet every day, you're coding which you already enjoy.

• Free products spread faster. Journalists, bloggers, and communities are much more likely to share a free tool than a paid one. "Check out this cool free thing" is an easier sell.

• It gives first, asks later. Users get value before you ask them to sign up or buy. That builds trust instantly.

• It builds credibility. Even a tiny tool shows you can ship. For new companies, this can be the first proof point that you're legit.

What formats can it take?

Engineering as marketing doesn't always mean building a full-fledged app. It can be simple, lightweight, and focused. Here are some formats that work:

• Calculators & Simulators (e.g., mortgage calculator, ROI estimator)

• Templates & Frameworks (e.g., Notion trackers, Airtable bases)

• Knowledge bases or free courses

• Technical tools for developers (e.g., API wrappers, playgrounds)

• Quizzes & Assessments (lead scoring disguised as fun tests)

• Content tools (e.g., free blog post title generator)

• Trackers & Planners (habit trackers, launch checklists)

• Interactive builders (logo maker, mockup generator)

• APIs or Data sets (open APIs with basic functionality)

What makes a good side project?

Not every free tool turns into a growth engine. Here are the characteristics of a good one:

• It genuinely provides value. A side project should solve a real problem or save people time in a way that feels meaningful. If users don't walk away thinking "that was useful," they won't return or share it.

• It's quick and cheap to build. The best side projects are built in days or weeks, not months. Remember, it's a marketing experiment, not your next main product, so speed matters more than polish.

• It's cheap to maintain. A clever idea that requires constant bug fixes or server costs will drain your energy. Ideally, your tool should run quietly in the background with minimal upkeep.

• It attracts qualified leads. The most important factor. Your side project should bring in people who are likely to care about your main product. A fun meme generator might go viral, but it won't help if you're selling SaaS for startups.

• It's niche-focused. Broad tools often drown in competition. A narrow, specific use case (like a calculator for book readers or a cron job generator) will stand out and reach the exact people you want.

• It doesn't need monetization. The value of a side project is in visibility and lead generation. If you try to monetize it directly, you risk complicating its role as a free and shareable entry point.

• It uses your unfair advantage. Maybe you have access to unique data, strong technical skills, or an insider's view of a niche. Leaning into that edge makes your tool harder to replicate and more useful.

• It's easy to explain. If your tool can't be described in one clear sentence, people won't spread it. Simplicity makes it easier to share on social media, in newsletters, and by word of mouth.

Examples you've probably seen

Some classics in the wild:

• Crontab Guru: A dead-simple cron expression generator. It's not a company's main product, but it ranks high on Google and has become the go-to for developers.

• Books Calculator: Marc Lou built this simple tool to show that reading just 15 minutes a day adds up to 19 books a year. Once people see that potential, many naturally want a habit tracker leading them to his main product, Habits Garden.

• Founderpal Free Tools: A collection of calculators and helpers for startup founders. These tools attract the exact people Founderpal wants as customers: founders, and funnel them into its paid products.

• Unsplash: This one's legendary. Crew, a freelance marketplace, was struggling. So they launched a free photo site as a side project. It blew up, saved their company, and later grew into its own massive brand. Read full story here.

• HubSpot Website Grader: This free SEO audit tool graded millions of websites. It didn't just bring leads---it educated businesses about SEO, which naturally led them to HubSpot's software.

• Ahrefs Keyword Generator: Instead of hiding all their SEO power behind a paywall, Ahrefs gives away a basic version for free. Marketers searching for keyword help find this tool and eventually graduate to the full product.

• Shopify Business Name Generator: Helps new entrepreneurs brainstorm names. Guess what most of those entrepreneurs also need? A storefront platform conveniently offered by Shopify.

Each of these tools is simple, useful, and aligned with their main product's target audience.

How to build your first side project?

Here's a lightweight playbook you can follow:

1. Start with your product or audience. Think about the exact type of people you want to reach. What problems sit just outside your main product? Solving these adjacent pain points makes your tool feel like a natural bridge to your core offering.

2. Pick a small, good idea. Scope it to something you can build in 3--5 days, not months. A tiny, sharp tool that does one thing well is more likely to spread than a bloated side project you never finish.

3. Build a basic version. Don't over-engineer. Focus on getting the main functionality working even if the design is minimal. The goal is usefulness, not perfection.

4. Ship small. Before blasting it everywhere, share with a few trusted friends or communities. Early feedback helps catch issues and makes the final launch stronger.

5. Launch bigger. Once you've validated it, release it to places like Product Hunt, Hacker News, Reddit, or niche Slack groups. These platforms love free tools and can generate a lot of visibility.

6. Review results. Look at whether the tool is actually driving traffic, signups, or awareness for your main product. Data and feedback will show if it's working or just noise.

7. Decide. If it's driving value, keep improving it. If not, shut it down without guilt. Remember, the purpose was to experiment, not to build another startup.

8. Grow. For winners, iterate with small improvements or spin up complementary tools. A suite of free resources can compound traffic and create a stronger funnel for your product.

Wrapping up

Marketing doesn't always have to mean Twitter threads, cold DMs, or ad spend. For indiehackers, sometimes the best way to market is to build something small, free, and useful.

Side project marketing is more than a growth hack, it's a mindset shift. Instead of interrupting people with ads, you're helping them first.

And who knows? That tiny side project you hacked together in a weekend could be the reason your main product gets discovered.