Accept-Charset HTTP header removed - not sent by any browser for many…

… years and deprecated (#36854)

files/en-us/_redirects.txt

@@ -12285,6 +12285,7 @@
 /en-US/docs/Web/HTTP/Feature_Policy	/en-US/docs/Web/HTTP/Permissions_Policy
 /en-US/docs/Web/HTTP/Gecko_user_agent_string_reference	/en-US/docs/Web/HTTP/Headers/User-Agent/Firefox
 /en-US/docs/Web/HTTP/HTTP_response_codes	/en-US/docs/Web/HTTP/Status
+/en-US/docs/Web/HTTP/Headers/Accept-Charset	/en-US/docs/Web/HTTP/Headers
 /en-US/docs/Web/HTTP/Headers/Cache-Disposition	/en-US/docs/Web/HTTP/Headers/Content-Disposition
 /en-US/docs/Web/HTTP/Headers/Content-Security-Policy/Sources	/en-US/docs/Web/HTTP/Headers/Content-Security-Policy#fetch_directive_syntax
 /en-US/docs/Web/HTTP/Headers/Content-Security-Policy/navigate-to	/en-US/docs/Web/HTTP/Headers/Content-Security-Policy

files/en-us/_wikihistory.json

@@ -98998,17 +98998,6 @@
     "modified": "2020-10-15T22:23:14.705Z",
     "contributors": ["j9t", "Malvoz", "bershanskiy"]
   },
-  "Web/HTTP/Headers/Accept-Charset": {
-    "modified": "2020-10-15T21:48:48.975Z",
-    "contributors": [
-      "mfuji09",
-      "Tigt",
-      "fscholz",
-      "ottaviano",
-      "Minstel",
-      "teoli"
-    ]
-  },
   "Web/HTTP/Headers/Accept-Encoding": {
     "modified": "2020-12-04T01:30:23.076Z",
     "contributors": [

files/en-us/glossary/forbidden_header_name/index.md

@@ -22,7 +22,6 @@ fetch("https://httpbin.org/get", {
 Names starting with `Sec-` are reserved for creating new headers safe from {{glossary("API","APIs")}} that grant developers control over headers, such as {{domxref("Window/fetch", "fetch()")}}.
 Forbidden header names start with `Proxy-` or `Sec-`, or are one of the following names:
 
-- {{HTTPHeader("Accept-Charset")}}
 - {{HTTPHeader("Accept-Encoding")}}
 - {{HTTPHeader("Access-Control-Request-Headers")}}
 - {{HTTPHeader("Access-Control-Request-Method")}}

files/en-us/learn/server-side/first_steps/client-server_overview/index.md

@@ -78,7 +78,6 @@ User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like
 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
 Referer: https://developer.mozilla.org/en-US/
 Accept-Encoding: gzip, deflate, sdch, br
-Accept-Charset: ISO-8859-1,UTF-8;q=0.7,*;q=0.7
 Accept-Language: en-US,en;q=0.8,es;q=0.6
 Cookie: sessionid=6ynxs23n521lu21b1t136rhbv7ezngie; csrftoken=zIPUJsAZv6pcgCBJSCj1zU6pQZbfMUAT; dwf_section_edit=False; dwf_sg_task_completion=False; _gat=1; _ga=GA1.2.1688886003.1471911953; ffo=true
 ```
@@ -98,7 +97,7 @@ For example, you can see here that:
 
 - My browser (`User-Agent`) is Mozilla Firefox (`Mozilla/5.0`).
 - It can accept gzip compressed information (`Accept-Encoding: gzip`).
-- It can accept the specified set of characters (`Accept-Charset: ISO-8859-1,UTF-8;q=0.7,*;q=0.7`) and languages (`Accept-Language: en-US,en;q=0.8,es;q=0.6`).
+- It can accept the specified languages (`Accept-Language: en-US,en;q=0.8,es;q=0.6`).
 - The `Referer` line indicates the address of the web page that contained the link to this resource (i.e. the origin of the request, `https://developer.mozilla.org/en-US/`).
 
 HTTP requests can also have a body, but it is empty in this case.

files/en-us/mozilla/firefox/releases/10/index.md

@@ -106,7 +106,8 @@ Great progress has been made to update IndexedDB to the latest draft specificati
 
 ### Networking
 
-- The HTTP `Accept-Charset` header is no longer sent in HTTP requests. In its absence, servers should respond by sending UTF-8.
+- The HTTP `Accept-Charset` header is no longer sent in HTTP requests.
+  In its absence, servers should respond by sending UTF-8.
 
 ### Developer tools
 

files/en-us/web/api/htmlformelement/acceptcharset/index.md

@@ -8,18 +8,20 @@ browser-compat: api.HTMLFormElement.acceptCharset
 
 {{APIRef("HTML DOM")}}
 
-The **`HTMLFormElement.acceptCharset`** property represents a
-list of the supported [character encodings](/en-US/docs/Glossary/Character_encoding) for the given {{htmlelement("form")}} element. This list can be
-comma-separated or space-separated.
+The **`HTMLFormElement.acceptCharset`** property represents the {{glossary("character encoding")}} for the given {{htmlelement("form")}} element.
+
+The specification allows a single case-insensitive value of `"UTF-8"`, reflecting the ubiquity of this encoding (historically multiple character encodings could be specified as a comma-separated or space-separated list).
+
+This reflects the value of the form's [`accept-charset`](/en-US/docs/Web/HTML/Element/form#accept-charset) HTML attribute.
 
 ## Value
 
-A string.
+A string which may be a case-insensitive match for `UTF-8`.
 
 ## Examples
 
