21st alternatives
TL;DR: 12 companies doing similar work to 21st in B2B, ranked by how closely they match what 21st actually does — not just by category.
How this list was built: every company here is Y Combinator-backed and shares at least one category with 21st. They are scored on how closely their own description overlaps with 21st's, and all facts shown come from the YC company records — nothing is estimated.
What are the best alternatives to 21st?
| Alternative | What it does | Batch | Team | Status |
|---|---|---|---|---|
| Eivod | — | Summer 2007 | 51 | Inactive |
| Stackq | — | Summer 2009 | — | Inactive |
| BitSample | — | Winter 2008 | — | Inactive |
| Brushes | iPad drawing software. | Summer 2010 | — | Inactive |
| Fithub | — | Winter 2010 | — | Inactive |
| Insoshi | — | Winter 2008 | — | Inactive |
| Atrisa | AI Agents for Analog Circuit Design | Spring 2026 | 3 | Active |
| SolidStage | Sysadmin as a service. We make deploying, configuring, monitoring,… | Winter 2012 | — | Inactive |
| Audobox | Audobox is a developer and user friendly tool for in-app feedback. | Summer 2013 | — | Inactive |
| Wit.ai | Natural Language for Developers --Wit is an API that makes it easy… | Winter 2014 | 11 | Acquired |
| Interstate | Create & Share Product Roadmaps | Summer 2011 | 2 | Inactive |
| Hoplite | Effortlessly deploy cloud software factories. | Summer 2026 | 2 | Active |
Is 21st still active?
21st is still operating, so switching is a choice rather than a forced migration. Compare on fit and price rather than urgency.
How was this list put together?
Every company here is Y Combinator-backed and shares at least one category with 21st. They are then ranked on how closely their own description overlaps with 21st's, so the closest matches come first rather than whoever happens to share a tag.