Stock-based compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	May 31, 2025	Feb. 28, 2025	Jul. 31, 2021	Dec. 31, 2025	Dec. 31, 2024	May 31, 2023
Share-based compensation
Granted (in shares)				1,454,250
Stock-based compensation expense				$ 4,033	$ 3,874
Intrinsic value of stock options exercised (less than)				$ 700	$ 100
Weighted average grant-date fair value of stock options granted (in dollars per share)				$ 1.86	$ 0.48
Unrecognized compensation expense				$ 1,500
Share-Based Payment Arrangement, Option
Share-based compensation
Weighted average period for unrecognized compensation expense				2 years 4 months 24 days
Restricted Stock Units (RSUs)
Share-based compensation
Stock-based compensation expense				$ 2,300	$ 1,600
Weighted average grant-date fair value per share of units granted (in dollars per share)				$ 3.14	$ 0.94
Total fair value of shares vested				$ 2,500	$ 400
Weighted average period for unrecognized compensation expense				1 year
Unrecognized compensation expense related to units				$ 4,500
Restricted Stock Units (RSUs) \| Minimum
Share-based compensation
Vesting period				1 year
Restricted Stock Units (RSUs) \| Maximum
Share-based compensation
Vesting period				3 years
Class A Common stock
Share-based compensation
Shares available for future issuance (in shares)				28,709,681
2010 Plan
Share-based compensation
Shares authorized (in shares)			0
2021 Incentive Award Plan
Share-based compensation
Shares authorized (in shares)				5,158,947
Plan term			10 years
2021 Incentive Award Plan \| Share-Based Payment Arrangement, Option \| Employees, Officers and Directors
Share-based compensation
Granted (in shares)				1,454,250	952,470
Stock-based compensation expense				$ 1,700	$ 2,300
2021 Incentive Award Plan \| Class A Common stock
Share-based compensation
Shares authorized (in shares)			4,200,000
Percentage of aggregate number of shares outstanding			5.00%
Maximum number of shares issuable upon exercise of stock option (in shares)			33,900,000
2023 Inducement Plan \| Class A Common stock
Share-based compensation
Shares available for future issuance (in shares)				660,000	217,013	330,000
Number of additional shares authorized (in shares)	442,987	476,000
2021 ESPP
Share-based compensation
Plan term			10 years
Stock-based compensation expense				$ 100	$ 100
2021 ESPP \| Options to purchase common stock under ESPP
Share-based compensation
Maximum percentage of payroll deduction			15.00%
Offering period			6 months
Maximum shares available for purchase per employee (in shares)			100,000
Maximum value of shares available for purchase per employee			$ 25
Discount percentage from market price			85.00%
2021 ESPP \| Class A Common stock
Share-based compensation
Shares authorized (in shares)			400,000
Percentage of aggregate number of shares outstanding			1.00%
Maximum number of shares issuable upon exercise of stock option (in shares)			6,300,000
Shares available for future issuance (in shares)				1,170,124
Shares purchased under plan (in shares)				164,108	287,217

RAPID MICRO BIOSYSTEMS, INC. 10-K