> For the complete documentation index, see [llms.txt](https://chembl.gitbook.io/unichem/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://chembl.gitbook.io/unichem/definitions/what-is-meant-by-a-src_id-and-a-src_compound_id-in-unichem.md).

# What is meant by a 'src\_id' and a 'src\_compound\_id' in UniChem ?

## src\_id

src\_ids are integers that are unique identifiers for sources in UniChem. A list of valid src\_id's can be found either on the [sources](https://www.ebi.ac.uk/unichem/ucquery/listSources) page or by using the [web services](https://www.ebi.ac.uk/unichem/info/webservices).

## src\_compound\_id

src\_compound\_ids are the individual compound identifiers provided by each of the sources. For example 'CHEMBL12' is a src\_compound\_id from the 'chembl' source (src\_id = 1). Since src\_compound\_ids may be ambiguous across different sources, querying UniChem with a src\_compound\_id also requires the specification of a corresponding src\_id. src\_compound\_ids are dealt with in a case sensitive manner, as explained [here](https://www.ebi.ac.uk/unichem/info/inputFormats).


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