Complex or inaccessible language
Cancellation consequence written in legalese
A fictional service describes the effect of cancellation through a 220-word clause containing undefined terms and cross-references immediately before confirmation.
Individual HTML example · Interface interference
Payment step changes language without warning
A fictional shop presents product and basket information in English but switches mandatory fee and return text to another language on the payment screen.
This is an original fictional comparison. It depicts no real company and is not a legal finding or safe harbour.
Payment step changes language without warning
A fictional shop presents product and basket information in English but switches mandatory fee and return text to another language on the payment screen.
Complete payment. Mandatory charge and return conditions appear only in an unexpected language.. Amount affected: €84: Pay €84. Pay €84. Pay €84 after review
Order summary in English. Price, charge and return conditions remain understandable at payment.. Amount affected: €84: Pay €84 after review. Pay €84 after review. Pay €84. Payable total and selected items, expanded: The summary shows the line items and total before “Pay €84 after review” is activated.
Why the first version can mislead: The presentation changes what the user can notice or predict at the checkout decision. The problematic state shows: “Mandatory charge and return conditions appear only in an unexpected language.” Its influence should be tested by comparing the consequence and usability of “Pay €84” with “Pay €84 after review”. A customer may commit without understanding material terms that appear only at the last step.
What a fairer design does: Keep material information in the user’s selected language and clearly offer any necessary language change before payment.
Show annotated differences (2)
Potentially problematic version
- Pay €84 after reviewIn “Payment step changes language without warning”, this element shows how complex or inaccessible language can shape the decision.
Neutral alternative
- Payable total and selected items, expanded: The summary shows the line items and total before “Pay €84 after review” is activated.In “Payment step changes language without warning”, this element keeps the clearer alternative visible at the same decision point.
Review questions (3)
- Do “Pay €84” and “Pay €84 after review” receive comparable prominence and explain their consequences before activation?
- Compare the basket before and after the action, including total and line items; does the mutation satisfy “Locale mismatch or avoidable complexity is evidenced”?
- What neutral rendering or comprehension result would falsify the classification, particularly in light of “user-selected alternate language”?
Complete pattern context
How this example relates to Complex or inaccessible language
Material guidance is presented in a language or level of complexity that makes informed choice materially harder for the target user. The label describes a recurring design mechanism; whether a particular implementation is harmful or unlawful depends on the complete journey, audience, evidence and rules within scope.
The full guide explains inclusion and exclusion criteria, harms, fair design principles, evidence questions and the relevant EU legal information layers. The example page isolates one scenario so it can be shared and discussed without reproducing the complete library on one page.
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Sources and provenance for this example
Evidence base
Sources
- An Ontology of Dark Patterns KnowledgeGray et al.; ACM CHI 2024 · Secondary · checked 2026-09-14 · DOI 10.1145/3613904.3642436; arXiv:2309.09640
- Unfair Commercial Practices DirectiveEuropean Parliament and Council of the European Union · Primary · checked 2026-08-09 · Directive 2005/29/EC; CELEX 02005L0029-20220528