From 8fb278667457c5c56f21b2851e9ab82937b46a75 Mon Sep 17 00:00:00 2001 From: Dino Chiesa Date: Wed, 26 Jul 2023 16:56:23 -0700 Subject: [PATCH] describe Access-Control-Request-Headers as optional part of preflight (#28204) --- files/en-us/glossary/preflight_request/index.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/files/en-us/glossary/preflight_request/index.md b/files/en-us/glossary/preflight_request/index.md index 38758160c6fc4a3..7993cc472c4fa50 100644 --- a/files/en-us/glossary/preflight_request/index.md +++ b/files/en-us/glossary/preflight_request/index.md @@ -8,7 +8,7 @@ page-type: glossary-definition A CORS preflight request is a {{Glossary("CORS")}} request that checks to see if the CORS protocol is understood and a server is aware using specific methods and headers. -It is an {{HTTPMethod("OPTIONS")}} request, using three HTTP request headers: {{HTTPHeader("Access-Control-Request-Method")}}, {{HTTPHeader("Access-Control-Request-Headers")}}, and the {{HTTPHeader("Origin")}} header. +It is an {{HTTPMethod("OPTIONS")}} request, using two or three HTTP request headers: {{HTTPHeader("Access-Control-Request-Method")}}, {{HTTPHeader("Origin")}}, and optionally {{HTTPHeader("Access-Control-Request-Headers")}}. A preflight request is automatically issued by a browser and in normal cases, front-end developers don't need to craft such requests themselves. It appears when request is qualified as ["to be preflighted"](/en-US/docs/Web/HTTP/CORS#preflighted_requests) and omitted for [simple requests](/en-US/docs/Web/HTTP/CORS#simple_requests).