diff --git a/internal/common/common.go b/internal/common/common.go
index 1b008f7..c6e0cb3 100644
--- a/internal/common/common.go
+++ b/internal/common/common.go
@@ -1,20 +1,33 @@
 package common
 
 const (
-	HeaderAcceptLanguage  string = "Accept-Language"
-	HeaderAuthorization   string = "Authorization"
-	HeaderContentLanguage string = "Content-Language"
-	HeaderContentType     string = "Content-Type"
-	HeaderCookie          string = "Cookie"
+	HeaderAccept                   string = "Accept"
+	HeaderAcceptLanguage           string = "Accept-Language"
+	HeaderAuthorization            string = "Authorization"
+	HeaderContentLanguage          string = "Content-Language"
+	HeaderContentType              string = "Content-Type"
+	HeaderCookie                   string = "Cookie"
+	HeaderAccessControlAllowOrigin string = "Access-Control-Allow-Origin"
 )
 
 const (
-	MIMETextHTML             string = "text/html"
-	MIMETextHTMLCharsetUTF8  string = MIMETextHTML + "; " + charsetUTF8
-	MIMETextPlain            string = "text/plain"
-	MIMETextPlainCharsetUTF8 string = MIMETextPlain + "; " + charsetUTF8
+	MIMEApplicationActivityJSON            string = "application/activity+json"
+	MIMEApplicationActivityJSONCharsetUTF8 string = MIMEApplicationActivityJSON + "; " + charsetUTF8
+	MIMEApplicationJRDKJSON                string = "application/jrd+json"
+	MIMEApplicationJRDKJSONCharsetUTF8     string = MIMEApplicationJRDKJSON + "; " + charsetUTF8
+	MIMEApplicationJSON                    string = "application/json"
+	MIMEApplicationJSONCharsetUTF8         string = MIMEApplicationJSON + "; " + charsetUTF8
+	MIMEApplicationLdJSON                  string = "application/ld+json"
+	MIMEApplicationLdJSONProfile           string = MIMEApplicationLdJSON + "; " + profile
+	MIMETextHTML                           string = "text/html"
+	MIMETextHTMLCharsetUTF8                string = MIMETextHTML + "; " + charsetUTF8
+	MIMETextPlain                          string = "text/plain"
+	MIMETextPlainCharsetUTF8               string = MIMETextPlain + "; " + charsetUTF8
 )
 
 const Und string = "und"
 
-const charsetUTF8 string = "charset=UTF-8"
+const (
+	charsetUTF8 string = "charset=UTF-8"
+	profile     string = `profile="https://www.w3.org/ns/activitystreams"`
+)