YAML

Anchors and Aliases

Reuse nodes with anchors, aliases, and merge keys.

By EZ4Code TeamLast updated: 2026-08-01

anchoraliasmerge

Code

defaults: &defaults
  adapter: postgres
  host: localhost

development:
  <<: *defaults
  database: dev_db

production:
  <<: *defaults
  database: prod_db
  host: db.example.com

Explanation

An anchor (&name) marks a node for reuse and an alias (*name) inserts a reference to it, avoiding duplication. The merge key (<<) merges a referenced mapping into the current one so you can override individual keys. Aliases share identity, so they cannot form cycles.