A staple defense across judo, jiu-jitsu, and reality-based curricula: the side headlock is common in street violence and predictable in its structural weakness.
Break free of a standing side headlock choke before your air runs out.
The first job is your airway. Bury your chin deep into the crook of their elbow. A tucked chin borrows seconds and buys you the space to work.
Drop your base low and step the near foot out to break their hip line. Their strength was standing above you; the moment you drop, that strength collapses.
As their base breaks, drag their near arm down and across their body. Your head slips free, you emerge behind their shoulder, and you finish with a shove or exit. Do not stand and trade - move to distance.