From ff6243fc24335ba6becee2999d3f468f0596d7d1 Mon Sep 17 00:00:00 2001
From: Asllan Maciel <asllanmaciel@gmail.com>
Date: Thu, 17 Sep 2026 13:07:53 -0300
Subject: [PATCH] docs: document supported content encodings

---
 README.md | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index e61d4b6..0af0f48 100644
--- a/README.md
+++ b/README.md
@@ -90,7 +90,7 @@ $notifications = [
             'endpoint' => 'https://example.com/other/endpoint/of/another/vendor/abcdef...',
             'publicKey' => '(stringOf88Chars)',
             'authToken' => '(stringOf24Chars)',
-            'contentEncoding' => 'aesgcm', // one of PushManager.supportedContentEncodings
+            'contentEncoding' => 'aesgcm', // encoding supported by both the browser and this library
         ]),
         'payload' => '{"message":"test"}',
     ]
@@ -130,6 +130,21 @@ $report = $webPush->sendOneNotification(
 );
 ```
 
+#### Content encoding negotiation
+
+Browsers can expose supported content encodings through `PushManager.supportedContentEncodings`. The library exposes its supported encodings through the public `ContentEncoding` enum, so applications can negotiate without duplicating a hard-coded list:
+
+```php
+use Minishlink\WebPush\ContentEncoding;
+
+$librarySupportedContentEncodings = array_map(
+    static fn (ContentEncoding $encoding): string => $encoding->value,
+    ContentEncoding::cases(),
+);
+```
+
+Use this list to validate or negotiate the browser-provided encodings before creating the `Subscription`, then pass the selected value as `contentEncoding`. If there is no overlap, treat the subscription as unsupported instead of guessing an encoding.
+
 ### Authentication (VAPID)
 
 Browsers need to verify your identity. A standard called VAPID can authenticate you for all browsers based on [RFC8292](https://www.rfc-editor.org/rfc/rfc8292).