This page aims to document the Unicode coverage of all the fonts (including non-free ones) in Debian. It was created using fontforge, font-manager and gucharmap. You should also read the DebianInstaller/GUIFonts page to find out about the fonts used by the installer.
Please add any fonts which might fill in some of these blocks to the Fonts/Missing page.
TODO: automatically create this page based on the latest unicode-data package as well as all fonts in Debian unstable, using the fonts review:
https://pkg-fonts.alioth.debian.org/review/
Quick test
Firefox seems to render all Wikipedia languages:
http://meta.wikimedia.org/wiki/List_of_Wikipedias
https://phabricator.wikimedia.org/diffusion/MW/browse/master/languages/data/Names.php
Incomplete blocks
With missing characters mentioned, most of these are available as bitmap glyphs in Unifont or Unifont Upper.
Bengali: U+09FC and U+09FD
Combining diacritical marks supplement: U+1DF6 to U+1DF9
Elbasan: U+10500 and U+10502 to U+10527
Grantha: U+11300 to U+11302, U+11305 to U+1130C, U+1130F, U+11310, U+11313 to U+1132B, U+1132A to U+11330, U+11332, U+11333, U+11335 to U+11339, U+1133D to U+11344, U+11347, U+11348, U+1134B to U+1134D, U+11350, U+11357, U+1135D to U+11363, U+11366 to U+1136C and U+11370 to U+11374
Gujarati: U+0AFA to U+0AFF
Ideographic symbols and punctuation U+16FE1
Kannada: U+0C80
Khojki: U+1123E
Limbu: U+191D to U+191E
Malayalam: U+0D00, U+0D3B and U+0D3C
Old Hungarian: U+10C81, U+10C89, U+10C8B, U+10C90 to U+10C92, U+10C94 to U+10C98, U+10C9D to U+10C9F, U+10CA1, U+10CA8, U+10CA9, U+10CAC, U+10CC0 to U+10CF2 and U+10CFA to U+10CFF
Old Permic: U+10352, U+10353, U+1035A to U+1035E, U+10363 to U+10365, U+10368 to U+1036B and U+10371 to U+1037A
Tangut U+17002 to U+17004, U+17006 to U+1702F, U+17032 to U+17037 and U+17039 to U+187EC
Tangut components U+1880C to U+1880F, U+18811, U+18813, U+18816 to U+18818, U+1881C to U+1881F, U+18825, U+18826, U+18829, U+1882E to U+18830, U+18834 to U+1883C, U+1883E to U+1884C, U+1884E to U+18852, U+18857, U+18859, U+1885A, U+1885D, U+1885E, U+18860, U+18865, U+18867, U+18868, U+1886B to U+1886E, U+18870 to U+1887C, U+1887E to U+18881, U+18883 to U+1889B, U+1889D to U+188AF, U+188B1 to U+188C6, U+188C8 to U+188D6, U+188D9 to U+188E8, U+188EA to U+18919, U+1891E, U+18921 to U+18942, U+18946 to U+18959, U+1895B to U+18975, U+18977 to U+18AD4 and U+18AD6 to U+18AF2
Vedic extensions U+1CF7
Completely empty blocks
Most of these blocks have bitmap glyphs available in Unifont or Unifont Upper.
Ahom (U+11700...)
Bassa Vah (U+16AD0...)
Bhaiksuki (U+11C00...)
Caucasian Albanian (U+10530...)
Duployan (U+1BC00...)
Hatran (U+108E0...)
Khojki (U+11200...)
Khudawadi (U+112B0...)
Mahajani (U+11150...)
Manichaean (U+10AC0...)
Marchen (U+11C70...)
Masaram Gondi (U+11D00...)
Mende Kikakui (U+1E800...)
Miao (U+16F00...)
Modi (U+11600...)
Mongolian supplement (U+11660...)
Mro (U+16A40...)
Multani (U+11280...)
Nabataean (U+10880...)
Newa (U+11400...)
Nushu (U+1B170...)
Old North Arabian (U+10A80...)
Pahawh Hmong (U+16B00...)
Palmyrene (U+10860...)
Pau Cin Hau (U+11AC0...)
Psalter Pahlavi (U+10B80...)
Sharada (U+11180...)
Siddham (U+11580...)
Sora Sompeng (U+110D0...)
Soyombo (U+11A50...)
Sutton signwriting (U+1D800...)
Syriac supplement (U+0860...)
Takri (U+11680...)
Tirhuta (U+11480...)
Warang Citi (U+118A0...)
Zanabazar square (U+11A00...)
Some conscripts in the ConScript Unicode Registry (such as Klingon, Tengwar and Visible speech) have bitmap glyphs available in Unifont CSUR.