Amazon's Mechanical Turk, the original AI-labeling marketplace, freezes new sign-ups

Amazon's Mechanical Turk, the 20-year-old crowdsourcing marketplace where humans complete small paid tasks, from survey-taking to AI training-data labeling, will stop accepting new customers on July 30. The freeze is not a sunset: existing requesters and workers keep their accounts, and the platform enters what AWS calls a "Services in Maintenance" posture, with security and availability work continuing but no new features. What the closure does signal is structural. The original human-in-the-loop engine of the AI era is being parked by the same company that spent the past decade building the managed annotation services that grew up around it.

The Register first reported the closure, and AWS confirmed it through updated SageMaker workforce management documentation. The change applies to Mechanical Turk requester accounts across all task types, not only the SageMaker integration surface. A spokesperson told The Register that existing customers are not affected, and AWS has not announced an end-of-life date for those accounts; the door closes on new sign-ups and stays open behind them.

Mechanical Turk launched in November 2005, before Freelancer and Fiverr existed, and was acquired by Amazon in 2007. For most of its life it was the default venue for academic survey research, psychology experiments, and the small, fiddly judgment calls that early machine-learning datasets needed humans to make. After 2018, AWS repositioned the platform as one of several workforce options inside SageMaker Ground Truth, the service that lets AI teams pay humans to draw bounding boxes, label sentiment, or clean up training data. AWS now offers Ground Truth Plus as a higher-touch managed labeling service, Amazon Augmented AI for human review of model outputs, and the option to plug in third-party vendors directly. The work MTurk used to capture has since been disaggregated and rebuilt inside AWS proper.

This is the part the headline framing misses. The story is not "AI killed the human worker." It is that the on-demand human-annotation model MTurk pioneered got absorbed into managed AI infrastructure before it could complete its arc as a standalone marketplace. The training-data supply chain now runs through vendor pipelines and internal tooling rather than a public task feed. AI did not render the crowd obsolete; the platform it lived on got reabsorbed by the rest of the stack.

The people the freeze touches most directly are on two sides of the same ledger. Academic researchers who depended on Mechanical Turk as a quick, cheap subject pool now face a four-week window to migrate studies already in progress to alternatives like Prolific, Cloud Research, or in-house panels. Crowd workers, many in the US and abroad doing this work part-time, are already reporting short-notice account closures on the r/mturk subreddit. Those complaints are anecdotal, and AWS has not confirmed any coordinated account action.

Competitor commentary is worth flagging as labeled opinion rather than neutral analysis. Prolific co-founder Phelim Bradley publicly attributed MTurk's trajectory to "years of degrading data quality and an unhealthy marketplace." Prolific advisor Brad Flora pointed back to Prolific's 2019 origin story as a direct response to MTurk's weaknesses. Neither claim is corroborated by AWS; both are useful as competitor positioning at the moment a competitor's main rival loses its front door.

What remains unresolved is the timing question. AWS has not given a public reason for the freeze. The company could be trimming a service that never fit cleanly inside its enterprise sales motion. It could be clearing space for Ground Truth Plus. It could be doing both. The four weeks between now and July 30 will tell users whether existing accounts quietly keep working or start to degrade, which is the watch item. Either way, the marketplace that helped feed the first generation of AI training sets is closing its front door to the next one.