Your custom page must be smaller than 1500000 characters.

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Chaika•6/11/25, 3:52 PM

They grab everything, including scripts and any external scripts/fonts/etc which may not be in your dist

When you create or update an asset and provide a URL, Cloudflare collects any images, CSS, and JavaScript code used in the page, minifies the content, and saves it internally.

They used to use https://github.com/cloudflare/collapsify for this but it's archived now, could still use to test though

GitHub

GitHub - cloudflare/collapsify: Collapsify inlines all the resource...

Collapsify inlines all the resources of a page into a single document - cloudflare/collapsify

Chaika•6/11/25, 3:53 PM

I would guess there's some overhead with inlining all the images too, probably just base64ing them

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Chaika•6/11/25, 5:36 PM

hmm, with what error, same size one? Did you try collapsify/can you share the url?

Chaika•6/11/25, 5:49 PM

oh interesting, with the way it was being embedded?

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Chaika•6/11/25, 5:56 PM

IP/Country block is talking about IP Access Rules
If you're doing it in Custom Rules, matching by IP/Country, then that should fall under a waf block

Chaika•6/11/25, 6:05 PM

I believe it's just Pro or higher that lets you set a custom html body per custom rule

Chaika•6/11/25, 6:06 PM

Those have a lot more limited size though iirc

Chaika•6/11/25, 6:08 PM

Response Error Type and Response Error Code are two fields available in Custom Error Rules, you could perhaps do something silly with having the Custom Rule which blocks Countries/IPs return a slightly different status code and then catch it in the Custom Error Rule

.. or you could directly use IP Access Rules potentially, depending on what you're doing

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Chaika•6/12/25, 4:02 PM

You need to pick a custom response type (can be any) and then you can change

Chaika•6/12/25, 4:03 PM

I'll test if this pattern actually works later today, I don't see any reason why it wouldn't but haven't tested fully

Chaika•6/12/25, 4:09 PM

What did you set for the Custom Error rule?

Chaika•6/12/25, 4:11 PM

What happens if you just check for the response status code of 451 and not the error type?

Chaika•6/12/25, 4:13 PM

now that's interesting, hmm using just a simple custom error rule overriding to a static value does work for me, I'll try with a custom asset

Chaika•6/12/25, 4:15 PM

lol yea I think you just stumbled on an unrelated error with using custom asset overrides in error rules, let me see if I can repro fully

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Chaika•6/12/25, 4:27 PM

It looks like this just isn't an intended use case, although it shouldn't error, the docs here say:
https://developers.cloudflare.com/rules/custom-errors/#custom-error-rules

If a security rule like a WAF custom rule or a rate limiting rule triggers a custom block response instead of a default Cloudflare WAF block page, the rule-specific block response will have priority over Error Pages or a matching custom error rule.

Chaika•6/12/25, 4:30 PM

I think the easiest way forward would be to use IP Access Rules to block ASNs/IPs and then just use the error page for IP Blocks
Otherwise, your only option is the Custom Rule Custom Block HTML Response and trimming down your html/making different to fit in its very strict char limit. I don't believe that one tries to bundle the assets at all, so you can use third party links
Kind of meh

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Chaika•6/12/25, 4:30 PM

hmm, wydm? You can't use those to block people, only changing error pages

Chaika•6/12/25, 4:31 PM

Custom Error Pages can only change/do anything for http errors of 400 and above and run after the origin connection (if any)

Chaika•6/12/25, 4:33 PM

oh yea, good thinking, that should work too if your country block list isn't too long and you keep them in sync

Chaika•6/12/25, 4:34 PM

https://developers.cloudflare.com/rules/custom-errors/#how-it-works the hierarchy/order of custom error pages is listed here
Basically going:
Custom Error Page
Custom Error Rule
Custom WAF/Rate Limiting Response within the rule

Chaika•6/12/25, 4:35 PM

It does say this too:

To customize a challenge page or a block page, use an Error Page, since Custom Error Rules will not be applied to security actions originating from Cloudflare products.

but yea it seems to work anyway

Chaika•6/12/25, 4:39 PM

yea I understand your need, and if it works it works. The documentation says it shouldn't work, but without using that your only option would be the custom response within the rule itself which is very limited.
I would just use it this way for now, and you know what you can fall back to if it ever changes.

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Chaika•6/12/25, 9:28 PM

still broken now? If it worked for a bit and stopped, not sure if the big incident that happened was related

Your custom page must be smaller than 1500000 characters.

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