# Versioning

The Mailjet API is spread under 3 versions.

The Email API is available under V3 (URL: `https://api.mailjet.com/V3/`). This includes all REST API resources (`https://api.mailjet.com/V3/REST`) and one transactional API resource - `https://api.mailjet.com/V3/send`.

Mailjet offers also a second transactional API under V3.1 (URL: `https://api.mailjet.com/V3.1/send`), which includes advanced error management.

The Content API is currently under V1 (URL: `https://api.mailjet.com/v1/`).

One of the main differences between the V3 and V1 versions is a change in authentication:

- V3s are using basic authentication with your public and secret API keys.
- V1 leverages a token authentication.


The URL paths for every API resource can be found in the API reference under the respective resource name.