He added he had “nothing else to prove” in the caption, external to his video on social media.
“I spent my whole life chasing something,” said Crawford. “Not belts, not money, not headlines, but that feeling, the one you get when the world doubts you but you keep showing up and you keep proving everyone wrong.
“This sport gave me everything, I fought for my family, I fought for my city, I fought for the kid I used to be, the one that had nothing but a dream and a pair of gloves, and I did it all my way.
“I gave this sport every breath I have, every spar, every triumph, every ounce of my heart. I’ve made peace with what’s next. Now, it’s time. Thank you.”
Omaha-born Crawford had 31 knockouts in his 42 fights, which included WBO welterweight title wins over Britons Amir Khan and Kell Brook.