--- description: Test branch and pull request changes in isolated copies of your Worker before production. title: Previews image: https://developers.cloudflare.com/workers/previews/og.png?v=22643d664d2128d6 --- [Skip to content](#main-content) > Documentation Index > Fetch the complete documentation index at: https://developers.cloudflare.com/workers/llms.txt > Use this file to discover all available pages before exploring further. # Previews Last updated Sep 24, 2026|Copy as Markdown| [View as Markdown](https://developers.cloudflare.com/workers/previews/index.md)| [Agent setup](https://developers.cloudflare.com/agent-setup/) **Previews** give each branch an isolated, production-like environment under the same Worker. Each Preview is [configured with its own variables, secrets, and bindings](https://developers.cloudflare.com/workers/previews/configuration/), served on its own [URL](https://developers.cloudflare.com/workers/previews/custom-domains/), and has its own [observability](https://developers.cloudflare.com/workers/previews/test-and-debug/). Worker Previews requires `Wrangler 4.135.0` or later. Update the project dependency because project commands do not use a newer global installation. ![Worker dashboard showing the Preview dropdown and an overview of bindings, metrics, and deployments](https://developers.cloudflare.com/cdn-cgi/image/onerror=redirect,width=2386,height=1304,format=webp/_astro/previews-dash-overview.BL1UHZHT.png) Used [Version URLs](https://developers.cloudflare.com/workers/versions-and-deployments/version-urls/) or [Wrangler environments](https://developers.cloudflare.com/workers/wrangler/environments/) before? Refer to [Compare workflows](https://developers.cloudflare.com/workers/previews/compare-workflows/) to understand how they differ from Previews and our recommended practices for branch testing. ## How it works Running `npx wrangler preview` creates or updates a Preview for your current branch under the same Worker. As you use `npx wrangler deploy` for production, use `npx wrangler preview` to test a branch before merging. | Branch | Command | What happens | | --- | --- | --- | | `main` | `npx wrangler deploy` | Deploys to production with production settings. | | `feature/login` | `npx wrangler preview` | Creates or updates a Preview with its own settings. | ### URLs Each Preview gets two types of URLs. You can serve them on `workers.dev`, a [custom domain](https://developers.cloudflare.com/workers/previews/custom-domains/), or both. - **Preview URL**: always serves the latest deployment. Share this with your team so they always see the most up-to-date version of your branch. - **Deployment URL**: points to one specific deploy and never changes. Use this to reference or compare exact versions, like linking a specific deploy in a PR review. | Host type | Preview URL | Deployment URL | | --- | --- | --- | | `workers.dev` | `-..workers.dev` | `-..workers.dev` | | Custom domain | `.app.example.com` | `-.app.example.com` | To prevent search engines from indexing your Preview, use its `workers.dev` URL, which includes an `X-Robots-Tag: noindex` response header. For custom domain Preview URLs, use [Cloudflare Access](https://developers.cloudflare.com/workers/previews/custom-domains/#protect-preview-content). ### Settings and isolation Previews do not inherit production settings. Define them in the `previews` block of your Wrangler configuration file. When you run `npx wrangler preview` on a branch, Wrangler creates or updates its Preview using that branch's `previews` block. For more information, refer to [Configuration](https://developers.cloudflare.com/workers/previews/configuration/). Since secrets cannot be stored in the configuration file or version control, use commands to apply [secrets](https://developers.cloudflare.com/workers/previews/configuration/#secrets) to all new Previews or to an individual Preview. Cloudflare automatically provisions a new [Durable Object namespace](https://developers.cloudflare.com/workers/previews/resources/#durable-objects) and [container instances](https://developers.cloudflare.com/workers/previews/resources/#containers) for each Preview. KV, D1, R2, and other resources are isolated when you bind the Preview to a separate resource. For the full matrix, refer to [Resources and isolation](https://developers.cloudflare.com/workers/previews/resources/). Workflow bindings use existing Workflows and do not create Preview-specific Workflows. Service bindings from a Preview call the bound Worker's production deployment. Routes and Cron Triggers target production. Queue consumers cannot target a Preview. For details, refer to [Limitations](https://developers.cloudflare.com/workers/previews/resources/#limitations). ### Access control Preview URLs are public by default. Use [Cloudflare Access](https://developers.cloudflare.com/workers/configuration/cloudflare-access/) to require sign-in. You can protect all Previews on an account, one Worker's Previews, or specific hostnames. Details in [Custom domains](https://developers.cloudflare.com/workers/previews/custom-domains/). ### Limits | Limit | Free plan | Paid plans | | --- | --- | --- | | Previews per Worker | 100 | 500 | | Deployments per Preview | 100 | 100 | When a limit is reached, Cloudflare automatically deletes the oldest to make room: - **Preview limit**: the Preview that was deployed to least recently is deleted. - **Deployment limit**: the oldest deployment in that Preview is deleted. You can also delete Previews yourself with `npx wrangler preview delete --name `. For a pull request cleanup example, refer to [Delete closed pull request Previews](https://developers.cloudflare.com/workers/previews/examples/#delete-closed-pull-request-previews). ## Next steps - [Get started](https://developers.cloudflare.com/workers/previews/get-started/) - Set up your first Preview - [Configuration](https://developers.cloudflare.com/workers/previews/configuration/) - Configure variables, secrets, bindings, and Base configuration - [Resources and isolation](https://developers.cloudflare.com/workers/previews/resources/) - Understand which resources are isolated or shared - [Limitations](https://developers.cloudflare.com/workers/previews/resources/#limitations) - Review current support gaps and workarounds Was this helpful? YesNo ## On this page [![](https://developers.cloudflare.com/_astro/logo.te5VL_aD.svg)Docs](https://developers.cloudflare.com/) ```json {"@context":"https://schema.org","@type":"TechArticle","@id":"https://developers.cloudflare.com/workers/previews/#page","headline":"Previews","description":"Test branch and pull request changes in isolated copies of your Worker before production.","url":"https://developers.cloudflare.com/workers/previews/","inLanguage":"en","image":"https://developers.cloudflare.com/workers/previews/og.png?v=22643d664d2128d6","dateModified":"2026-09-24","publisher":{"@type":"Organization","name":"Cloudflare","description":"One platform for your apps, agents, and workforce. 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