An EVW allows travelers from EVW eligible countries to visit the UK for tourism and business purposes for up to six months during the visa validity period.
To qualify for an EVW, applicants must hold a valid passport from an EVW eligible country and be seeking a one-time entry for a designated purpose. However, applicants with a criminal conviction may not able to eligible for an EVW application and may be eligible to apply for a Visitor Visa instead.
It is important to ensure that all the personal details provided in your EVW application are exactly as they appear in your passport. If your EVW application contains any errors, it may affect your ability to travel to the UK.
https://www.travelvisauk.co.uk/electronic_visa_waiver/