 ```js
-let inputs = document.forms["my-form"].acceptCharset;
+let charSet = document.forms["my-form"].acceptCharset;
 ```
 
 ## Specifications

files/en-us/web/api/htmlformelement/index.md

@@ -30,7 +30,7 @@ _This interface also inherits properties from its parent, {{domxref("HTMLElement
 - {{domxref("HTMLFormElement.encoding")}} or {{domxref("HTMLFormElement.enctype")}}
   - : A string reflecting the value of the form's [`enctype`](/en-US/docs/Web/HTML/Element/form#enctype) HTML attribute, indicating the type of content that is used to transmit the form to the server. Only specified values can be set. The two properties are synonyms.
 - {{domxref("HTMLFormElement.acceptCharset")}}
-  - : A string reflecting the value of the form's [`accept-charset`](/en-US/docs/Web/HTML/Element/form#accept-charset) HTML attribute, representing the character encoding that the server accepts.
+  - : A string reflecting the value of the form's [`accept-charset`](/en-US/docs/Web/HTML/Element/form#accept-charset) HTML attribute.
 - {{domxref("HTMLFormElement.autocomplete")}}
   - : A string reflecting the value of the form's [`autocomplete`](/en-US/docs/Web/HTML/Element/form#autocomplete) HTML attribute, indicating whether the controls in this form can have their values automatically populated by the browser.
 - {{domxref("HTMLFormElement.noValidate")}}

files/en-us/web/html/attributes/index.md

@@ -34,7 +34,7 @@ Elements in HTML have **attributes**; these are additional values that configure
         <code><a href="/en-US/docs/Web/HTML/Element/form#accept-charset">accept-charset</a></code>
       </td>
       <td>{{ HTMLElement("form") }}</td>
-      <td>List of supported charsets.</td>
+      <td>The character set, which if provided must be <code>"UTF-8"</code>.</td>
     </tr>
     <tr>
       <td>

files/en-us/web/html/element/form/index.md

@@ -25,8 +25,8 @@ This element includes the [global attributes](/en-US/docs/Web/HTML/Global_attrib
 
 - `accept-charset`
 
-  - : Space-separated {{Glossary("character encoding", "character encodings")}} the server accepts. The browser uses them in the order in which they are listed. The default value means [the same encoding as the page](/en-US/docs/Web/HTTP/Headers/Content-Encoding).
-    (In previous versions of HTML, character encodings could also be delimited by commas.)
+  - : The {{Glossary("character encoding")}} accepted by the server.
+    The specification allows a single case-insensitive value of `"UTF-8"`, reflecting the ubiquity of this encoding (historically multiple character encodings could be specified as a comma-separated or space-separated list).
 
 - `autocapitalize`
 

files/en-us/web/http/headers/index.md

@@ -84,9 +84,6 @@ For more details, refer to the [Content negotiation article](/en-US/docs/Web/HTT
 
 - {{HTTPHeader("Accept")}}
   - : Informs the server about the {{Glossary("MIME_type", "types")}} of data that can be sent back.
-- {{HTTPHeader("Accept-Charset")}} {{deprecated_inline}}
-  - : Advertises a client's supported {{glossary("character encoding", "character encodings")}}.
-    It is deprecated because {{Glossary("UTF-8")}} has become ubiquitous and use of the header makes client fingerprinting easier.
 - {{HTTPHeader("Accept-Encoding")}}
   - : The encoding algorithm, usually a [compression algorithm](/en-US/docs/Web/HTTP/Compression), that can be used on the resource sent back.
 - {{HTTPHeader("Accept-Language")}}