ChatGPT, Sora, and OpenAI’s developer-facing API experienced a major outage on Thursday that lasted for more than four hours. OpenAI reported that the problem started at 11 a.m. PT but services are slowly coming back online as of 3:16 p.m. PT. Users who frequent ChatGPT may remember that the service also went down earlier this month.

TechCrunch encountered error messages when trying to access ChatGPT and Sora on Thursday afternoon.

OpenAI stated on their status page that the outage was caused by one of their upstream providers, although no further details were provided. By 2:05 p.m. PT, OpenAI mentioned that ChatGPT was partially recovered but users might still face issues loading their chat history. Sora became operational again at 3:16 p.m. PT, with the company actively working on a full fix for ChatGPT and its API.

This marks the second time this December that OpenAI’s services have experienced downtime. A couple of weeks ago, the outage was attributed to a malfunctioning telemetry service and lasted for about 6 hours, a longer disruption than usual as outages usually last only an hour or two.

Popular services utilizing OpenAI’s API, such as Perplexity and Siri’s Apple Intelligence integration, seemed unaffected by the outage based on the respective companies’ status pages and TechCrunch’s testing.