# Existing fetchers

To learn how to use dbnomics-toolbox, you may be interested by reading the source code of existing fetchers.

All the fetchers of DBnomics are open-source and available on [GitLab](https://git.nomics.world/dbnomics-fetchers). You can browse the source code of each fetcher, however not all the fetchers use dbnomics-toolbox.

Here is a selection of fetchers that use dbnomics-toolbox as a foundation,
sorted by increasing complexity:

| Fetcher | Approach | Best for learning... |
| --- | --- | --- |
| [abc-fetcher](https://git.nomics.world/dbnomics-fetchers/abc-fetcher) (dummy) | CSV files (mock) | the simplest base pattern — JSON catalog, pandas conversion, `FetcherDefinition` public API. Used in the [](tutorial/index). Start here. |
| [cwd-fetcher](https://git.nomics.world/dbnomics-fetchers/cwd-fetcher) | Paginated JSON API | how to consume a paginated API with `PageResourceGroup` and process JSON datasets without SDMX. |
| [eurostat-fetcher](https://git.nomics.world/dbnomics-fetchers/eurostat-fetcher) | SDMX 2.1 REST API | how to extend the SDMX base classes (`BaseSdmxDownloader`, `BaseSdmxConverter`) for a standard provider. The reference SDMX fetcher. |
| [oecd-fetcher](https://git.nomics.world/dbnomics-fetchers/oecd-fetcher) | SDMX 2.1 + rate limiting | how to handle API quotas (20 req/min), configure exponential backoff, add provider-specific CLI arguments, and post-process XML/SDMX files. |
| [ons-fetcher](https://git.nomics.world/dbnomics-fetchers/ons-fetcher) | Website scraping | how to scrape HTML with BeautifulSoup, build a category tree from a website structure, and extract CSV links when no API is available. |