According to election law, any election campaign is forbidden 24 hours before the polls open.
Reformist Massoud Pezeshkian and principlist Saeed Jalili campaigned for five days from Sunday, with two televised debates, text messages, online face-off, and street campaigns which peaked on Wednesday evening.
Pezeshkian runs on a platform of making an overhaul in economy, social reforms, and foreign policy détente.
Jalili believes the solutions to the persisting problems in the country lie at home, and his administration would take advantage of the domestic expertise and resources.
Over 10.4 million out of the 24.5 million people who took part in the first round voted for Pezeshkian and Jalili received 9.4 million votes.
Polls will open at 8 am on Friday for over 61 million eligible voters across the country to fill the top executive post left vacant after former president Ebrahim Raisi and his entourage died in a helicopter crash in May.
Like the first round, over 58 thousand polling stations in Iran and over 344 stations outside the country will be set up to facilitate the voting, Mohsen Eslami, the spokesman for the Election Headquarters told the state broadcaster (IRIB).
Eslami said those who did not take part in the first round can cast their ballots in the run off. He added the final results would be announced on Saturday at noon.
