What is the AngularJS digest cycle and how does it work internally?

Updated Apr 28, 2026

Short answer

The digest cycle checks watchers and updates the view when model data changes.

Deep explanation

AngularJS uses dirty checking via the digest cycle. It iterates over all watchers, compares old and new values, and updates the DOM if changes are detected. This loop runs until no changes are found or a max iteration limit is reached (10 iterations) to prevent infinite loops.

Real-world example

Updating UI when a user types into an input field bound with ngModel.

Common mistakes

  • Too many watchers causing performance issues
  • triggering infinite digest loops.

Follow-up questions

  • What is dirty checking?
  • Why max 10 iterations?

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