UK ETA applications are recommended to be submitted before travelling to the UK.
Although many applicants may receive a decision quickly, it is recommended to apply at least 3 working days before travelling to the UK in case additional review is required.
As weekends or public holidays may affect processing times, it is safer to apply well in advance of your flight departure date.
Travellers who need a UK ETA should travel to the UK after receiving the approval email, as departing without checking the approval status may cause issues with boarding or entry procedures.