You asked about Reinforcement Learning
482 people built something like it. 68 are gone.
That is 16% of the ones whose fate we could settle, against 23% across the whole register. 47 were acquired.
| Launched | What it was | Today |
|---|---|---|
| 2022-06-03 | courses.dibya.online | still up |
| 2019-01-01 | YCrct AI build AI NPCs · rct.ai | still up |
| 2024-06-01 | YCSepal AI Data Development for Advanced AI · sepalai.com | acquired |
| 2016-01-01 | YCPathmind Pathmind helps industrial engineers and simulation modelers achieve… · pathmind.com | gone |
| 2025-01-01 | YCHUD Platform and marketplace for RL environments and AI data · hud.ai | still up |
| 2025-06-01 | YCidler Hill-climb any benchmark, for any model, in any domain. · idler.ai | still up |
| 2024-06-01 | Open-Source Reinforcement Learning (RL) & Fine-tuning for LLMs. · unsloth.ai | still up |
| 2024-01-01 | Autonomously scaling environments · vibrantlabs.com | still up |
| 2025-01-01 | Reasoning Fine-Tuning · trainloop.ai | still up |
| 2023-01-01 | YCUnify Models that keep learning · unify.ai | still up |
| 2025-01-01 | YCOsmosis Reinforcement Learning (RL) for AI Agents · osmosis.ai | still up |
| 2026-06-01 | We turn company data into training data · ooakdata.com | still up |
| 2025-01-01 | Frontier Data · sherpalabs.ai | still up |
| 2026-09-01 | YCEpsilab Long horizon RL environments from real-life data · epsilab.com | still up |
| 2024-01-01 | YCJustAI Agentic Marketing Platform · getjust.ai | still up |
| 2025-09-01 | Training Data for Recursive Self-Improvement · hillclimb.com | still up |
| 2026-06-01 | YCCueBench RL post-training for science reasoning and performance engineering · cuebench.dev | still up |
| 2025-09-01 | Large-scale real-world robot & human data for embodied AI · cortexrobot.ai | still up |
| 2026-06-01 | Turns real businesses into robotics data vendors · praxisrobotics.io | still up |
| 2023-01-01 | YCVelos AI BPO for Specialty Insurance MGAs · tryvelos.com | still up |
| 2026-06-01 | We find flaws in RL environments and evals and help you fix them. · touchyapp.com | still up |
| 2025-06-01 | YCMonte Continual Learning for Agents · trymonte.ai | still up |
| 2026-01-01 | YCBrumby Robot Cowboys that Herd Cattle with AI Drones · brumby | still up |
| 2026-06-01 | YCPetrarch Advancing model capabilities for critical infrastructure · petrarch.co | still up |
| 2026-06-01 | YCCoArena The biggest crowdsourced benchmark for Computer-Use · coarena.ai | still up |
| 2026-06-01 | Autoresearch as a service: we solve your hardest measurable problems · hiloop.ai | still up |
| 2026-06-01 | YCEdotEnv Quant Neolab building self-improving agents from quant data · edotenv.com | still up |
| 2026-06-01 | YCEnact Real-world RL environments for robotics models · enact.company | still up |
| 2026-06-01 | Training the world's best AI model for quantitative finance. · prodigy.markets | still up |
| 2026-06-01 | Open source AI gateway that turns your traffic into better models · experientiallabs.ai | still up |
| 2025-06-01 | Physics-based foundation models for CAD optimization. · topological.com | still up |
| 2026-06-01 | YCFabraix The world's frontier hacker of AI agents. · fabraix.com | still up |
| 2025-09-01 | YCSylvian Specialized AI Agents. · sylvian.ai | gone |
| 2025-06-01 | YCNuntius Making Models Follow Rules. · nuntius.ai | gone |
| 2026-01-01 | Infrastructure for Autonomous Science · syntheticsciences.ai | still up |
| 2026-06-01 | YCMarkov Expert computer-use data for frontier AI labs · markovstudios.com | still up |
| 2024-01-01 | Self-improving content bank for marketing · useresonance.com | acquired |
| 2024-09-01 | YCSynth Prompt and Context Optimization for Coding Agents · usesynth.ai | still up |
| 2025-01-01 | Foundational model research · agentin.ai | still up |
| 2026-01-01 | YCAshr Enterprise post-training, monitoring, and continual learning platform · ashr.io | still up |
| 2026-06-01 | Crafting simulations for frontier lab model training · olamlabs.ai | still up |
| 2026-06-01 | YCMagma Monetize your agent's traces. · magmahq.ai | still up |
| 2026-01-01 | YCTraverse Custom models and inference, built and run for enterprises · traverse.so | still up |
| 2026-01-01 | Evals for frontier research agents · buildwithglue.com | still up |
| 2026-06-01 | YCRiften Earned intelligence for every company · riften.ai | still up |
| 2019-01-01 | Online engineering college for India. Learn technical skills & get… · skill-lync.com | still up |
| 2014-01-01 | YCCruise Self-driving cars. · getcruise.com | acquired |
| 2016-01-01 | Building humanity’s multiplanetary future. · relativityspace.com | still up |
| 2022-04-04 | heyday.xyz | still up |
| 2015-01-01 | Rebuilding healthcare with AI at the core · akidolabs.com | still up |
| 2017-06-01 | The first public safety operating system that eliminates crime. · flocksafety.com | still up |
| 2015-06-01 | YCGo1 A learning platform that enables you to train your staff or customers. · go1.com | still up |
| 2016-06-01 | YCScale AI Data-centric infrastructure to accelerate the development of AI · scale.com | still up |
| 2019-06-01 | YCTRM Labs TRM is building a safer world for billions of people. · trmlabs.com | still up |
| 2022-03-02 | huemint.com | still up |
| 2022-10-03 | continuum.xyz | unverified |
| 2018-06-01 | YCUBITS Learning Hub for companies in Latam · ubits.com | still up |
| 2006-06-01 | YCScribd World's largest online library. · scribd.com | still up |
| 2022-04-12 | damnnnn.com | gone |
| 2021-01-30 | nn.labml.ai | still up |
How this compares
Y Combinator reports its own outcomes, including acquisitions. The other two are judged by asking the domain, so they are not measured the same way and are never averaged together.
Older launches have had longer to die, so this slope is expected. A year that broke it would mean something is wrong with the checking.
The register re-probes every domain it holds. Some that answered last month stop answering. We send that list — what went quiet, and what it was — once a month. Nothing else.
How this was made. Show HN entries are every post from 2021 to 2023 with at least five points that linked to its own domain; code hosts and free hosting are excluded, because a repository outlives the effort behind it. Product Hunt entries needed 100 votes — a far higher bar, so they are the promoted top slice rather than a like-for-like sample. Both are judged by asking the domain whether it still answers: gone means it no longer resolves, refuses the connection, serves a parking page, or says plainly that it shut down. An HTTP error is not counted as gone — a server answering 404 is one somebody still pays for, and an audit of 25 gone-calls found two such sites alive with only a moved homepage. Y Combinator entries use the status YC publishes itself, which is why only those can say acquired. Squatted domains — a lapsed name now serving somebody else's site — are not detected, so these figures run slightly low.