7 Best Tools to Find a Cofounder for a Side Project (2026)

Where nights-and-weekends builders meet, what each tool costs, and how to test a part-time partner before you commit

By Founder Compass · Updated 26 October 2026

At a glance

Costs and rules: each tool's own page, 26 October 2026.

Why is a side-project cofounder different?

Because the deal is different: limited hours, no salary, and no promise it becomes a company. Most cofounder guides on page one of Google assume full-time intent, and at least one lists a partner who keeps a day job as a red flag. For a side project, that's the starting point.

Part-time founders aren't rare. In YC's 2021 data, 43% of people on its matching platform worked full-time on their startup, 22% worked 20-40 hours a week, and the rest gave it under 20 hours. Hours also topped what people cared about: 79% wanted a cofounder who could commit a set number of hours in the coming weeks (YC, 2021).

So a side-project partner needs three things:

• Your commitment level. Six hours a week paired with twenty usually leaves one person waiting.
• Visible work, or a way to test working together. You won't have months of office time to find out.
• A low-pressure start. A small project first, not a company.

1. Foundinity: matched on commitment and how you work

A side project needs two people who expect the same thing, not one who wants to ship every weekend and one who can manage an evening a month. Foundinity matches on exactly that kind of fit.

What it is: a cofounder matching platform for people looking for a cofounder, technical and non-technical.

How it works:

• Preferences + a deeper assessment. You state your preferences, then an assessment captures how you work: working style, ambition, commitment, vision and values, alongside skills. A multi-trait algorithm "built on established psychological compatibility models" ranks the result, so you see compatible people instead of hundreds of random profiles.
• Compatibility breakdown. Every match shows where you align and where you differ, so a gap in commitment or ambition shows up before you've built anything together.
• A 10-day clock on every match. Side-project conversations drift easily; the clock turns matches into calls instead of chats that sit unanswered. You book intro calls right where you match.
• Private by default. Your profile isn't public, and only compatible members can see it. That helps if you have a day job and would rather not search in public.

Cost (checked Oct 2026): free to get started: 5 likes a week, up to 3 active matches and up to 3 profile saves. Plus is $5 a week or $15 a month (₹300 / ₹1,000 in India): 15 likes a week, unlimited active matches, everyone who liked you, the full compatibility score and breakdown, and up to 5 profile saves.

Best for: anyone who wants a partner at the same commitment level, and who'd rather spend a weekly like on a compatible person than send dozens of cold messages.

Try Foundinity

2. Indie Hackers: watch people build in public

Indie Hackers is a forum where founders share what they're building. There's no matching tool; the value is months of posts that show how someone works.

• Watch-outs: Indie Hackers retired its Groups feature in 2026, including the "Looking to Partner Up" board. Cofounder requests still appear as ordinary posts, so you post and search yourself, and older requests are often stale.
• Cost (checked Oct 2026): free.
• Best for: bootstrappers who want a partner they've already watched ship something.

3. Reddit: r/SideProject and r/cofounder

r/SideProject is where people show what they've built; r/cofounder is where people say they're looking.

• r/SideProject describes itself as "a subreddit for sharing and receiving constructive feedback on side projects" and has about 881,000 members (GummySearch). Use it to find builders working near your idea, give real feedback, then message.
• r/cofounder has about 62,000 members (GummySearch). Its rules ask for "a solid business plan and a project ready to go", one skill and one country in the title, and your location in the post.
• Watch-outs:
  • r/SideProject's top theme is self-promotion and cofounder requests aren't among its themes (GummySearch), so don't post a recruiting ad there.
  • r/cofounder bans job seekers and vendors, and expects more than an idea.
  • Usernames are anonymous, so you check people yourself before a call.
• Cost (checked Oct 2026): free.
• Best for: finding builders by their projects (r/SideProject) and posting a clear pitch with your weekly hours (r/cofounder).

4. Hacker News: find technical builders through Show HN

Hacker News has no cofounder board, but Show HN is a steady stream of people showing what they've built. Its rules say Show HN is "for something you've made that other people can play with". There were 3,737 Show HN posts in September 2026 (HN Search by Algolia).

• How to use it: search Show HN for projects near your idea, try them, and leave a useful comment. If the maker lists contact details or a project site, reach out about their work first and your project second.
• Watch-outs: most makers aren't looking for a partner. If you post your own Show HN, the rules rule out landing pages and "quickly-generated one-offs", so you need something people can try.
• Cost (checked Oct 2026): free.
• Best for: finding a technical cofounder for a side project, by judging their work before you write. More routes in our guide to the best places to find a technical cofounder.

5. Online hackathons: Devpost and MLH

A hackathon is a scoped first project with a deadline built in, which is exactly the test a side-project partnership needs.

• Devpost listed 39 open online hackathons on 26 October 2026 (Devpost), many with submission windows of several weeks that fit around a job. Each hackathon has a Participants page where you can tick that you're looking for teammates and send a "Team-up request".
• MLH runs and lists hackathons; its next six events after 26 October 2026 are all in person. It says about 15% of software engineers worldwide got their start through MLH (its own figure).
• Watch-outs:
  • On Devpost, "You'll only be able to message each user one time," so make the first message count.
  • A prize shows speed, not staying power, and many participants are there for prizes or practice, not a partner.
  • Costs and eligibility vary by event; check each one.
• Best for: testing a possible partner on a real build before either of you commits more.

6. FoundersList: free listings that welcome side projects

FoundersList is a directory of cofounder listings you browse yourself. Its page speaks directly to people "looking to collaborate with someone on a side-project".

• Watch-outs: the listings page shows no dates, so you can't tell which are still active, and it says nothing about checking members. It says it has "300+ cofounder listings" (its own figure).
• Cost (checked Oct 2026): posting a listing and messaging are free, per its page.
• Best for: posting a short side-project listing with your stage, skills needed and weekly hours, and sorting other listings by cofounder type, location and stage.

7. YC's cofounder matching: a large free pool, if you're upfront about hours

Y Combinator's cofounder directory is free, and you don't need to be in YC. You build a profile, browse others and send invites; a match happens when someone accepts.

• Watch-outs:
  • It's only for finding a cofounder: the FAQ says using it for anything else can get you removed, so don't use it for a hobby collaborator with no company in mind.
  • Your profile must be approved first, which "may take up to a week", and invites are capped at 15 a week.
  • A 2023 Ask HN thread asked exactly whether it's fine for a side project; the replies said yes, if you're upfront about your intentions (Hacker News).
• Cost (checked Oct 2026): free; YC calls it "a completely free product". It's open whether you're "already working full-time on a startup or just interested in doing one in the future".
• Best for: side projects you'd like to grow into a company. YC says over 100K matches have been made (its own undated figure); you sort that pool yourself.

How do you test a side-project partner?

Agree on weekly hours in writing, then build one small, scoped thing together in two to four weeks. YC's startup library suggests a fun side project with a candidate, "something that builds confidence that you can work well together" (YC Startup Library).

1. State your hours up front. For example: "six hours a week, Tuesday evenings and Saturday mornings." YC's FAQ lists the same question to discuss early: how many hours a week can each of you give?
2. Scope a first project you can finish. One feature, a landing page plus ten user interviews, or a hackathon entry. YC's FAQ says a trial can be "a small piece of a larger startup idea, or even something totally unrelated", and recommends "2-4 weeks of close work".
3. Set the rhythm. One weekly call and one shared async channel. Side-project partners often work at different hours; our guide to remote cofounders covers working apart.
4. Split the work clearly. Who builds, who talks to users, who decides when you disagree.
5. Review honestly at the end. Did each of you put in the hours you said? Then choose: keep going, go bigger, or stop on good terms. Ask, too, whether either of you would want to go full-time if it takes off.

If you're still choosing where to look, our list of the best free cofounder matching websites compares what each free plan includes.

Sources (read 26 October 2026): Foundinity · YC: What do people want in a co-founder? (2021) · YC Co-Founder Matching · Startup School FAQ · YC Startup Library: How to find a technical co-founder · Ask HN: YC matching for a side project? (2023) · Show HN rules · HN Search by Algolia · GummySearch: r/SideProject · GummySearch: r/cofounder · r/cofounder rules summary · Indie Hackers group page (retired, read 8 October 2026) · Devpost: open online hackathons · Devpost Help: Participants page · MLH: About · MLH: events · FoundersList: Find a Cofounder. Self-reported numbers are each organisation's own and undated unless stated.