Categories with many maintained implementations and a dominant leader. Building here means fighting free software with a full-time team.
A crowded category has dozens of maintained free alternatives and one project with an order-of-magnitude lead. You can still win, but only with a wedge the incumbents structurally cannot copy. This view holds 11 categories, refreshed August 2026.
76 projects · 40 maintained · leader revealjs (72k)
Free, maintained alternatives already dominate this category.
100 projects · 58 maintained · leader Dify.ai (153k)
Free, maintained alternatives already dominate this category.
177 projects · 100 maintained · leader Mastodon (50k)
Free, maintained alternatives already dominate this category.
62 projects · 36 maintained · leader Jellyfin (56k)
Free, maintained alternatives already dominate this category.
44 projects · 29 maintained · leader Strapi (73k)
Free, maintained alternatives already dominate this category.
58 projects · 28 maintained · leader copyparty (46k)
Free, maintained alternatives already dominate this category.
42 projects · 27 maintained · leader HyperSwitch (43k)
Free, maintained alternatives already dominate this category.
41 projects · 22 maintained · leader Stirling-PDF (90k)
Free, maintained alternatives already dominate this category.
40 projects · 20 maintained · leader Sunshine (40k)
Free, maintained alternatives already dominate this category.
34 projects · 15 maintained · leader n8n (201k)
Free, maintained alternatives already dominate this category.
38 projects · 18 maintained · leader Superset (74k)
Free, maintained alternatives already dominate this category.
Existence is not competition. A project competes with you only if it is maintained, findable, deployable by your buyer and licensed for their use. Most projects fail at least one of those tests. Run all four before you shelve an idea — or before you assume you have a clear run.
Stars are a lifetime counter with no decay, so a project abandoned in 2022 still looks like a leader in 2026. In this dataset 149 projects are dormant, abandoned or archived, and several of them sit in the top decile by stars. Sort by momentum and commit activity instead — popularity tells you the project was once interesting, maintenance tells you whether it will still be there when your customer needs a bug fixed.
When a prospect says 'we could just self-host the free one', they are usually comparing your price against zero. The real comparison is your price against hosting, upgrades, backups, security patching, integration work and the engineer hours behind all of it. Quantifying that number is the single most effective response to a free-alternative objection — and it is more persuasive coming with a spreadsheet than with a feature list.
Founders treat licensing as a legal footnote and then discover it dictates strategy. Permissive licences allow closed commercial forks, which is why so many managed services exist around MIT and Apache projects — and also why your differentiation cannot be the code itself. Copyleft licences, especially AGPL, remove the closed-wrapper option entirely, which reduces competition but restricts you too. Source-available licences exist precisely to stop the wrapper business.
Search this database by category and by the commercial product you would replace. It covers 1665 projects across 130 categories, each mapped to the paid tool it substitutes. If your category shows a "Crowded" verdict, a maintained free version almost certainly exists and your positioning has to account for it.
No. It means free is your price anchor. Plenty of large companies were built next to a good open-source project — the ones that failed were the ones selling the same job at a price the free tool made indefensible. Find the part of the job the project deliberately does not do, and sell that.
Each category gets a 0–100 score built from three inputs: how many implementations exist, what share of them are still actively maintained, and how far ahead the leading project is compared with the category median. 62+ is Crowded, 38–61 Contested, under 38 Open. 11 categories are Crowded and 88 are Open.
A project has momentum when it committed code in most of the last twelve months, shipped a release recently and is not archived. 736 of 1665 projects qualify. This is the single most useful filter here — it strips out the popular-but-dead repositories that make a category look more competitive than it is.
It depends entirely on the licence. MIT, Apache and BSD let you build and sell closed products on top. GPL and AGPL require derivative work to stay open, and AGPL extends that to network use, which blocks most SaaS wrappers. BSL, SSPL and Commons Clause are source-available, not open source, and usually restrict competing commercial use outright.
IdeaProof scores your idea against live competitors, market size and 1,000+ documented startup failures in about two minutes.