The talk will present the latest achievements in ultrashort pulse fiber laser technology and its application to high harmonic generation. A state-of-the-art Yb-based fiber laser system delivering up to 1 mJ pulse energy, 500 fs pulse duration at up to 50 kHz repetition rate is employed for the experiments. Additional pulse shortening to 45 fs duration has been achieved by subsequent hollow fiber compression. High harmonics have been generated in Argon up to the 59th order (17.5 nm). In addition, an average power of 3.2 µW (1012 Photons/s) has been measured for the strongest harmonic H21 (49 nm) generated in Krypton. The fiber laser system has also been employed as pump laser for a few-cycle OPCPA system. Such an OPCPA system delivers sub-5 fs pulses and up to 100 µJ pulse energy suitable for isolated attosecond pulse generation. Finally the scalability of the presented approaches to higher average powers and megahertz repetition rates will be discussed.