The canonical FLTK web page is located at www.fltk.org.

From there, you can find a lot of useful resources:

• Downloads
• Documentation
• User Contributed Links
  • External Documentation
  • Software and Widgets
  • Webpages about FLTK
• Language Bindings
  • Rust: fltk-rs, very active, great community
  • Python: pyFLTK, very active
  • Zig: zfltk, active
  • C: cfltk, great base for other bindings
  • Lua, FLTK 1.3, inactive
  • Ruby, FLTK 1.1, inactive
  • Haskell, outdated
  • Tcl, outdated