Microsoft Copilot vs OpenAI API: who uses which
Customers, public proof and the companies that use both.
On usedby, 4 companies use Microsoft Copilot and 39 use OpenAI API. 1 company uses both, including WPP. OpenAI API leads among the DevTools & Infrastructure companies on usedby that use either tool.Latest check Oct 25, 2026: 42 of 43 public lines checked. Counts include every proof level, job-post signals included. A company on both tools counts at any proof level, and a job post on one side is marked as such.
Who uses Microsoft Copilot, OpenAI API, or both
Every company with a public proof for at least one of the two tools.
3
listed for Microsoft Copilot only
1
company uses both
1 of them is listed through a job post on one side, the weakest proof.
38
listed for OpenAI API only
On usedby, 3 companies are listed for Microsoft Copilot only, 38 are listed for OpenAI API only and 1 uses both, 1 of them through a job post on one side, out of the 42 companies listed for at least one. An absent listing does not prove non-use.
Who uses both
Companies with a public line on both tools, at any proof level: the strongest proofs come first, and a job post is marked.
| Company | First public proof, Microsoft Copilot | First public proof, OpenAI API |
|---|---|---|
 WPPjob posts for both | Job post, Sep 2026 | Job post, Oct 2026 |
Side by side
Facts from our data and from each vendor's public pages. Each line says where it comes from.
Microsoft Copilot
OpenAI APIPricing, security and data residency are not checked yet. usedby adds them from each vendor's public pages, with the date of the check.
Questions about Microsoft Copilot and OpenAI API
Which is used more, Microsoft Copilot or OpenAI API?
OpenAI API has more customers on usedby: 39 against 4 for Microsoft Copilot.
Do companies use both Microsoft Copilot and OpenAI API?
Yes. 1 company uses both on usedby, including WPP.
Who uses Microsoft Copilot?
4 companies on usedby, each with the public page that shows it. See who uses Microsoft Copilot.
Who uses OpenAI API?
39 companies on usedby, each with the public page that shows it. See who uses OpenAI API.
How does usedby count customers?
A company counts when a public page shows it: a vendor's customer page, a case study, a press release or a job post, most saved with a dated capture. Every line is a customer, at one of four proof levels: confirmed, declared by the company itself, observed or signal (a job post, the weakest). A company counts as using both tools when it has a line on each, at any level; the list shows the strongest proofs first and marks job posts.