The present invention relates to a process for the preparation of a hydrogel and to a hydrogel obtainable by said process. The present invention further relates to a process for the preparation of a hydrogel-spacer conjugate, to a hydrogel-spacer conjugate obtainable by said process, to a process for the preparation of a carrier-linked prodrug and to carrier-linked prodrugs obtainable by said process, in particular to carrier-linked prodrugs that provide for a controlled or sustained release of a drug from a carrier. In addition, the invention relates to the use of the hydrogel for the preparation of a carrier-linked prodrug.