The CLIC Test Fa­cil­i­ty 3 (CTF3) is being built and com­mis­sioned by an in­ter­na­tion­al col­lab­o­ra­tion in order to test the fea­si­bil­i­ty of the pro­posed Com­pact Lin­ear Col­lid­er (CLIC) two-beam ac­cel­er­a­tion scheme. The mon­i­tor­ing and con­trol of the bunch length through­out the CTF3 com­plex is im­por­tant since this af­fects the ef­fi­cien­cy and the sta­bil­i­ty of the RF power pro­duc­tion pro­cess. Bunch length di­ag­nos­tics there­fore form an es­sen­tial com­po­nent of the beam in­stru­men­ta­tion at CTF3. This paper pre­sents and com­pares lon­gi­tu­di­nal pro­file mea­sure­ments based on trans­verse RF de­flec­tors, Streak cam­era and non-de­struc­tive mi­crowave spec­trom­e­try tech­niques.