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What is an API key?
An API key is a secret code that proves to a service that a request comes from you.
- Category Building with AI
- Updated 20 Oct 2026
API key, explained simply
An API key is a long string of letters and numbers. A service gives it to you when you sign up. It works like a password for apps.
It matters because many AI tools ask for one. You paste it in so the tool can use an AI service on your account.
Usage is often billed to your account. Keep your key private so nobody else runs up your bill.
If a key leaks, delete it in your account and make a new one.
On ITG Now, our free tool guides say when a tool needs an API key and how to get one.
Related terms
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Questions people ask about API key
Is an API key free?
Getting a key is often free. Using it may cost money or have free limits.
Is it safe to share my API key?
No. Treat it like a password. Never post it in public places, such as chats or public code.
Where do I put my API key?
Many tools ask you to paste it into a settings box or an environment variable.