Need help with custom hostname api | Cloudflare Developers | Page 1

deep gyro Nov 7, 2025, 7:37 AM

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I am working on a website builder saas platform, like wordpress, everything works great, starting from the r2 buckets to the kv namespaces, where users export their project into a subdomain url, but now I am trying to add a custom hostname feature where users will be able to map their own business domain with the exported subdomain url. So I used cloudflare for saas, cloudflare custom hostname api. It looks fine, the custom hostname status and the certifictate status are all active and green after user verified their domain, but when they visit their domain, it says 404 not found, even though every other thing works great, I am really confused of how to pull this off, as I am working with this for the first time, any comments on this would be really helpful, hope you understand what I am trying to say, if you need any more details, please let me know.

crystal sandBOT Nov 7, 2025, 7:37 AM

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Support AI

I understand your concern. Based on the provided documentation, I'd like to offer some insights.

When adding a custom domain, the domain will not verify if Cloudflare cannot validate a request for an SSL certificate on that hostname. In order for the SSL to validate, ensure Cloudflare Access or a Cloudflare Worker is allowing requests to the validation path: http://{domain_name}/.well-known/acme-challenge/*. (Source: https://developers.cloudflare.com/pages/platform/known-issues/)

Additionally, it's essential to review the Hostname prioritization guidelines as wildcard custom hostnames behave differently than an exact hostname match. (Source: https://developers.cloudflare.com/cloudflare-for-platforms/cloudflare-for-saas/start/advanced-settings/apex-proxying/setup/)

To troubleshoot the 404 error, you may want to check the DNS settings and ensure that the custom hostname is correctly configured. You can also try checking the Cloudflare API response for any errors or warnings related to the custom hostname.

If you're still unsure, please provide more details about your setup, such as the API response and the DNS settings, and I'll try to help you further.

Sources

mossy bronze Nov 7, 2025, 11:26 AM

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deep gyro I am working on a website builder saas platform, like wordpress, everything work...

Did you configure the custom hostname on your server as well?

deep gyro Nov 7, 2025, 11:29 AM

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mossy bronze Did you configure the custom hostname on your server as well?

Can you please explain??

mossy bronze Nov 7, 2025, 11:30 AM

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Is your server configured to handle the custom domain or only your own subdomain?

deep gyro Nov 7, 2025, 11:37 AM

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Yeah it is configured, my users can already add the cname records to their own business domain and can also successfully verify those from my saas itself, through the cloudflare custom hostname api, I can also see the status at the selection and tls section in my cloudflare dashboard that the domain aaded for that user is green and active but, when the user visits their domain, it says 404, example: my saas is brivovt.com, so the user exported project url is "anything.brivovt.com" which loads without any problem, then user adds this exported subdomain in his own business(business.com) dns panel like "cname: project.business.com, value: anything.brivovt.com" but when he visits project.business.com, it says 404 not found while anything.brivovt.com works!!

deep gyro Nov 7, 2025, 11:38 AM

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mossy bronze Is your server configured to handle the custom domain or only your own subdomain...

Do you have any tutorial or something where I can get the idea that how is it possible to build this multi tenant feature with cloudflare custom hosname??

mossy bronze Nov 7, 2025, 11:39 AM

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Ok, can you just confirm for me where the users websites are hosted? On your own server running apache/nginx? Or completely on Cloudflare?

deep gyro Nov 7, 2025, 11:39 AM

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Users website are outside cloudflare

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It is in godaddy

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I am using my own domain "thebhargab.com" for testing

mossy bronze Nov 7, 2025, 11:40 AM

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And on GoDaddy, did you add the custom hostname (project.business.com)?

deep gyro Nov 7, 2025, 11:40 AM

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And the backend of my saas is in gcp

deep gyro Nov 7, 2025, 11:40 AM

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mossy bronze And on GoDaddy, did you add the custom hostname (`project.business.com`)?

