In APA, DOI means Digital Object Identifier. It’s a permanent, unique code used to identify a source and link to it online.

Why it matters

A DOI helps readers find the exact article, book, or report even if its web address changes later.

How it looks in APA

In APA 7, the DOI is usually written as a URL, like this:
[https://doi.org/10.xxxx/xxxxx6]

Example

A reference entry might end with a DOI instead of a regular URL when the source has one.

TL;DR

DOI = a stable online identifier for a source, and APA uses it to make citations easier to trace.