Regional borders. The shading is derived from Natural Earth 1:10m administrative boundaries: each of the 2,034 provinces, governorates and islands in the area was assigned individually to the historical geography of Ottoman provinces (eyalet/sancak) — Turkey's 81 provinces, Romania's 42 counties, Libya's 22 districts and the Greek islands were matched one by one. Because administrative units tile the land without gaps, no gaps appear between regions and the coastlines are real. The price is that modern provinces do not fit historical borders exactly. Places that never came under Ottoman rule — Najd, the Rub' al Khali, the deep Sahara, inner Sudan, Hadramawt, Venetian Dalmatia, eastern Georgia — were deliberately left out.
Area figures and the measure used. What is measured here is land area: sea, inland water and “spheres of influence” are not counted. The value of Turkey's 18 regions is the sum of actual provincial areas, which is why the last row gives 779,000 km² — the Turkish General Directorate of Mapping's provincial dataset gives a total of 780,043 km² for Turkey, a match within 0.1%. (The projected area used in international comparisons is 783,562 km²; the true surface area including lakes and relief is 814,578 km².) For the other regions a historical estimate was used rather than modern provincial area, because in the desert modern provincial borders extend far beyond actual Ottoman control. Since every territorial change is dated to the year, figures are read from the real year-by-year curve; a sultan's gains are not counted as if all were held at the same time. Results: 5.13 million km² in 1683, and the largest extent of 5.54 million km² in 1590 (under Murad III) — consistent with the 5.0–5.6 million km² range given for the peak in the international literature. Vassal khanates and provinces (Crimea, Transylvania, Wallachia-Moldavia, Algiers) are counted as full territory; places that became autonomous but remained legally attached are subtracted in the year of their legal loss, not the year they broke away.
Why it does not say 19.9 million km². The figures 19,902,191 km² (1595) and “24 million km² including spheres of influence” (1699), often circulated in Turkey, are not from any state publication; they come from Yılmaz Öztuna's popular work Türkiye Tarihi and are wrongly attributed to the State Archives on social media. They are inconsistent as land area: 19.9 million km² is larger than Russia (17.1 million) and about 13% of all land on Earth, so they evidently include seas, nominal claims and protectorates. No official table giving territory sultan by sultan was found in publications of the Turkish Historical Society, the Directorate of State Archives or Ministry of Education textbooks; the site therefore makes its own calculation with a clearly defined measure (land area), and every region's value can be traced in the table.
Colours, battles and portraits. Held territory is blue, gained is yellow, lost is red with hatching; a region gained and lost within the same reign appears as red with yellow hatching. The hatching is a second channel: the three tones were tested for colour-blind distinguishability (ΔE 19.8 for the worst pair), and the red–green pair is never used. Each territorial change is listed with the battle, campaign or treaty that brought it. Battles are marked on the map with red dots and treaties with blue ones. The portraits are public-domain works from Wikipedia / Wikimedia Commons — the sultan series of the Veronese school, Bellini, Vanmour, John Young and Kapıdağlı, and Ottoman miniatures. Birth years not known precisely are marked with ~.