# API key

CEFR C1 · Compound

Source: https://englishreference.com/word/api-key
Updated: 2026-08-15

## Definition

a secret code that lets one computer program talk to another. You use it like a password to prove who you are when you want to get data from a website or service.

For teachers: a unique identifier used to authenticate a user, developer, or calling program to an application programming interface. It serves as a security token to track and control how the interface is being used.

## Examples

- You need an API key to use the weather data.
- The developer had to generate a new API key after accidentally sharing the old one in a public code repository.
- To prevent unauthorized access and manage rate limits, the service provider requires a valid API key for every request sent to their server.

## Pitfalls

- Not "I put my API key in the public code." but "I kept my API key in a private file." — API keys are sensitive credentials; they should never be hard-coded into public files where others can steal them.

## Usage notes

- Often treated as a single noun phrase; typically requires 'a' or 'the' in singular form.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.