Display omitted •Hydrogen production from photosynthetic microalgae.•Biophotolysis and fermentation techniques narrated.•Genomic and metabolomic approach on hydrogen production discussed.•State of art techniques to enhance the hydrogen in microalgae capsuled. Hydrogen (H2) is one of the renewable and sustainable energy since it reduces greenhouse gas emissions producing water in its purest form. However, the production of H2 from conventional thermochemical technologies needs a switchover to biological processes to avoid replenishment of nonrenewable energy reservoirs. This may include algae which switch over from oxygen to bioH2 production and simultaneously produce various renewable energy products like biomass, carbon storage products, biofuel, lipids and alcohol. On the offset, the selection of algae entrenched on its metabolic and genomic pathways to screen enzymes and genes enhancing the production of bioH2 inside algal cell is crucial. However, they can be an immense reservoir of bioH2 only if its pretreatment process is economized. The current review identifies the metabolic pathway, enzymes and genes involved for bioH2 production. The review also discusses the state of art techniques, advancements, challenges, and techno-economic aspects for sustainable bioH2 production.