OpenAI's DevDay put a new number on ChatGPT's reach and turned the subscription into something other apps can draw on, starting with 16 partners.
· 5 min read · L6 Applications and agents · The Pulse, 29 September 2026
In this story: OpenAI
On 29 September OpenAI held DevDay, its yearly developer conference, and published a recap. It says developers can now launch apps directly to ChatGPT's "collective 1.2B weekly users." Reporters from Engadget, writing live from the room, saw a graphic behind Sam Altman showing the same 1.2 billion figure. The Decoder reported the same day that OpenAI also shared more than 35 million weekly users of ChatGPT Work and Codex, and 2.5 million businesses using OpenAI products.
The recap then changes what a ChatGPT plan is for. Subscribers can now "use your allowance across 16 partners including Cognition's Devin, Notion, Vercel, T3, OpenClaw, and Dactyl, and control how much each can use." For businesses, eligible enterprise customers can apply part of their existing OpenAI commitment toward software from 32 partners, among them Figma, Adobe, Salesforce, Harvey and CrowdStrike. OpenAI also announced Ultrafast, a speed setting it says gives "up to 8x faster token generation (300 tokens per second) in Codex and up to 6x in the API," and a Pro 500 plan with 25 times the usage allowance of ChatGPT Plus. Engadget reported the Pro tier at $500 a month.
Cognition, the company behind the coding agent Devin, confirmed the plan-sharing from its own side the same day. "Starting today, you can now sign in to Devin with ChatGPT," it wrote, and usage inside Devin "counts toward the Codex and ChatGPT Work usage already included in your plan." A person can let Devin use all of it or set a lower limit, and once the limit is reached, sessions carry on using Devin's own included usage until the ChatGPT allowance resets. Cognition says it works in Devin Cloud, Devin Desktop and Devin CLI, on its Pro, Max and Teams plans. So a ChatGPT subscription now pays for work done inside another company's product. That is how a subscription starts to act like a platform: other businesses build on the audience instead of billing it separately.
The size of that audience is the other half. A year earlier, at DevDay on 6 October 2025, Altman told reporters: "More than 800 million people use ChatGPT every week." Going from more than 800 million to 1.2 billion is growth of at most 50 percent in just under a year. It is at most, not exactly, because the 2025 figure was a floor.
OpenAI does not say how it counts a weekly user, so a change in definition could move the number without any change in use. The speed claims are OpenAI's own tests on its own systems; an outside benchmark would confirm or cut them. And a partner on a launch list is not the same as a feature people use: the test is how many of the 16 plan-sharing partners, and how many of the 32 marketplace partners, have customers using them by the end of the year.
The recap does not split the 1.2 billion between paying subscribers and people on the free tier. It does not say how usage inside partner apps is priced to the partner, or how much of a person's plan a partner can consume by default. We found no independent estimate of ChatGPT's weekly users to check the figure against. The recap names the Pro 500 plan but not its price; the $500 a month comes from Engadget's report from the room.
If you pay for ChatGPT, some other apps can now run on that same plan. Devin is the first to say so on its own site, and you can cap how much of your allowance each partner uses from your ChatGPT settings. Nothing about the price of your current plan changes because of DevDay.
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