How long is Sri Lanka e-Visa valid for?

The validity of the Sri Lanka Electronic Visa (e-Visa) is 6 months from the date of issuance. The term "validity" refers to the state of an e-visa being legally acceptable in Sri Lanka, which means the e-visa can be used. When your Sri Lanka e-Visa is issued, you can use it to enter Sri Lanka within the following 6 months. After that time, your e-Visa will expire, and you will have to apply for another visa if you want to travel to Sri Lanka.

You should distinguish the difference between the time Sri Lanka e-Visa is valid for and stay for.

Sri Lanka Tourist e-Visa: This eVisa allows you to stay in Sri Lanka for sightseeing and recreational purposes. You can stay in the country for 30 days from your arrival date with a double entry.
Sri Lanka Business e-Visa: Foreigners can use this visa to participate in business meetings and negotiations conducted in Sri Lanka. It is also for visitors who want to participate in short-term training programs that do not last over one month or art, music, and religious events organized in the country. If you use this visa, you can enter Sri Lanka as many times as you want and stay here within 30 days from your date of entry.
Sri Lanka Transit e-Visa: This type of visa is issued for transit purposes only with a single entry. You can stay temporarily in Sri Lanka within 48 hours from your arrival date before taking a connecting flight to your onward destination.