We determine the stellar population properties - age, metallicity, dust reddening, stellar mass and the star formation history - for all spectra classified as galaxies that were published by the Sloan Digital Sky Survey (SDSS data release 14) and by the DEEP2 (data release 4) galaxy surveys. We perform full spectral fitting on individual spectra, making use of high spectral resolution stellar population models. Calculations are carried out for several choices of the model input, including three stellar initial mass functions and three input stellar libraries to the models. We study the accuracy of parameter derivation, in particular the stellar mass, as a function of the signal-to-noise of the galaxy spectra. We find that at low redshift, a signal to noise ratio per pixel around 20 (5) allows a statistical accuracy on $\log_{10}(M^{*}/M_{\odot})$ of 0.2 (0.4) dex, for the Chabrier IMF. For the first time, we study DEEP2 galaxies selected by their \OII luminosity in the redshift range $0.83Comment: 41 pages, 22 figures, submitted to A&A. Results are available here https://firefly.mpe.mpg.de/v1_1_0/ or here http://www.sdss.org/dr14/spectro/eboss-firefly-value-added-catalog/