# Preview defaults for protected preview deployments

> Set custom headers and a concurrency cap once, and every preview environment created for a PR review inherits them.

Source: https://qa.tech/changelog/2026-10-02-preview-defaults-for-preview-environments · Published: 2026-10-02

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Under Settings → Applications & Envs → Preview Environments, the new "Preview defaults" form takes custom headers – for example a Vercel protection bypass header – and a max concurrent tests cap. They are copied onto each new preview environment and refreshed on the next review if you rotate a secret.

The GitHub Action and API pick up the defaults when you don't pass `customHeaders`. Passing it replaces the headers for that preview, and `[]` clears them.

More on this: [PR testing](https://qa.tech/product/pr-testing), [multi-environment testing](https://qa.tech/use-cases/multi-environment-testing), [PR and CI/CD testing](https://qa.tech/use-cases/pr-cicd-testing) and [the Linear + Cursor + Vercel + QA.tech stack](https://qa.tech/blog/ai-builder-stack-linear-cursor-vercel-qa-tech).