Most UK visa routes include a restriction which prohibits claiming public funds. This means that visa holders are not able to claim most benefits (including child benefit), tax credits, and housing assistance that are paid by the state.
Please see Home Office guidance for a summary of which benefits and credits are considered to be public funds.
Nationals of some countries are entitled to claim some types of public funds due to exemptions or reciprocal arrangements between their country and the UK. Internal Home Office guidance discusses exemptions, but advice should always be sought from the Staff Immigration team (SIT) before making any applications for public funds to avoid possibly breaching visa conditions.