The UK ETA processing time is usually fast, but it may vary depending on the application details.
If additional review is required, it can take up to 3 working days to receive a decision.
Processing may take longer if there are issues such as incorrect passport details, mismatched personal information, criminal records, or previous immigration history.
Therefore, if your UK trip is confirmed, it is safer to apply for a UK ETA at least 3 working days before departure.