On her Instagram account, Chow posted a plain, black image with a message saying she had grown physically weak during her time behind bars and she needed to recuperate.
She thanked friends who came out in the rain to greet her on her release from Tai Lam Correctional Institution in Tuen Mun on Saturday morning.
“The painful six months and twenty days are finally over,” she wrote.
“The next step is to take some good rest and take care of my body, because my body has become too slim and weak during this period (wry smile).”
By Saturday night, the post had received more than 100,000 “likes” on the website.
Chow was sentenced to 10 months in prison in December after pleading guilty to participating in and inciting an unauthorised assembly outside police headquarters in June 2019. She was released early on grounds of good behaviour
Fellow activists Ivan Lam and Joshua Wong were jailed for seven months and thirteen and a half months over the same case.
Separately, Chow was arrested last year on suspicion of colluding with foreign forces under the national security law, but she has not been charged.