Yeah I did

mossy bronze Nov 7, 2025, 11:42 AM

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In the Cloudflare Custom Hostnames, do you use the fallback Origin or a Custom Origin for every custom hostname?

deep gyro Nov 7, 2025, 11:42 AM

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Yeah it am using a custom origin hostname as edge.brivovt.com

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Which I even configured in by backend also

mossy bronze Nov 7, 2025, 11:43 AM

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ok, so using a custom origin means that the SNI is changed to the custom origin

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So Cloudflare will send the custom hostname as the HOST header, but the custom origin as the SNI

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Is it the same origin for all sites?

deep gyro Nov 7, 2025, 11:44 AM

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Yeah

mossy bronze Nov 7, 2025, 11:44 AM

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Then I'd consider using the fallback origin rather than custom origins

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On GoDaddy, do you use nginx/apache or something like that?

deep gyro Nov 7, 2025, 11:46 AM

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No I am not using nginx/apache

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I have never done network engineer before

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Can I ask you a favour?

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Is it possible for you to get on a call with me so that can show my screen on a Google meet?

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Or should I drop all my screnshots here?

mossy bronze Nov 7, 2025, 11:47 AM

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no

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You can post screenshots if you'd like

deep gyro Nov 7, 2025, 11:47 AM

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Ok

mossy bronze Nov 7, 2025, 11:47 AM

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Can you share a domain first where you see the 404 right now?

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and also show what settings you made for that domain on Cloudflare?

deep gyro Nov 7, 2025, 11:48 AM

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Give me a few minutes, I am dropping them in

mossy bronze Nov 7, 2025, 11:48 AM

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sure

deep gyro Nov 7, 2025, 11:48 AM

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mossy bronze and also show what settings you made for that domain on Cloudflare?

Yeah sure, I am giving you everything, give me 10 minutes

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here is how I am adding the records from my saas to my domain "thebhargab.com" at godaddy

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here is how I have added these records in godaddy

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here is my ssl status at cloudflare dashboard

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here is my entire dns table of my saas at cloudflare

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when I visit book.brivovt.com, it works and I can see the project, but when I visit book.thebhargab.com, it says 404

mossy bronze Nov 7, 2025, 12:02 PM

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Ok, let me clarify a few things

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you have a website builder on GCP

deep gyro Nov 7, 2025, 12:02 PM

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Yeah

mossy bronze Nov 7, 2025, 12:02 PM

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when the website is done, you deploy it on godaddy

deep gyro Nov 7, 2025, 12:03 PM

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No no

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Go daddy has the domain only

mossy bronze Nov 7, 2025, 12:03 PM

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ahh ok, i misunderstood that part

deep gyro Nov 7, 2025, 12:04 PM

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It's the website builder which is on gcp and the dns of that website builder is on cloudflare. All the exported subdomain url that gets creates appears there only, just for testing, I bought a domain at godaddy to see if it works....

mossy bronze Nov 7, 2025, 12:06 PM

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ok, so on GCP, what settings do you make for a) your own subdomain and b) the custom hostname

deep gyro Nov 7, 2025, 12:08 PM

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deep gyro here is my entire dns table of my saas at cloudflare

I hosted my backend as a webservice on gcp, thats it, from there I got an url, and as you can see in my dns table screenshot, I have mapped those webserive url, in origin and edge cnames

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The subdomains gets created on cloudflare itself, via kv namespace

mossy bronze Nov 7, 2025, 12:09 PM

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How does your service decide which website to serve for which url?

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say I have book.brivovt.com and table.brivovt.com

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Where do you make the decision which website to serve?

deep gyro Nov 7, 2025, 12:13 PM

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After user is done making his website, it gets saved as a index.html file in cloudflare r2 bucket. Then I use worker and kv namespace and set that subdomain -key (book.brivovt.com) to r2publicURL(of that website) -variable.

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you can also visit "book.brivovt.com" from "https://exports.brivo.beakball.com/hosted-tours/hello/462008a5-43cb-4407-9f82-cfcc6b121d80/index.html"

deep gyro Nov 7, 2025, 12:14 PM

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deep gyro you can also visit "book.brivovt.com" from "https://exports.brivo.beakball.com/h...

Both are same thing

mossy bronze Nov 7, 2025, 12:14 PM

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and have you also added the custom hostname to that configuration?

deep gyro Nov 7, 2025, 12:17 PM

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Yeah I also have it in the same kv namespace where it stores the kv pairs as (key: book.thebhargab.com, value:ther2publicurl of the website)

mossy bronze Nov 7, 2025, 12:18 PM

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Ok, so it looks to me like the Worker isn't called for the custom hostname and traffic is sent to GCP

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Did you add the Worker via Workers Routes?

deep gyro Nov 7, 2025, 12:19 PM

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deep gyro Yeah I also have it in the same kv namespace where it stores the kv pairs as (ke...

