diff --git a/feature/header.go b/feature/header.go
new file mode 100644
index 0000000000000000000000000000000000000000..1fb5a09789f22eb0b6ed2fbd0ae6719ca1011131
--- /dev/null
+++ b/feature/header.go
@@ -0,0 +1,48 @@
+package feature
+
+import (
+	"context"
+	"net/http"
+	"strings"
+)
+
+var featureCtxKey = &contextKey{"feature"}
+
+type contextKey struct {
+	name string
+}
+
+// Creates an HTTP middleware to process Accept-Features headers.
+func Middleware() func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			header := r.Header.Get("Accept-Features")
+			features := strings.Split(header, ",")
+
+			ctx := context.WithValue(r.Context(),
+				featureCtxKey, features)
+			r = r.WithContext(ctx)
+			next.ServeHTTP(w, r)
+		})
+	}
+}
+
+// Returns the list of enabled features on this context.
+func ForContext(ctx context.Context) []string {
+	raw, ok := ctx.Value(featureCtxKey).([]string)
+	if !ok {
+		return []string{}
+	}
+	return raw
+}
+
+// Returns true if the requested feature is enabled via the Accept-Features
+// HTTP header
+func Enabled(ctx context.Context, name string) bool {
+	for _, feat := range ForContext(ctx) {
+		if feat == name {
+			return true
+		}
+	}
+	return false
+}
diff --git a/server/server.go b/server/server.go
index f92d70b92abcfdd820c59977ee06ef5b2c04baa2..18987318ab71e4527c85e0281bfa5f69ac8cd2ac 100644
--- a/server/server.go
+++ b/server/server.go
@@ -39,6 +39,7 @@ 	"git.sr.ht/~sircmpwn/core-go/config"
 	"git.sr.ht/~sircmpwn/core-go/crypto"
 	"git.sr.ht/~sircmpwn/core-go/database"
 	"git.sr.ht/~sircmpwn/core-go/email"
+	"git.sr.ht/~sircmpwn/core-go/feature"
 	"git.sr.ht/~sircmpwn/core-go/redis"
 )
 
@@ -254,7 +255,15 @@ 	})
 	server.router.Use(cors.Handler(cors.Options{
 		AllowedOrigins: []string{"*"},
 		AllowedMethods: []string{"GET", "POST", "OPTIONS"},
-		AllowedHeaders: []string{"User-Agent", "X-Requested-With", "If-Modified-Since", "Cache-Control", "Content-Type", "Range"},
+		AllowedHeaders: []string{
+			"User-Agent",
+			"X-Requested-With",
+			"If-Modified-Since",
+			"Cache-Control",
+			"Content-Type",
+			"Range",
+			"Accept-Features",
+		},
 		ExposedHeaders: []string{"Content-Length", "Content-Range"},
 		MaxAge:         1728000,
 	}))
@@ -264,6 +273,7 @@ 	server.router.Use(database.Middleware(db))
 	server.router.Use(redis.Middleware(rc))
 	server.router.Use(auth.Middleware(server.conf, apiconf))
 	server.router.Use(middleware.RealIP)
+	server.router.Use(feature.Middleware())
 	if debug {
 		server.router.Use(middleware.Logger)
 	}