Context : Observations have discovered numerous giant molecular filaments ( GMFs ) in the Milky Way .
Their role in the Galactic star formation and Galaxy-scale evolution of dense gas is unknown .

Aims : We investigate systematically the star-forming content of all currently known GMFs .
This allows us to estimate the star formation rates ( SFRs ) of the GMFs and to establish relationships between the SFRs and the GMF properties .

Methods : We identify and classify the young stellar object ( YSO ) population of each GMF using multi-wavelength photometry from near- to far-infrared .
We estimate the total SFRs assuming a universal and fully sampled initial mass function and luminosity function .

Results : We uniformly estimate the physical properties of 57 GMFs .
The GMFs show correlations between the ^ { 13 } CO line width , mass , and size , similar to Larson ’ s relations .
We identify 36 394 infrared excess sources in 57 GMFs and obtain SFRs for 46 GMFs .
The median SFR surface density ( \Sigma _ { \textrm { SFR } } ) and star formation efficiency ( SFE ) of GMFs are 0.62 M _ { \sun } Myr ^ { -1 } pc ^ { -2 } and 1 % , similar to the nearby star-forming clouds .
The star formation rate per free-fall time of GMFs is between 0.002 - 0.05 with the median value of 0.02 .
We also find a strong correlation between SFR and dense gas mass that is defined as gas mass above a visual extinction of 7 mag , which suggests that the SFRs of the GMFs scale similarly with dense gas as those of nearby molecular clouds .
We also find a strong correlation between the mean SFR per unit length and dense gas mass per unit length .
The origin of this scaling remains unknown , calling for further studies that can link the structure of GMFs to their SF activity and explore the differences between GMFs and other molecular clouds .

Conclusions :