Employees - Summary of Movements in Liabilities (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	€ 2,569	€ 2,993
Gross service cost	(128)	(186)
Special termination benefits	14	11	€ 15
Past service costs including losses/(gains) on curtailments	3	0
Actuarial gains/(losses) arising from changes in demographic assumptions	98	(24)
Actuarial gains/(losses) arising from changes in financial assumptions	(552)	6,914
Actuarial gain/(loss) arising from experience adjustments	(416)	(760)
Benefit payments	0	0
Other	0	13
Currency retranslation	186	(63)
Net defined benefit liability (asset)	2,401	2,569	2,993
Increase (decrease) resulting from reclassification to defined benefit	0
Present value of defined benefit obligation
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	(16,564)	(23,650)
Gross service cost	(128)	(186)
Special termination benefits	(14)	(11)
Past service costs including losses/(gains) on curtailments	3	0
Settlements	3	1
Interest income	(749)	(452)
Actuarial gains/(losses) arising from changes in demographic assumptions	98	(24)
Actuarial gains/(losses) arising from changes in financial assumptions	(552)	6,914
Actuarial gain/(loss) arising from experience adjustments	(416)	(760)
Benefit payments	1,122	1,184
Other	(371)	15
Currency retranslation	46	405
Net defined benefit liability (asset)	(17,522)	(16,564)	(23,650)
Increase (decrease) resulting from reclassification to defined benefit	368
UK
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	1,866	2,879
Gross service cost	(42)	(86)
Special termination benefits	0	0
Past service costs including losses/(gains) on curtailments	0	0
Actuarial gains/(losses) arising from changes in demographic assumptions	104	1
Actuarial gains/(losses) arising from changes in financial assumptions	(243)	4,196
Actuarial gain/(loss) arising from experience adjustments	(220)	(276)
Benefit payments	0	0
Other	0	0
Currency retranslation	44	(99)
Net defined benefit liability (asset)	1,429	1,866	2,879
UK \| Present value of defined benefit obligation
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	(6,838)	(11,453)
Gross service cost	(42)	(86)
Special termination benefits	0	0
Past service costs including losses/(gains) on curtailments	0	0
Settlements	0	0
Interest income	(335)	(210)
Actuarial gains/(losses) arising from changes in demographic assumptions	104	1
Actuarial gains/(losses) arising from changes in financial assumptions	(243)	4,196
Actuarial gain/(loss) arising from experience adjustments	(220)	(276)
Benefit payments	459	511
Other	0	0
Currency retranslation	(135)	479
Net defined benefit liability (asset)	(7,250)	(6,838)	(11,453)
The Netherlands
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	1,609	1,162
Gross service cost	(5)	(4)
Special termination benefits	0	0
Past service costs including losses/(gains) on curtailments	0	0
Actuarial gains/(losses) arising from changes in demographic assumptions	0	(50)
Actuarial gains/(losses) arising from changes in financial assumptions	(236)	1,527
Actuarial gain/(loss) arising from experience adjustments	(99)	(377)
Benefit payments	0	0
Other	0	(1)
Currency retranslation	0	0
Net defined benefit liability (asset)	1,483	1,609	1,162
The Netherlands \| Present value of defined benefit obligation
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	(3,734)	(4,937)
Gross service cost	(5)	(4)
Special termination benefits	0	0
Past service costs including losses/(gains) on curtailments	0	0
Settlements	0	0
Interest income	(135)	(54)
Actuarial gains/(losses) arising from changes in demographic assumptions	0	(50)
Actuarial gains/(losses) arising from changes in financial assumptions	(236)	1,527
Actuarial gain/(loss) arising from experience adjustments	(99)	(377)
Benefit payments	178	161
Other	0	0
Currency retranslation	0	0
Net defined benefit liability (asset)	(4,031)	(3,734)	(4,937)
Rest of world
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	(906)	(1,048)
Gross service cost	(81)	(96)
Special termination benefits	14	11
Past service costs including losses/(gains) on curtailments	3	0
Actuarial gains/(losses) arising from changes in demographic assumptions	(6)	25
Actuarial gains/(losses) arising from changes in financial assumptions	(73)	1,191
Actuarial gain/(loss) arising from experience adjustments	(97)	(107)
Benefit payments	0	0
Other	0	14
Currency retranslation	142	36
Net defined benefit liability (asset)	(511)	(906)	(1,048)
Rest of world \| Present value of defined benefit obligation
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	(5,992)	(7,260)
Gross service cost	(81)	(96)
Special termination benefits	(14)	(11)
Past service costs including losses/(gains) on curtailments	3	0
Settlements	3	1
Interest income	(279)	(188)
Actuarial gains/(losses) arising from changes in demographic assumptions	(6)	25
Actuarial gains/(losses) arising from changes in financial assumptions	(73)	1,191
Actuarial gain/(loss) arising from experience adjustments	(97)	(107)
Benefit payments	485	512
Other	(371)	15
Currency retranslation	181	(74)
Net defined benefit liability (asset)	€ (6,241)	€ (5,992)	€ (7,260)

