Open-source alternatives to the SaaS a startup would otherwise pay for

The frame Most of what an early startup pays for has a mature open-source version — often built by a company that sells hosting for the same code. You can self-host it, or just run it locally while you're small and move to their paid cloud later if it earns its keep. Either way you start out owning your data instead of renting access to it. Two honest caveats before you lean on any of this: · Self-hosting is not free. It is a server, updates, backups and an on-call you, traded against a monthly bill. Below a certain size the paid cloud tier is the right call — the value here is optionality, not saving twenty dollars a month. · Check the licence. "Open source" now covers MIT (do what you like), AGPL (you must publish your changes if you offer it as a service), and "fair-code" / source-available licences that limit running it as a competing service. For anything you build a product on, read the LICENSE file before you commit — n8n, for instance, is fair-code, not OSI open source. The starter set The list leads with Runa Capital's awesome-oss-alternatives, the maintained index — 200+ open-source companies mapped to the paid tool they replace. The rest are specific ones worth knowing by name: · Supabase — the fastest way to a Postgres database with auth, file storage and realtime already wired. This platform runs on it. · PostHog — product analytics, session replay and feature flags in one. Also what this platform uses. · Metabase — point it at your database and non-engineers can build their own dashboards. · Cal.com and Documenso — scheduling and e-signatures, the two "just use the SaaS" tools that are now genuinely replaceable. · Chatwoot — a shared support inbox and website chat widget. · Twenty — a CRM that doesn't feel like it's from 2009. · Trigger.dev — background jobs, retries and cron, defined in your own codebase. · Formbricks — surveys and in-app feedback, which pairs with actually talking to users. · n8n — connect APIs and automate the glue work; the open alternative to Zapier. How to contribute back If one of these becomes load-bearing for you, the highest-leverage thing you can do is file good bug reports and fix the small things that annoy you. A merged one-line docs fix is a real open-source contribution and takes an afternoon. Maintainers remember the founders who showed up.