Summary of significant accounting policies - Pension Plan (Details)	12 Months Ended
Dec. 31, 2025 plan
Pension Plan
Number of defined benefit post-retirement plans	3
Change in discount rate that would materially affect the projected benefit obligation	1
SEALSQ Corp
Pension Plan
Number of defined benefit post-retirement plans	1
SEALSQ France SAS
Pension Plan
Number of defined benefit post-retirement plans	1
IC' ALPS SAS
Pension Plan
Number of defined benefit post-retirement plans	1

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

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+ Details