The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in demographic assumptions that result in remeasurements of the net defined benefit liability (asset). Demographic assumptions deal with matters such as: (a) mortality; (b) rates of employee turnover, disability and early retirement; (c) the proportion of plan members with dependants who will be eligible for benefits; (d) the proportion of plan members who will select each form of payment option available under the plan terms; and (e) claim rates under medical plans. [Refer: Net defined benefit liability (asset)]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2023-01-01
-Paragraph 141
-Subparagraph c
-Clause ii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_141_c_ii&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_ActuarialGainsLossesArisingFromChangesInDemographicAssumptionsNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in financial assumptions that result in remeasurements of the net defined benefit liability (asset). Financial assumptions deal with items such as: (a) the discount rate; (b) benefit levels, excluding any cost of the benefits to be met by employees, and future salary; (c) in the case of medical benefits, future medical costs, including claim handling costs (ie the costs that will be incurred in processing and resolving claims, including legal and adjuster's fees); and (d) taxes payable by the plan on contributions relating to service before the reporting date or on benefits resulting from that service. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2023-01-01
-Paragraph 141
-Subparagraph c
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_141_c_iii&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_ActuarialGainsLossesArisingFromChangesInFinancialAssumptionsNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from experience adjustments that result in remeasurements of the net defined benefit liability (asset). Experience adjustments deal with the effects of differences between the previous actuarial assumptions and what has actually occurred. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2023-01-01
-Paragraph 141
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_141_c&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_ActuarialGainsLossesArisingFromExperienceAdjustmentsNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from employee service in the current period. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2023-01-01
-Paragraph 141
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_141_a&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_CurrentServiceCostNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

+ References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfDefinedBenefitPlansLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The decrease (increase) in the net defined benefit liability (asset) resulting from settlements. Settlements are transactions that eliminate all further legal or constructive obligations for part or all of the benefits provided under a defined benefit plan, other than a payment of benefits to, or on behalf of, employees that is set out in the terms of the plan and included in the actuarial assumptions. [Refer: Net defined benefit liability (asset); Defined benefit plans [member]; Actuarial assumptions [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2023-01-01
-Paragraph 141
-Subparagraph d
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_141_d&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_GainsLossesArisingFromSettlementsNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from changes in foreign exchange rates. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2023-01-01
-Paragraph 141
-Subparagraph e
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_141_e&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_IncreaseDecreaseThroughChangesInForeignExchangeRatesNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from changes that the entity does not separately disclose in the same statement or note. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2023-01-01
-Paragraph 141
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_141&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_IncreaseDecreaseThroughOtherChangesNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from the passage of time. [Refer: Interest expense; Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2023-01-01
-Paragraph 141
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_141_b&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_InterestExpenseIncomeNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling. [Refer: Defined benefit plans [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2023-01-01
-Paragraph 140
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_140_a&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_LiabilityAssetOfDefinedBenefitPlans
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from past service cost. Past service cost is the change in the present value of the defined benefit obligation for employee service in prior periods, resulting from a plan amendment (the introduction or withdrawal of, or changes to, a defined benefit plan) or a curtailment (a significant reduction by the entity in the number of employees covered by a plan). [Refer: Net defined benefit liability (asset); Defined benefit plans [member]]

+ References

+ Details

Name:	ifrs-full_PastServiceCostNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The decrease (increase) in the net defined benefit liability (asset) resulting from payments from the plan. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2023-01-01
-Paragraph 141
-Subparagraph g
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_141_g&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_PaymentsFromPlanNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of expense in relation to termination benefits. Termination benefits are employee benefits provided in exchange for the termination of an employee's employment as a result of either: (a) an entity's decision to terminate an employee's employment before the normal retirement date; or (b) an employee's decision to accept an offer of benefits in exchange for the termination of employment. [Refer: Employee benefits expense]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2023-01-01
-Paragraph 171
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_171&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_TerminationBenefitsExpense
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Decrease (Increase) In Net Defined Benefit Liability (Asset) Resulting From Reclassification

+ References

No definition available.

+ Details

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

- Details

Name:	ifrs-full_NetDefinedBenefitLiabilityAssetAxis=ifrs-full_PresentValueOfDefinedBenefitObligationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_GeographicalAreasAxis=country_GB
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_GeographicalAreasAxis=country_NL
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_GeographicalAreasAxis=ul_AllOtherCountriesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: