What is a side project?
A side project is something you build in your spare time, outside your main job, usually with no pressure to make money. Many become businesses: Gmail, Slack and Gumroad all started as side projects, and most indie makers ship several before one earns enough to quit.
What counts as a side project
A side project is anything you build outside your main job or studies: an app, a website, a game, a newsletter, a browser extension, a dataset. It differs from a side hustle in intent. A side hustle is about extra income from day one; a side project can be for learning, curiosity or fun, and only sometimes turns into money.
That freedom is the point. With a salary covering the bills, a side project can be small, odd or slow, and still be worth doing. It is also the most common way independent businesses start: 97 profiles in our directory describe a product that began as a side project, in spare time or alongside a job.
Famous side projects that became businesses
Some of the best-known products on the internet started this way. Gmail began as Paul Buchheit's project inside Google and launched in 2004, and Slack grew out of the internal chat tool of Tiny Speck, a company building an online game called Glitch that failed (Wikipedia). Gumroad started as a weekend project by Sahil Lavingia while he worked at Pinterest.
The indie versions are more useful to study, because they were built by one or two people with no company behind them. These all started next to a job, studies or freelance work:
| Started | Side project | Maker | Doing at the time | What it became |
|---|---|---|---|---|
| 2007 | CSS-Tricks | Chris Coyier | learning CSS, documenting it as he went | One of the best-known front-end blogs; sold to DigitalOcean in 2022 (source) |
| 2011 | Plague Inc. | James Vaughan | strategy consultant | A strategy game with more than 160 million downloads (source) · revenue |
| 2012 | Publer | Ervin Kalemi | recent graduate (built it over a Thanksgiving weekend) | A bootstrapped social media tool on the road to about $3M ARR (source) · revenue |
| 2012 | Storemapper | Tyler Tringas | freelancer | A one-person store-locator SaaS sold at roughly $40K MRR in 2017 (source) · revenue |
| 2013 | Stratechery | Ben Thompson | Microsoft employee | The newsletter that pioneered the paid one-person subscription model (source) |
| 2014 | Insomnia | Gregory Schier | software engineer | An API client sold to Kong in 2019 at about $20K MRR (source) · revenue |
| 2014 | Geocodio | Michele Hansen | employed (went full time on Geocodio in 2017) | A geocoding API run by a husband-and-wife team (source) |
| 2014 | Remotive | Rodolphe Dutel | Buffer employee | A bootstrapped remote job board and newsletter (source) |
| 2015 | Healthchecks.io | Pēteris Caune | Python developer | A one-person cron monitoring service at $26K MRR (source) · revenue |
| 2016 | Keygen | Zeke Gabrielse | developer (nearly a year before the first paying customer) | A software licensing API he has run for a decade (source) |
| 2016 | Listen Notes | Wenbin Fang | engineer at Nextdoor | A podcast search engine and API run as a tiny company (source) |
| 2017 | Key Values | Lynne Tye | freelance developer | A solo job board making about $30K a month by 2019 (offline since 2025) (source) · revenue |
| 2021 | Wordle | Josh Wardle | employed; made it as a gift for his partner | A daily word game sold to The New York Times in 2022 (source) · revenue |
The pattern: almost none of these were planned as companies. Josh Wardle made Wordle for his partner; Chris Coyier started CSS-Tricks to document what he was learning; Gregory Schier started Insomnia as a side project for testing HTTP APIs. They became businesses because other people needed the same thing.
Side-project makers by the numbers
- 97
- Profiles with a side-project origin
- 26%
- Of them have sold a product
- 24
- Countries
- 26
- Built or build alongside a job
- SaaS Founders24 · 25%
- Indie Game Makers14 · 14%
- AI Builders9 · 9%
- Creators & Writers7 · 7%
- Open Source Makers6 · 6%
- Developer Tools5 · 5%
- Directory Makers4 · 4%
- Educators & Course Creators4 · 4%
- United States29 · 30%
- India8 · 8%
- United Kingdom7 · 7%
- France6 · 6%
- Canada3 · 3%
- Germany3 · 3%
- Poland3 · 3%
- Hungary2 · 2%
Counted from profile bios and dated milestones that mention a side project, spare time, or building alongside a job. Many more makers started the same way without saying so, so this is a floor, not a total.
