# DNAnexus API

The DNAnexus Platform can be accessed programmatically via an API using HTTP requests to the DNAnexus API servers. Each API method may receive zero or more arguments as fields in a JSON string, and may return some results, always as a JSON string. For specifics on how to call an API method, see [Protocols](https://documentation.dnanexus.com/developer/api/protocols) and [Authentication](https://documentation.dnanexus.com/developer/api/authentication).

To skip to a particular API method, you can look it up in the [Directory of API Methods](https://documentation.dnanexus.com/developer/api/api-directory).

## The API methods

You can expect URLs corresponding to API methods to be always of the following form:

```
/subject/methodname
```

Where the subject can be one of the following:

1. The word "system", for system-wide methods. These methods are for search functionality, as well as other utilities that do not fall under a specific entity class. **Example**: `/system/findDataObjects` takes in query parameters and returns a list of matching data objects.
2. An entity class for which a new instance may be created **Example**: `/file/new` creates a new file data object that can be written to
3. An entity ID, for methods that act on existing instances, where the method name is a verb acting on the object. **Example**: `/file-xxxx/close` closes the file object with ID "file-xxxx"

### Data Types

When describing an input or output to an API method, the data type is given in **bold**. For example:

* `tags` **array of strings** Tags to be added to the file.

The following data types are used: **number, integer, timestamp, string, boolean, null, array, mapping**.

* **number, string, boolean, null, array** correspond to the [JSON data types](https://en.wikipedia.org/wiki/JSON#Data_types) of the same name.
* **integer** is an integer JSON number
* **mapping** is a [JSON object](https://en.wikipedia.org/wiki/JSON#Data_types).
* **timestamp** is an integer JSON number representing the number of milliseconds since the [Unix epoch](https://en.wikipedia.org/wiki/Unix_time) (UTC).

## Concepts

The following concepts in the DNAnexus API affect the operation of many API methods:

* [Regions](https://documentation.dnanexus.com/developer/api/regions)