gabriel-vasile · gabriel-vasile · Jul 21, 2025 · Jul 21, 2025
diff --git a/internal/charset/charset.go b/internal/charset/charset.go
@@ -209,15 +209,8 @@ func fromHTML(s scan.Bytes) string {
 	meta := []byte("<META")
 	lmeta := len(meta)
 	for {
-		if len(s) == 0 {
-			return ""
-		}
-		if bytes.HasPrefix(s, []byte("<!--")) {
-			// Offset by two (<!) because the starting and ending -- can be the same.j
-			s.Advance(2)
-			if i := bytes.Index(s, []byte("-->")); i != -1 {
-				s.Advance(i)
-			}
+		if markup.SkipAComment(&s) {
+			continue
 		}
 		if len(s) <= lmeta {
 			return ""

diff --git a/internal/magic/text.go b/internal/magic/text.go
@@ -29,6 +29,7 @@ var (
 		[]byte("<BODY"),
 		[]byte("<BR"),
 		[]byte("<P"),
+		[]byte("<!--"),
 	)
 	// XML matches an Extensible Markup Language file.
 	XML = markup([]byte("<?XML"))
@@ -236,13 +237,16 @@ func Svg(raw []byte, limit uint32) bool {
 // svgWithoutXMLDeclaration matches a SVG image that does not have an XML header.
 // Example:
 //
+//	<!-- xml comment ignored -->
 //	<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
 //	    <rect fill="#fff" stroke="#000" x="-70" y="-70" width="390" height="390"/>
 //	</svg>
 func svgWithoutXMLDeclaration(s scan.Bytes) bool {
 	for scan.ByteIsWS(s.Peek()) {
 		s.Advance(1)
 	}
+	for mkup.SkipAComment(&s) {
+	}
 	if !bytes.HasPrefix(s, []byte("<svg")) {
 		return false
 	}

diff --git a/internal/markup/markup.go b/internal/markup/markup.go
@@ -3,6 +3,8 @@
 package markup
 
 import (
+	"bytes"
+
 	"github.com/gabriel-vasile/mimetype/internal/scan"
 )
 
@@ -88,3 +90,14 @@ func getAValue(s *scan.Bytes) (_ []byte, hasMore bool) {
 		}
 	}
 }
+
+func SkipAComment(s *scan.Bytes) (skipped bool) {
+	if bytes.HasPrefix(*s, []byte("<!--")) {
+		// Offset by 2 len(<!) because the starting and ending -- can be the same.
+		if i := bytes.Index((*s)[2:], []byte("-->")); i != -1 {
+			s.Advance(i + 2 + 3) // 2 comes from len(<!) and 3 comes from len(-->).
+			return true
+		}
+	}
+	return false
+}
diff --git a/internal/markup/markup_test.go b/internal/markup/markup_test.go
@@ -229,3 +229,33 @@ func TestGetAllAttributes(t *testing.T) {
 		})
 	}
 }
+
+func TestSkipAComment(t *testing.T) {
+	tcases := []struct {
+		in      string
+		out     string
+		skipped bool
+	}{{
+		"", "", false,
+	}, {
+		"abc", "abc", false,
+	}, {
+		"<!--", "<!--", false, // not ending comment
+	}, {
+		"<!-- abc -->", "", true, // regular comment
+	}, {
+		"<!-->", "", true, // the beginning and ending -- are the same chars
+	}}
+	for _, tc := range tcases {
+		t.Run(tc.in, func(t *testing.T) {
+			s := scan.Bytes(tc.in)
+			skipped := SkipAComment(&s)
+			if tc.skipped != skipped {
+				t.Errorf("skipped got: %v, want: %v", skipped, tc.skipped)
+			}
+			if string(s) != tc.out {
+				t.Errorf("got: %v, want: %v", string(s), tc.out)
+			}
+		})
+	}
+}
diff --git a/mimetype_test.go b/mimetype_test.go
@@ -132,6 +132,12 @@ a,"b`,
 		"text/html; charset=iso-8859-1",
 		none,
 	},
+	{
+		"html with comment prefix",
+		`<!-- this comment should not affect --><html><head>`,
+		"text/html; charset=utf-8",
+		none,
+	},
 	{"ico 01", "\x00\x00\x01\x00", "image/x-icon", one},
 	{"ico 02", "\x00\x00\x02\x00", "image/x-icon", none},
 	{"ics", "BEGIN:VCALENDAR\n00", "text/calendar", one},
@@ -246,6 +252,12 @@ a,"b`,
 		"image/svg+xml",
 		all,
 	},
+	{
+		"svg with comment prefix",
+		`<!-- this comment should not affect --><svg xmlns="http://www.w3.org/2000/svg"`,
+		"image/svg+xml",
+		none,
+	},
 
 	{"swf", "CWS", "application/x-shockwave-flash", one},
 	{"tar", fromDisk("tar.tar"), "application/x-tar", all},

diff --git a/supported_mimes.md b/supported_mimes.md
@@ -147,8 +147,8 @@ Extension | MIME type | Aliases
 **.jxr** | image/jxr | image/vnd.ms-photo
 **.parquet** | application/vnd.apache.parquet | application/x-parquet
 **.txt** | text/plain | -
-**.html** | text/html | -
 **.svg** | image/svg+xml | -
+**.html** | text/html | -
 **.xml** | text/xml | application/xml
 **.rss** | application/rss+xml | text/rss
 **.atom** | application/atom+xml | -

diff --git a/tree.go b/tree.go
@@ -81,7 +81,7 @@ var (
 		alias("application/x-ogg")
 	oggAudio = newMIME("audio/ogg", ".oga", magic.OggAudio)
 	oggVideo = newMIME("video/ogg", ".ogv", magic.OggVideo)
-	text     = newMIME("text/plain", ".txt", magic.Text, html, svg, xml, php, js, lua, perl, python, json, ndJSON, rtf, srt, tcl, csv, tsv, vCard, iCalendar, warc, vtt)
+	text     = newMIME("text/plain", ".txt", magic.Text, svg, html, xml, php, js, lua, perl, python, json, ndJSON, rtf, srt, tcl, csv, tsv, vCard, iCalendar, warc, vtt)
 	xml      = newMIME("text/xml", ".xml", magic.XML, rss, atom, x3d, kml, xliff, collada, gml, gpx, tcx, amf, threemf, xfdf, owl2).
 			alias("application/xml")
 	json    = newMIME("application/json", ".json", magic.JSON, geoJSON, har, gltf)