Voting stations in Indonesia's east were the first to open, the massive exercise spanning over six thousand islands.
The most recent opinion poll taken earlier this month by the Indonesian Survey Institute suggests there's just three-point-six percent separating the front runner Joko Widodo and Prabowo Subianto.
It may take up to a month, before formal results are announced.
Presenter: Sen Lam
Speaker: Helen Brown, Indonesia correspondent, Australia Network
LAM: Helen, it's just after 7 am there. Tell us where you are and what's the mood like?
BROWN: Well, I'm actually at one Jakarta's most loveliest parks in the suburb of Menteng, which is where a lot the diplomats live.
But it also happens to be the home of Joko Widodo and his local polling booth. So they've set up a polling booth in the park and as you can imagine, Joko Widodo is one of the presidential candidates and there are many, many media here already waiting for his arrival. He's coming into vote in around an hour's time.
The mood is there's a lot of expectation today, it's a big day as you can imagine and I'd say there's more media than voters at the moment, because the polling booths haven't actually opened, they're just setting them up, but there's definitely an air of expectation, lots of local media, lots of international media here as well, just waiting for Joko Widodo's arrival.
LAM: As you say, for the moment, it seems to be more media than voters. But it is a mammoth exercise. Are the organisers expecting a huge turnout?
BROWN: They are, actually. We initially were told that there were 188-million registered voters and that's gone up to 190, which they believe is that just basically, more people are going to be turning up to vote than expected.
It is a big decision day for Indonesia, the choice they make today will determine the President for the next five years and there are two very different styles on offer and so people are going to have to make a very clear choice. And as the polling indicates, it's a very tight race.
LAM: Mmm. Sorry. Just talk us through the practicalities, talk us through the voting process. Is it fairly voter friendly, will the illiterate, for example, be able to vote?
BROWN: Ah, it is, so essentially on their ballot paper, they have two choices. It's pretty amazing, they get to directly choose the President of Indonesia, number one, which is Prabowo Subianto or number two, which is Joko Widodo. Now, I expect that even if you're illiterate, you can work out which is number one and which is number two, because there are pictures of the candidates as well and it's all in very large lettering.
Five hundred thousand polling booths have been set up around the archipelago and that would hold a total of 500-voters only, but they set up lots everywhere to give everyone a chance of getting in.
And then, aside from that logistical nightmare of setting up all those polling booths and getting the papers to them, they then afterwards, manually count the votes and this is why we won't have the official result later today, we'll have what are called the quick counts done by private polling agencies.
But it will take, it could take up a month to manually count these votes and they get them in at these little polling booths and sit down and go through them and that's just the first count of many. Once they're counted there, they're moved up to the next level, so it's agonising process that requires I think around 6 million people they've got in to run it just today.
LAM: Indeed, and Helen Brown, what's word on the street, is it still a very close race between Jokowi and Prabowo?
BROWN: Look, it's really hard to tell. The surveys here are all pointing to a very tight race.
One has come out indicating that there's been a shift to Joko Widodo. But honestly, the survey, some of them are bias, they don't have the credibility that they would in Australia, for instance, and there are some questions about even this survey rating in such a big country. Can you only poll two or three-thousand people?
But the trend seems to be the same.
We were actually at the house of Prabowo Subianto last night, where he met some foreign journalists and they're feeling very confident themselves, they say the polls are actually in their favour, but until those numbers come in, you just don't know. And this is Indonesia, Sen, so we think we might know what's going to happen, but it could completely turn upside down and we get a result we're not even expecting.