Free open source APIs
27 services, checked weekly
These free APIs are open source: besides the public service, the code is available, so you can read how it works and, if the public server is not enough, run your own copy without limits.
| Service | Category | API key | Formats | Free use |
|---|---|---|---|---|
| Pollinations.ai | Artificial intelligence | Not needed | – | Free, works without a key or sign-up; registering gives higher limits. |
| bible-api.com | Books and research | Not needed | JSON | Free and open source, no key needed. |
| Gutendex | Books and research | Not needed | JSON | Free and open source, no key needed; it is a community service without uptime guarantee, so you can host it yourself for heavy use. |
| PoetryDB | Books and research | Not needed | JSON | Free and open source, no key needed. |
| ntfy | Communication | – | – | Free on ntfy.sh, and open source so you can host it yourself. |
| Frankfurter | Currency and finance | Not needed | JSON | Free, no key needed and no usage limits. |
| Free Currency Exchange Rates API (fawazahmed0) | Currency and finance | Not needed | JSON | Free. |
| country.is | IP to location APIs | Not needed | JSON | Free and open source, no key needed. |
| ipify | IP to location APIs | Not needed | JSON | Free and open source, no key and no usage limit. |
| Nager.Date public holidays | Location Information | Not needed | JSON | Free and open source, no key needed. |
| OpenRouteService | Location Information | Needed, free | JSON | Free plan with a free API key and daily limits per service; open source, so you can also host it yourself. |
| Photon | Location Information | – | JSON | The public server at photon.komoot.io is free for fair use; for heavy use you can host Photon yourself, as it is open source. |
| Postcodes.io | Location Information | Not needed | JSON | – |
| Open-Meteo | Weather forecasts | Not needed | JSON | Free for non-commercial use; commercial use needs a paid plan. |
| wttr.in | Weather forecasts | Not needed | – | Free and open source, no key needed. |
| Iconify API | Graphics | Not needed | – | Free, no key needed; the server is open source and can be self-hosted. |
| Kroki | Chart APIs | – | – | Free public server; open source, so you can also run it yourself. |
| QuickChart | Chart APIs | – | – | Free plan with a monthly limit; paid plans for more charts. |
| DiceBear avatars | Image and photo | Not needed | XML | Free and open source, no key needed. |
| Free Dictionary API | Language and text | Not needed | JSON | Free and open source, no key needed. |
| Spaceflight News API | News feeds and APIs | Not needed | JSON | Free and open source, no key needed. |
| Dog CEO Dog API | Other | Not needed | JSON | Free and open source, no key needed. |
| Open Brewery DB | Other | Not needed | JSON | Free and open source, no key needed. |
| PokéAPI | Other | Not needed | JSON | Free and open source, no key needed. |
| Nu HTML Checker (W3C) | Data validators | – | – | Free and open source; for heavy use, run your own copy of the checker. |
| OpenIBAN | Data validators | Not needed | JSON | Free and open source, no key needed. |
| httpbin | Testing and mock data | Not needed | JSON | Free and open source, no key needed; you can also run it yourself in Docker. |