Operating costs - Narrative (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Analysis of income and expense [abstract]
Exchange gains/(losses)	€ (123)	€ 20	€ (236)

Gain losses on exchange difference amounts on forward contracts and underlying transactions.

No definition available.

Name:	ul_GainLossOnExchangeDifferenceAmountsOnForwardContractsAndUnderlyingTransactions
Namespace Prefix:	ul_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration