Field masks in the Google Slides API control which properties a request returns or updates. They help keep reads efficient and changes narrow. A read mask and an update mask have different roles, so use the appropriate one rather than assuming a shorter response also limits what a later write can change.
Limit read responses
For a presentation read, use the fields URL parameter to request only the needed resource fields. Google’s guide shows selecting object IDs, sizes, and transforms from page elements. Keep enough information to identify the intended objects accurately.
Limit update properties
For an update request inside presentations.batchUpdate, list the specific properties being changed in that request’s field mask. Fields outside the mask retain their current values. Google’s guidance also warns that including a field in the mask while omitting its updated value can clear that field.
Avoid a wildcard mask in production when only a few properties should change. The official guide notes that future API additions and read-only fields can make broad wildcard behavior undesirable.
Verify preservation as well as change
Test on a disposable presentation and read back both the intended property and important neighboring properties. Open the slide to inspect appearance after the update. Keep a record of the narrow mask used so later maintainers understand the intended scope. A valid mask is not proof that you selected the correct object; combine it with current resource identification and a visual check of the final presentation. Compare before and after values.
References
Reviewed against the linked official product guidance on November 3, 2026. Features, limits, screen labels, and access can vary by account, platform, region, and organization policy.