In summary: the kvnamespace has two things ( key: book.brivovt.com, value: r2publicurl) and (key:book.thebhargab.com, value:that same r2public url)

deep gyro Nov 7, 2025, 12:19 PM

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mossy bronze Did you add the Worker via Workers Routes?

Yeah I did

mossy bronze Nov 7, 2025, 12:19 PM

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what is the route?

deep gyro Nov 7, 2025, 12:20 PM

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tour-router.bhargabdutta.workers.dev

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you can see that in the dns table screenshot too

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here is the worker screenshot

mossy bronze Nov 7, 2025, 12:22 PM

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yeah, ok

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the worker route is *.brivovt.com

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so it doesn't work on book.whatever

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you need a */* route

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and then you need to make exceptions for your own domain that's not supposed to go to the worker

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in the dashboard, go to your domain and select workers routes

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Then you create exceptions for urls that are not supposed to go to the worker:

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And then you create a route for everything else to go to the worker

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Or alternatively, you can create a new route for every custom hostname that you add with the specific domain

deep gyro Nov 7, 2025, 12:26 PM

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Alright can you clarify? What do you mean by "it doesn't work for book.whatever" because book.brivovt.com(subdomain of brivovt.com) works but the book.thebhargab.com(custom hostname of another domain) doent work

mossy bronze Nov 7, 2025, 12:26 PM

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You have a route for *.brivovt.com/*

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But I make a request for book.thebhargab.com

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Which doesn't match the Route, so the Worker is not invoked

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The route works on the url the client is using, not on the origin you have specified

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So option a) add a route for book.thebhargab.com

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I would recommend you do that to see if it works

deep gyro Nov 7, 2025, 12:29 PM

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Ok 1 min, I am doing what you said

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is this what I should do??

mossy bronze Nov 7, 2025, 12:35 PM

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yeah, for example

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Long term, you want to use a */* route so you don't have to add a new route for every custom hostname

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But for trying, this should work

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And it looks like it does work now

deep gyro Nov 7, 2025, 12:37 PM

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ok now this is what I have now

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Yeah yeah

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Thank you soooo much, let me see and test with / with multiple domains of other people

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I'll me right back within a few hours

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Thank you so much @mossy bronze

mossy bronze Nov 7, 2025, 12:42 PM

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Good luck 😉

deep gyro Nov 7, 2025, 12:51 PM

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I got into a problem, when I add / route, my saas itslef stops working, as it is on brivovt.com

mossy bronze Nov 7, 2025, 12:52 PM

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You need to make Worker=None Routes for the things that aren't supposed to go to the worker

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It's usually easier that way than adding a new route for every new custom hostname

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deep gyro Nov 7, 2025, 1:35 PM

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Alright I restricted all the domains that I don't want in my worker

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It's working

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I even tested adding records to other domains

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These are working too

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Thanks a lol @mossy bronze

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Just one last thing I want to ask

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How to learn these things??

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I am just a frontend dev, I started learning backend dev and I have no idea how I got myself into this mess

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Please suggest me any learning materials, book name? Courses? Anything

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I am desperate to learn

mossy bronze Nov 7, 2025, 1:38 PM

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For product specific knowldge like this, you just learn it by spending a lot of time trying things like this.

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Cloudflare has excellent documentation for most things, so it's always worth looking at it:

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https://developers.cloudflare.com/cloudflare-for-platforms/cloudflare-for-saas/start/advanced-settings/worker-as-origin/

Cloudflare Docs

Workers as your fallback origin

Learn how to use a Worker as the fallback origin for your SaaS zone.

deep gyro Nov 7, 2025, 1:39 PM

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Ok

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Thanks

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😊

mossy bronze Nov 7, 2025, 1:41 PM

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There's also probably lots of others people that had the same question you have

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So looking at Cloudflare Community often has the answers

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A lot easier to search there than on Discord

#Need help with custom hostname api