Known issues
Below are some known bugs and issues to be aware of when using Cloudflare Workers.
Route specificity
- When defining route specificity, a trailing
/*
in your pattern may not act as expected.
Consider two different Workers, each deployed to the same zone. Worker A is assigned the example.com/images/*
route and Worker B is given the example.com/images*
route pattern. With these in place, here are how the following URLs will be resolved:
// (A) example.com/images/*
// (B) example.com/images*
"example.com/images"
// -> B
"example.com/images123"
// -> B
"example.com/images/hello"
// -> B
You will notice that all examples trigger Worker B. This includes the final example, which exemplifies the unexpected behavior.
When adding a wildcard on a subdomain, here are how the following URLs will be resolved:
// (A) *.example.com/a
// (B) a.example.com/*
"a.example.com/a"
// -> B
wrangler dev
- When running
wrangler dev --remote
, all outgoing requests are given thecf-workers-preview-token
header, which Cloudflare recognizes as a preview request. This applies to the entire Cloudflare network, so making HTTP requests to other Cloudflare zones is currently discarded for security reasons. To enable a workaround, insert the following code into your Worker script:
const request = new Request(url, incomingRequest);request.headers.delete('cf-workers-preview-token');
return await fetch(request);
Custom ports
For Workers subrequests, when a Worker is deployed, custom ports are ignored and requests are sent to the scheme’s default port, such as 443
for HTTPS. Note that when developing a Worker locally, or from within the Cloudflare dashboard using Quick Edit, custom ports are respected and allowed.
For example:
await fetch('https://example.com:1234/foo')
is the equivalent of:
await fetch('https://example.com/foo')
Fetch to IP addresses
For Workers subrequests, requests can only be made to URLs, not to IP addresses directly. To overcome this limitation add a A or AAAA name record to your zone and then fetch that resource.
For example, in the zone example.com
create a record of type A
with the name server
and value 192.0.2.1
, and then use:
await fetch('http://server.example.com')
Do not use:
await fetch('http://192.0.2.1')