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+---
+title: The Filehost ISUPPORT token
+layout: spec
+work-in-progress: true
+copyrights:
+  -
+    name: "Val Lorentz"
+    email: "progval+ircv3@progval.net"
+    period: "2022"
+  -
+    name: "Simon Ser"
+    period: "2024"
+---
+
+# filehost
+
+This is a work-in-progress specification.
+
+## Motivation
+
+This specification offers a way for servers to advertise a hosting service for
+users to upload files (such as text or images), so they can post them on IRC.
+
+## Architecture
+
+This specification introduces the `draft/FILEHOST` isupport token.
+
+Its value MUST be a URI and SHOULD use the `https` scheme. Clients MUST ignore
+tokens with an URI scheme they don't support. Clients MUST refuse to use
+unencrypted URI transports (such as plain `http`) if the IRC connection is
+encrypted (e.g. via TLS).
+
+Servers MUST accept OPTIONS requests on the upload URI. Servers MAY return an
+`Accept-Post` header field to indicate the MIME types they accept.
+
+When clients wish to upload a file using the server's recommended service, they
+can send a request to the upload URI. The request method MUST be POST. Clients
+SHOULD authenticate their HTTP request with the same credentials used on the
+IRC connection (e.g. HTTP Basic for SASL PLAIN, HTTP Bearer for SASL
+OAUTHBEARER). Clients SHOULD use the `Content-Type`, `Content-Disposition` and
+`Content-Length` header fields to indicate the MIME type, name and size of the
+file to be uploaded.
+
+On success, servers MUST reply with a `201 Created` status code and with a
+`Location` header field indicating the URI of the uploaded file. Servers MUST
+support HEAD and GET requests on the uploaded file URI.
+
+Clients SHOULD gracefully handle other common HTTP status codes that could
+occur.
+
+## Examples
+
+Example isupport token:
+
+    :irc.example.org 005 seunghye draft/FILEHOST=https://irc.example.org/upload
+
+Example OPTIONS response:
+
+    HTTP/1.1 204 No Content
+    Allow: OPTIONS, POST
+    Accept-Post: image/*, video/*
+
+Example POST request:
+
+    POST /upload HTTP/1.1
+    Host: irc.example.org
+    Content-Type: image/jpeg
+    Content-Disposition: attachment; filename="picture.jpeg"
+    Content-Length: 4242
+    Authorization: Basic c2V1bmdoeWU6bm8=
+
+Example POST response:
+
+    HTTP/1.1 201 Created
+    Location: /upload/hoh5eFThae4e.jpeg