v3.25.1

Share-based compensation (Tables) | 12 Months Ended
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Dec. 31, 2024
Share-based compensation |
Schedule of share based compensation stock options activity | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | ​ |  | Weighted |  | ​
​ | ​ | ​ | ​ | Weighted | ​ | average | ​ | Aggregate
​ | ​ | ​ | ​ | average | ​ | remaining | ​ | intrinsic
​ | ​ | Number of | ​ | exercise | ​ | contractual life | ​ | value
​ | ​ | options | ​ | price (US$) | ​ | (years) | ​ | (US$)
As of December 31, 2021 |  | 259,315 |  | 2.5500 |  | 5.60 |  | 1,138
Forfeited |  | — |  | ​ |  | ​ |  | ​
Exercised |  | (133,313) |  | 2.5500 |  | ​ |  | ​
As of December 31, 2022 |  | 126,002 |  | 2.5500 |  | 4.60 |  | 176
Forfeited |  | — |  | ​ |  | ​ |  | ​
Exercised |  | (7,000) |  | 2.5500 |  | ​ |  | ​
As of December 31, 2023 |  | 119,002 |  | 2.5500 |  | 3.60 |  | 132
Forfeited |  | — |  | ​ |  | ​ |  | ​
Exercised |  | (37,502) |  | 2.5500 |  | ​ |  | ​
As of December 31, 2024 |  | 81,500 |  | 2.5500 |  | 2.60 |  | 42
Unvested at December 31, 2024 | ​ | — | ​ | ​ | ​ | ​ | ​ | ​
Exercisable as of December 31, 2024 | ​ | 81,500 | ​ | 2.5500 | ​ | 2.60 | ​ | 42
Share based payment award stock options valuation assumptions | ​
​ | ​ | ​ | ​ | ​
​ |  | 2018 |
Weighted average fair value per option granted |  | US$ | 5.2130 | ​
Weighted average exercise price | ​ | US$ | 2.47 | ​
Risk-free interest rate(1) | ​ | ​ | 2.83 | %
Expected term (in year)(2) | ​ | ​ | 10 | ​
Expected volatility(3) | ​ | ​ | 55 | %
Dividend yield(4) | ​ | ​ | — | ​
(1) | The risk-free interest rate of periods within the contractual life of the share option is based on the China Government Bond yield as at the valuation dates.
(2) | The expected term is the contract life of the option.
(3) | Expected volatility is estimated based on the average of historical volatilities of the comparable companies in the same industry as at the valuation dates.
(4) | The Company has no history or expectation of paying dividend on its ordinary shares. The expected dividend yield was estimated based on the Company’s expected dividend policy over the expected term of the option.
Summary of restricted share units activity | ​
​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Weighted
​ | ​ | Number of | ​ | average
​ | ​ | restricted | ​ | grant-date
​ | ​ | share units | ​ | fair value (US$)
Outstanding, December 31, 2021 | ​ | 6,841,198 | ​ | 15.5702
Granted |  | 5,084,817 |  | 3.1233
Forfeited |  | (1,731,659) |  | 13.4427
Vested |  | (2,921,887) |  | 14.4987
Outstanding, December 31, 2022 |  | 7,272,469 |  | 7.8046
Granted |  | 2,787,407 |  | 2.8824
Forfeited |  | (1,365,256) |  | 7.2654
Vested |  | (3,546,222) |  | 8.5540
Outstanding, December 31, 2023 |  | 5,148,398 |  | 4.7664
Granted |  | 2,732,585 |  | 4.1986
Forfeited |  | (459,733) |  | 4.6775
Vested |  | (3,139,694) |  | 4.7799
Outstanding, December 31, 2024 |  | 4,281,556 |  | 4.4037
Expected to vest at December 31, 2024 |  | 4,010,925 |  | 4.3732

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- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d) -SubTopic 10 -Topic 718 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (e) -SubTopic 10 -Topic 718 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 718 -SubTopic 10 -Subparagraph (f)(2) -Name Accounting Standards Codification -Paragraph 2 -Section 50 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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