Authentication

The authentication is done passing your API token associated with your pro plan as x-api-key request header.
curl -H 'x-api-key: YOUR_API_TOKEN' https://instagram.com/p/BvDTdWdnzkj
You can ensure your authentication is done correctly checking the x-pricing-plan header on the response.
curl -I -s -X GET https://api.microlink.io?url=https://instagram.com/p/BvDTdWdnzkj&apiKey=MyApiToken | grep -i "x-pricing-plan"
If you need to consume the API from a frontend side (e.g, from a website), don't attach your API token directly in your client code: It will easy to a visitor leak it and consume your API quota without consent.
Instead, you need to setup a mechanism to just allow consume your token for a whitelist of trusted domains. Check for that purpose.

Authentication

The authentication is done passing your API token associated with your pro plan as x-api-key request header.
curl -H 'x-api-key: YOUR_API_TOKEN' https://instagram.com/p/BvDTdWdnzkj
You can ensure your authentication is done correctly checking the x-pricing-plan header on the response.
curl -I -s -X GET https://api.microlink.io?url=https://instagram.com/p/BvDTdWdnzkj&apiKey=MyApiToken | grep -i "x-pricing-plan"
If you need to consume the API from a frontend side (e.g, from a website), don't attach your API token directly in your client code: It will easy to a visitor leak it and consume your API quota without consent.
Instead, you need to setup a mechanism to just allow consume your token for a whitelist of trusted domains. Check for that purpose.