Lemlist API Key Encoder.
Paste your Lemlist API key to get the base64-encoded value for HTTP Basic authentication. Encoded right in your browser — nothing leaves your device.
Paste your key without the colon. Encoded locally in your browser; your key is never sent or stored.
Your encoded key will appear hereUse it as Authorization: Basic <encoded> in your API requests.
How Lemlist API authentication works
The Lemlist API uses HTTP Basic authentication. Basic auth encodes a username:password pair in base64, but Lemlist expects the username to always be empty and your API key to take the place of the password.
That means the string you encode is :YourApiKey — with the leading colon kept. After base64-encoding it, you send the result in the request header:
Authorization: Basic <base64-encoded-value>
This tool does that encoding for you, locally in your browser. For the full details, see the Lemlist authentication docs.
Frequently asked questions.
Is my API key sent anywhere?
No. The encoding runs entirely in your browser using JavaScript. Your API key is never sent to a server, logged, or stored.
Why is there a leading colon before the key?
Lemlist uses HTTP Basic authentication with an empty username. In Basic auth the encoded value is “username:password”, so with an empty username it becomes “:YourApiKey” — the colon must stay.
How do I use the encoded value?
Send it in the Authorization header as “Authorization: Basic <encoded-value>” on your requests to the Lemlist API.