A dropdown can guide entry without strictly enforcing its options. If someone can enter another value, inspect invalid-data behavior rather than assuming validation has stopped working.
Check the specific rule and range
Select the affected cell and open Data > Data validation. Confirm the rule covers that cell, then inspect its criteria and Advanced options. A copied or newly appended row may sit outside the intended rule.
Compare two cells if some rows reject the same entry and others accept it. Similar-looking dropdown chips do not prove that the underlying rules and scopes are identical.
Choose warning or rejection
Google’s dropdown guidance distinguishes rejecting values outside the list from Show a warning. A warning permits the entry while signaling that it does not match the criteria.
Use rejection when the process requires a closed vocabulary, and warning when exceptions are intentionally allowed and reviewed. Changing this policy can affect existing workflows, so coordinate it with the people responsible for the data.
Review historical exceptions separately
Try a valid option and an intentionally invalid sample in a safe test cell covered by the rule. Then inspect existing records for spelling variants, spaces, and obsolete options. A stricter setting is not evidence that every earlier value has been corrected.
Retain original entries until the appropriate owner decides how to normalize them. Do not map all unknown statuses to the first available option or erase exceptions to remove warnings. Check downstream summaries that group by the dropdown value, because a harmless-looking spelling difference can split one business category into several results even when the visible chip style appears consistent.
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.