There are 11 official candidates, 4 of them are polling around the 20% mark, the 7 others take the rest. 4 candidates so close together 1 week before the election, this has never happened since this system exists (1965). Charles de Gaulle who invented the system wasn't a visionary though, he thought he would be elected triumphally in the first round in 1965 and instead a young François Mitterrand happened and a runoff was necessary.
Official posters of the candidates :

They've been sorted from far left to far right :
Arthaud and Poutou are trotskyists, Cheminade is against finance and wants to colonize Mars, Mélenchon is old school socialist/communist/green, Hamon is the candidate of the Socialist Party and the Greens, Macron is a social-democrat without a party, calling himself both left-wing and right-wing, Lassalle is a centrist that must have drunk too much as you can't understand what he's saying, Fillon is the candidate of the right wing Les Republicains, Dupont-Aignan is a right-wing nationalist, Asselineau is a conspirationist who wants Frexit, and Le Pen is an anti-Islam nationalist.
The four who have a chance to make it to the runoff :


A few weeks ago Macron and Le Pen were at 25-26% each so they lost ground. Fillon was at 17% so he's coming back a bit, and Mélenchon has surged dramatically, helped by the inflight disintegration of Benoît Hamon.
A runoff between Le Pen and Mélenchon, thought unimaginable, is now a real possibility. Both are against the EU and want to control the French currency to devalue it, implement protectionist policies, both are closer to Putin than to the US, etc. Now that such a runoff is a real possibility polls have been conducted and Mélenchon is given as the winner.
Here are the various runoff scenarios :

Interesting times !