Chad or Romania? Indonesia or Monaco? Pick the right flag out of its look-alikes — after each answer you see what actually differs.
Practically identical vertical blue-yellow-red: Chad's blue is a shade darker. Chad is in Africa, Romania in Europe.
Blue-yellow-red with a coat of arms in the middle: Andorra's shield has two red cows, Moldova's an eagle.
Indonesia and Monaco are both red over white (Monaco's flag is squarer). Poland is the other way round: white over red.
Red-white-blue stripes: Luxembourg's blue is a light sky blue, the Netherlands' a dark blue.
Ireland: green-white-orange. Ivory Coast: the mirror image, orange-white-green. Italy: green-white-red.
Guinea reads red-yellow-green; Mali is green-yellow-red; Senegal is Mali's flag plus a green star.
Colombia and Ecuador have a double-width yellow band — Ecuador adds its coat of arms. Venezuela has equal bands and an arc of eight stars.
Both blue with the Union Jack and the Southern Cross: Australia's stars are white (plus a large seven-pointed star), New Zealand's are red.
White-blue-red: Russia has no emblem; Slovakia's shield shows a white double cross; Slovenia's shows Mount Triglav, set higher.
Nordic crosses: Norway is red with a blue cross, Iceland is blue with a red cross.
Blue-white-blue: Honduras has five blue stars; Nicaragua and El Salvador have a triangle emblem — Nicaragua's has a rainbow.
White serrated band at the hoist: Qatar is maroon with nine points, Bahrain is red with five.
Black-white-green with a red triangle: Jordan's triangle carries a white seven-pointed star, Sudan's has none.
Red-white-black: Egypt has a golden eagle, Iraq green Arabic script, Yemen nothing at all.
Green-red-yellow vs green-yellow-red, both with a star: Cameroon's star is yellow on red, Senegal's is green on yellow.
Orange-white-green stripes: India has a blue wheel in the centre, Niger an orange disc — and Niger's flag is almost square.
Red-white-red: Austria's stripes are equal and bright red; Latvia's red is dark carmine and the white stripe is thin.
Blue over red: Haiti has a coat of arms on a white panel, Liechtenstein a gold crown in the top corner.
Red-white stripes with a blue canton: the United States has 13 stripes and 50 stars, Liberia 11 stripes and a single star.
Horizontal tricolours: Hungary is red-white-green from the top, Bulgaria white-green-red.
Lithuania is yellow-green-red; Bolivia red-yellow-green; Ghana red-yellow-green with a black star.
Chad and Romania: the same vertical blue, yellow and red, differing only in the shade of blue. Indonesia and Monaco are a close second — both red over white.
Neighbours often share history and symbolism: pan-African green, yellow and red, pan-Arab red, white, black and green, the Union Jack on former British colonies. Simple tricolours also leave few combinations.
Try the world flag quiz or a region — wrong answers there are also taken from neighbouring countries.