Uploaded August 2020 | Updated September 2026, 10 hours ago
What is idempotency? An API call or operation is idempotent if it has the same result no matter how many times it is applied.
Square APIs require idempotency keys to protect against accidental duplicate calls when duplicate calls can have negative consequences (for example, charging a credit card twice). For example, suppose you make a successful CreatePayment request, but your connection fails before you receive success confirmation. If you make the exact same request again, the endpoint knows it is a duplicate request and does not charge the card a second time. The result of your duplicate CreatePayment request is the same as if you had only made the request once.
Idempotency keys can be anything, but they need to be unique. Virtually all popular programming languages provide a function for generating unique strings. We have a more in-depth video linked below that covers more about idempotency if you’re interested in learning more.
The Sandbox Show Idempotency: youtube.com/watch?v=Hx8UdQx_4bE
Square Developer Forums – developer.squareup.com/forums
Square Developer Community – https://squ.re/slack
Square Developer Twitter – twitter.com/squaredev
Square Developer Blog – developer.squareup.com/blog
What is idempotency? An API call or operation is idempotent if it has the same result no matter how many times it is applied.
Square APIs require idempotency keys to protect against accidental duplicate calls when duplicate calls can have negative consequences (for example, charging a credit card twice). For example, suppose you make a successful CreatePayment request, but your connection fails before you receive success confirmation. If you make the exact same request again, the endpoint knows it is a duplicate request and does not charge the card a second time. The result of your duplicate CreatePayment request is the same as if you had only made the request once.
Idempotency keys can be anything, but they need to be unique. Virtually all popular programming languages provide a function for generating unique strings. We have a more in-depth video linked below that covers more about idempotency if you’re interested in learning more.
The Sandbox Show Idempotency: youtube.com/watch?v=Hx8UdQx_4bE
Square Developer Forums – developer.squareup.com/forums
Square Developer Community – https://squ.re/slack
Square Developer Twitter – twitter.com/squaredev
Square Developer Blog – developer.squareup.com/blog
