Proxy task

Forward HTTP requests through WebPublish to a remote target URL, with automatic CORS headers.

A proxy task forwards incoming HTTP requests to a remote server and relays the response back to the client. From the perspective of the requesting application, the remote content appears to come from 127.0.0.1:9090, not from the original server.

WebPublish adds CORS headers to every proxied response, making proxy tasks particularly useful for web development workflows where the browser would otherwise block cross-origin requests.

How it works

When a request arrives at http://127.0.0.1:9090/{taskId}/{path}, WebPublish strips the task ID prefix and forwards the request to {target}/{path}, where {target} is the remote URL you configured. The remote response — including status code, headers, and body — is relayed back to the client.

Client → http://127.0.0.1:9090/{taskId}/{path}
       ↓ (forwarded by WebPublish)
       → {target}/{path}
       ↑ (response relayed back)
Client ← response from remote server

URL format

http://127.0.0.1:9090/{taskId}/{path}

For example, if the task ID is tiles and the target is https://tile.openstreetmap.org, then:

http://127.0.0.1:9090/tiles/15/16352/10861.png
  → forwards to →
https://tile.openstreetmap.org/15/16352/10861.png

Creating a proxy task

1. Open the new task dialog

   Click Add (or +) in the toolbar.

2. Select the Proxy type

   In the Type field, choose Proxy.

3. Enter the target URL

   In the Path field, enter the full URL of the remote server you want to proxy to, for example https://api.example.com or http://192.168.1.50:8080.

   The Path field stores the target URL for proxy tasks — not a local file path. Include the scheme (http:// or https://) but do not include a trailing slash.

4. Set the task ID and name

   Enter a short ID for the local URL (for example, remote-api). Requests to http://127.0.0.1:9090/remote-api/anything will be proxied to {target}/anything.

5. Save and start

   Click OK to save the task, then click Start to enable it.

Use cases

Bypass CORS in development

Browsers block requests to a different origin than the page’s own origin. A proxy task moves the request to the same origin as your development server:

// Instead of this (blocked by CORS):
fetch('https://remote-api.example.com/data')

// Do this (routed through WebPublish):
fetch('http://127.0.0.1:9090/remote-api/data')

Access remote tile services locally

Point a mapping client at a local proxy URL to work with remote tile endpoints:

L.tileLayer('http://127.0.0.1:9090/osm/{z}/{x}/{y}.png').addTo(map);
// Proxies to the configured remote tile server

Consolidate multiple upstream services

Create one proxy task per upstream service, each with a different ID. Your client application talks only to 127.0.0.1:9090 and WebPublish routes to the appropriate backend.

CORS headers

WebPublish automatically adds CORS headers to every proxied response. This allows browser applications running on any origin to make requests through the proxy without encountering CORS errors.

If the remote server already sets Access-Control-Allow-Origin headers, WebPublish’s proxy may override them. This is generally desirable in development, but be aware of it when connecting to services that use CORS restrictions for security.

Data usage tracking

The proxy task increments its Data used counter by one for each request forwarded (not by byte count). This provides a request count rather than a byte-accurate usage measurement.

Set a Data limit to cap the number of requests the proxy task will forward before it stops accepting new connections.

The proxy task does not validate or authenticate requests before forwarding them. Do not expose a proxy task on a public network interface if the target URL requires protected access or contains sensitive data.