You will generally need a valid passport with at least six months of validity beyond your intended date of departure from the transit country.
Most countries have specific visa application forms that you must fill out accurately and completely. These forms can usually be downloaded from the website of the embassy or consulate of the transit country.
You will need to provide proof of your flight itinerary, including details of your entry and exit from the transit country.
If you are traveling to a country that requires a visa, you may need to show proof of that visa or a visa application for that destination.
There is typically a fee associated with applying for a transit visa. Be prepared to pay this fee, which can vary in amount.
Some countries may require recent passport-sized photographs as part of the visa application.
In some cases, you may be required to show proof of travel insurance that covers medical emergencies and other unforeseen events.
If your layover is extended and you plan to stay in a hotel during your transit, it may be necessary to provide a hotel reservation.
Depending on the country and your circumstances, you may need a letter of invitation from a host or a company in the transit country.
Some countries may ask for evidence that you have enough money to cover your expenses during the transit period.
In light of health concerns, especially due to pandemics, some countries may require travelers to complete health declaration forms.