Bring your towel and join one of the fastest growing data communities. Welcome to our second-generation open source orchestration platform, a completely rethought approach to dataflow automation.

Prefect Community

<@ULVA73B9P> I have just updated my self-hosted open source Prefect to version 3.7.1 and wanted to try the new UI v2. I could see the original UI v1 page, so the connection was established. When I clicked the banner with suggestion to try new UI, I got just a blank page. The error displayed in Inspect window of my browser was: crypto.randomUUID is not a function
Is it possible that the cause is that I access the page via HTTP instead of HTTPS? Or what can I do to fix the issue and see UI v2?

:white_check_mark: thought for 124.7 seconds

Yes — *HTTP is very likely the cause*.

In Prefect 3.7.1, UI v2 can hit a blank page if the browser console shows:

``` 
crypto.randomUUID is not a function
```

That happens because UI v2 was calling `crypto.randomUUID()` directly, and that API is only available in a *secure context* in browsers — typically:

* `https://...` works
* `<http://localhost>...` usually works
* plain `http://&lt;server-or-ip&gt;` often does *not* work

So if your self-hosted Prefect UI is being accessed over regular HTTP, that can absolutely explain the failure.

*What to do*

*Best fix: upgrade beyond 3.7.1*

This was fixed upstream after 3.7.1 by adding a fallback when `crypto.randomUUID()` is unavailable. If you can, upgrade to a newer 3.7.x release.

Relevant source:
* Fix in `ui-v2/src/api/csrf.ts`: <https://github.com/PrefectHQ/prefect/blob/main/ui-v2/src/api/csrf.ts|csrf.ts>
* Fix commit: <https://github.com/PrefectHQ/prefect/commit/d4554c3022|d4554c3022>

*Alternative fix: serve Prefect over HTTPS*

If you need to stay on 3.7.1, put the UI behind HTTPS via your reverse proxy/load balancer (nginx, Traefik, Caddy, etc.). Make sure the browser actually sees an `https://` URL.

For example, with a reverse proxy you generally want TLS termination and forwarded headers such as:

``` 
X-Forwarded-Proto: https
```

*Quick checks*

1. Open the UI using `https://...` instead of `http://...`
2. If possible, test from `<http://localhost>...`
   * if localhost works but remote HTTP does not, that strongly confirms this is a secure-context issue
3. Check browser dev tools console again after switching to HTTPS

*Bottom line*

* Yes, accessing via HTTP can cause this exact UI v2 error.
* The most reliable solution is to *upgrade to a version newer than 3.7.1*.
* If you stay on 3.7.1, *serve the UI over HTTPS*.

If you want, I can also help you verify:
* whether your current Prefect version already includes the fix, or
* how to configure HTTPS for your specific setup (Docker Compose, nginx, Traefik, Kubernetes, etc.).

in case its helpful: <https://tangled.org/zzstoatzz.io/my-prefect-server/blob/main/deploy/prefect-values.yaml#L18-30>

(ie my config for running my prefect server on a single hetzner node w k3s, using the new UI)

haven't seen this before tho :thinking_face:
&gt;  crypto.randomUUID is not a function
