Braintrust vs Kernel: who uses which
Customers, public proof and the companies that use both.
On usedby, 44 companies use Braintrust and 14 use Kernel. 1 company uses both, including Vercel. Braintrust leads among the DevTools & Infrastructure companies on usedby that use either tool.Latest check Oct 25, 2026: 58 of 58 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 Braintrust, Kernel, or both
Every company with a public proof for at least one of the two tools.
43
listed for Braintrust only
1
company uses both
13
listed for Kernel only
On usedby, 43 companies are listed for Braintrust only, 13 are listed for Kernel only and 1 uses both, out of the 57 companies listed for at least one. An absent listing does not prove non-use.
Where it lands
Recently publicly listed customers
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, Braintrust |
|---|---|
 Vercel | On or before Apr 2025 |
By industry
Which tool the companies on usedby use, by industry. Shares of the companies on usedby that use Braintrust, Kernel or both: a share of the companies on usedby, not of the market.
Listed for Braintrust onlyBothListed for Kernel only
More common with Braintrust
- DevTools & Infrastructure12 of the 13 DevTools & Infrastructure companies on usedby that use either tool use Braintrust, 1 of them alongside Kernel.
- Fintech & Payments5 of the 6 Fintech & Payments companies on usedby that use either tool use Braintrust.
- Artificial Intelligence5 of the 5 Artificial Intelligence companies on usedby that use either tool use Braintrust.
Source: every usedby line, from confirmed proofs to job-post signals (the weakest proof level).
Side by side
Facts from our data and from each vendor's public pages. Each line says where it comes from.
Braintrust
KernelWhat customers report
Results as the vendor or the customer published them, with the source and the date.
Braintrust
100,000s of public eval dashboard views
Browserbase
Vendor case study, braintrust.dev, captured Oct 9, 2026
Continuous signal, 30-min fix cycles
Rex
Vendor case study, braintrust.dev, captured Oct 6, 2026
Kernel
cutting browser cold starts by 333x
Stably
Vendor case study, kernel.sh, published May 26, 2026
Questions about Braintrust and Kernel
Which is used more, Braintrust or Kernel?
Braintrust has more customers on usedby: 44 against 14 for Kernel.
Do companies use both Braintrust and Kernel?
Yes. 1 company uses both on usedby, including Vercel.
Who uses Braintrust?
44 companies on usedby, each with the public page that shows it. See who uses Braintrust.
Who uses Kernel?
14 companies on usedby, each with the public page that shows it. See who uses Kernel.
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.