The sync mode keeps fields synchronized across all language stores on every save, while remapping relational references to each language’s equivalent when possible.
At save time
- Propagates every save to all sibling language stores (source can be default or non-default language).
- Applies Polylang Pro mapping for relational fields, so values are remapped per target language when possible. Examples: relationship and post_object fields map to translated post IDs, taxonomy fields map to translated term IDs, and image, file, and gallery fields map to translated media.
- Container parents can also be forced to sync when descendants require sync or translate propagation.
During import
- Copies source value to the default-language store only when the default-language value is empty.
- Propagates immediately to targets.
- Uses the same relational mapping logic as save time.
When to use
Use sync sparingly, only when fields must stay synchronized across languages while still mapping relational references to each language equivalent. Good for shared IDs, technical flags, and global configuration values. See Field translation overview and Import from default ACF options for sync overwrite behavior during import.