Makers who built alongside a day job
Keeping the job is not a lack of commitment; it is how most of these products survived their first years. These makers built, or still build, their products next to employment:
- Simon Høiberg: Ex-LEGO engineer building a bootstrapped SaaS portfolio: FeedHive, Aidbase, LinkDrip
- Ruben Gamez: Bootstrapped founder of SignWell e-signatures and Bidsketch proposals
- Piotr Obidowski: Polish engineer-turned-indie hacker behind Visualizee.ai AI renders
- Tristan Roth: ISO 27001 consultant building ISMS Copilot, heyGRC and Aevral without investors
- Billy Basso: Chicago solo developer who spent seven years building the hit Metroidvania Animal Well
- Tushar Kapil: Mumbai developer building Reachlee, Instagram DM automation at about $1.9K MRR
- Sergey Nazarov: Solo founder of Screen Charm, a Mac screen recorder with automatic zoom effects
- Max Rozen: Australian engineer in France running OnlineOrNot, a self-funded uptime monitoring SaaS
- Richard Kovacs: Budapest full-stack developer and security trainer shipping AI side projects at night
- Raj Vikramaditya (Striver): Creator of takeUforward and the Striver DSA sheets; ex-Google engineer turned founder
- Bart Proost: LA engineer at Anyscale who builds brew.fm for Spotify and the tennis app Doyouplay
- Devin Davies: Creator of Crouton, the recipe app that won a 2024 Apple Design Award
- Xiao Lan: Chinese programmer and indie maker of Nabreel (小剪箱), an online video toolbox
- Mathias Michel: German developer building RewriteBar, an AI writing assistant for macOS, on the side
- Andrew Chemerynskiy: Wrocław frontend engineer and serial maker who sold the InGastro job board for $13.5K
- Hien Nguyen Trong: Vietnamese senior engineer building Zero Revenue Club, EnvDesk and ShipTale
- Harry Ashton: UK frontend engineer building CodePrepped and the Hashton AI automation agency
- Michael Burkhardt: 9to5Mac writer and indie iOS developer behind Ruby and the upcoming Amethyst
- Dilyan Dimitrov: Copenhagen software engineer building Race Calendar BG and Amounthly alongside a 9-5
- Hoa Nguyen Xuan: Hanoi-based product manager and nights-and-weekends maker of SmartGantt and FeedbackGlow
- Yusuf Gürdoğan: Developer behind the Benture remote job board and the Browsynth browser synth
- Vishnu Aniyan: Kerala-based digital manager building Formwrapper, forms backed by Google Sheets
- Rafał Darłak: Cloud architect building BrandPicked, an AI recommendation tracker for SaaS
- Deep: AI researcher and DevOps engineer building llmwise, every top AI model on one plan
- FRUNKLA: German car engineer building finance and game apps, including ProofTicker
- Kartik Labhshetwar: Developer behind Better Shot, Screenshot Studio and UsefulShelf
Several turned the side project into the main job. Ruben Gamez kept his job while building Bidsketch on nights and weekends and left once it replaced his salary. Billy Basso worked on Animal Well alongside a day job from 2017 and quit in 2022 to finish it. LocalThunk started Balatro on a vacation from his IT job.
How to start and grow a side project
- Scratch your own itch. Tools you need yourself are easiest to judge. Keygen, Insomnia and Healthchecks.io all started as developer tools their makers wanted.
- Make it tiny. Aim for something you can ship in two to four weekends. A landing page plus one working feature is enough to learn from.
- Fix a weekly rhythm. A few protected hours every week beat a lost month of good intentions. Share progress publicly to stay accountable.
- Launch, even if it feels early. Post it where its users are; see where to launch and how to launch.
- Charge sooner than feels comfortable. Pēteris Caune launched Healthchecks.io as a side project in 2015, had about $700 a month in 2018 and reports $26K MRR in 2026. Small early revenue is a signal worth following.
- Set a quit rule in advance. For example: revenue covers essential costs for three months in a row, plus six months of savings. Read when to quit your job.
- Check your contract. Look for intellectual-property and non-compete clauses, don't use company time or hardware, and stay out of your employer's market.
Side project ideas, from projects that worked
- A tool for your own workflow: an API client, a monitoring service, a license-key server. See developer tools makers.
- A blog or newsletter about what you are learning: CSS-Tricks and Stratechery both started this way. See newsletters by makers.
- A niche job board or directory: Remotive began as a remote-jobs newsletter; read the directory business playbook.
- A small game: Wordle, Plague Inc. and Balatro were all spare-time projects. See games made by one person.
- A data API: Geocodio turned address data into a paid API.
- An AI tool for one task: the fastest-growing category in our micro SaaS data.
Start here: from side project to business
- 01How to become an indie maker →The full path from first project to income.
- 02Glossary →MRR, churn and the rest, once money starts coming in.
- 03How to launch your product →Getting the first visitors and users.
- 04First 100 customers →Turning users into paying customers.
- 05Stripe fee calculator →What you keep from each sale.
- 06When to quit your job →Timelines and thresholds from makers who did.
- 07Maker journeys →Dated timelines from first product to full time.
- 08Indie exits →Side projects that ended in a sale.
Former makers whose side projects became businesses
2 makers who no longer build their own products — most now work at a company. Kept for the record.
Sahil Lavingia
@shl United States394K followers
Founder of Gumroad and author of The Minimalist Entrepreneur
Gumroad, Flexile, Helper$17.8M/yr
Pat Walls
@thepatwalls United States143K followers
Founder of Starter Story, the founder case-study brand acquired by HubSpot in 2026
Starter Story, Starter Story Build$1M/yr
Frequently asked questions
What is a side project?
A side project is a personal project you work on outside your main job or studies, such as an app, website, game, newsletter or tool. It can be for learning, fun or extra income.
What famous companies started as side projects?
Gmail began as Paul Buchheit's project inside Google, Slack grew from the internal chat tool of a failed game, and Gumroad, Wordle, CSS-Tricks and Plague Inc. all started as their makers' spare-time projects.
How do I turn a side project into a business?
Charge for it early, even a small amount, to learn whether people will pay. Track revenue against your salary, cut your costs, and set a clear quit threshold such as a few months of runway plus revenue covering your essential expenses.
How much time should I spend on a side project?
Consistency beats volume. Most makers who succeed alongside a job work a few focused hours on weekday evenings or weekends and ship small updates every week rather than waiting for big blocks of time.
Is it legal to build a side project while employed?
Usually, but check your employment contract for intellectual property and non-compete clauses, avoid using company time or equipment, and stay out of your employer's market. Rules vary by country and state.
When should I quit my job for my side project?
Most makers wait until the project's revenue covers their essential costs or they have 6–12 months of savings. Read our guide on when to quit your job for real timelines from makers who did it.