i3 has the following dependencies:

   "min" means minimum required version
   "lkgv" means last known good version

┌─────────────┬────────┬────────┬────────────────────────────────────────┐
│ dependency  │ min.   │ lkgv   │ URL                                    │
├─────────────┼────────┼────────┼────────────────────────────────────────┤
│ pkg-config  │ 0.25   │ 0.26   │ http://pkgconfig.freedesktop.org/      │
│ libxcb      │ 1.1.93 │ 1.7    │ http://xcb.freedesktop.org/dist/       │
│ xcb-util    │ 0.3.3  │ 0.3.8  │ http://xcb.freedesktop.org/dist/       │
│ libev       │ 4.0    │ 4.04   │ http://libev.schmorp.de/               │
│ flex        │ 2.5.35 │ 2.5.35 │ http://flex.sourceforge.net/           │
│ bison       │ 2.4.1  │ 2.4.1  │ http://www.gnu.org/software/bison/     │
│ yajl        │ 1.0.8  │ 2.0.1  │ http://lloyd.github.com/yajl/          │
│ asciidoc    │ 8.3.0  │ 8.6.4  │ http://www.methods.co.nz/asciidoc/     │
│ xmlto       │ 0.0.23 │ 0.0.23 │ http://www.methods.co.nz/asciidoc/     │
│ Pod::Simple²│ 3.22   │ 3.22   │ http://search.cpan.org/~dwheeler/Pod-Simple-3.23/
│ docbook-xml │ 4.5    │ 4.5    │ http://www.methods.co.nz/asciidoc/     │
│ libxcursor  │ 1.1.11 │ 1.1.11 │ http://ftp.x.org/pub/current/src/lib/  │
│ Xlib        │ 1.3.3  │ 1.4.3  │ http://ftp.x.org/pub/current/src/lib/  │
│ PCRE        │ 8.12   │ 8.12   │ http://www.pcre.org/                   │
│ libsn¹      │ 0.10   │ 0.12   │ http://freedesktop.org/wiki/Software/startup-notification
│ pango       │ 1.30.0 | 1.30.0 │ http://www.pango.org/                  │
│ cairo       │ 1.12.2 │ 1.12.2 │ http://cairographics.org/              │
└─────────────┴────────┴────────┴────────────────────────────────────────┘
 ¹ libsn = libstartup-notification
 ² Pod::Simple is a Perl module required for converting the testsuite
   documentation to HTML. See http://michael.stapelberg.de/cpan/#Pod::Simple

 i3bar, i3-msg, i3-input, i3-nagbar and i3-config-wizard do not introduce any
 new dependencies.

 i3-migrate-config-to-v4 is implemented in Perl, but it has no dependencies
 besides Perl 5.10.