Available authentication methods: API key and OAuth 2.0.

API key

Provide your API key using the Authorization header with every request. All 2026-03-15 requests also require the Omnisend-Version header.

curl --request GET \
  --url 'https://api.omnisend.com/api/segments' \
  --header 'Authorization: Omnisend-API-Key YOUR-API-KEY' \
  --header 'Omnisend-Version: 2026-03-15'

To get your API key go to API keys section

OAuth

OAuth 2.0 is also supported using an Authorization: Bearer {access-token} header. Please refer to the OAuth page for the full flow.