Microsoft-backed OpenAI's popular chatbot ChatGPT was back up after an outage affected thousands of users, the company said on Friday.

"Issues with ChatGPT have now been resolved," OpenAI said in a statement on its website.

Access was restored to most users by 4:34 p.m. PT (0034 GMT on Saturday), OpenAI said, adding that a small number of customers faced issues until 5 p.m. (0100 GMT on Saturday).

OpenAI CEO Sam Altman posted on X that ChatGPT had been down for 30 minutes, adding a frown emoji and saying, "We are much, much better at reliability than we used to be, but clearly more work in front of us."

Outage tracking website Downdetector.com said ChatGPT's services were down for about half an hour, affecting over 19,403 users as of 7:13 p.m. ET (0013 GMT on Saturday).

Since the launch of ChatGPT in November 2022, it has attracted 250 million weekly active users. OpenAI's valuation has jumped to $157 billion from $14 billion in 2021 as revenues climbed to $3.6 billion from zero, far exceeding Altman's projections at the time.