diff --git a/modules/git/blob.go b/modules/git/blob.go
index 14ca2b1445..4eef5f0e2a 100644
--- a/modules/git/blob.go
+++ b/modules/git/blob.go
@@ -220,7 +220,7 @@ func (b *Blob) GuessContentType() (typesniffer.SniffedType, error) {
 	}
 	defer r.Close()
 
-	return typesniffer.DetectContentTypeFromReader(r)
+	return typesniffer.DetectContentTypeFromReader(r, b.Name())
 }
 
 // GetBlob finds the blob object in the repository.
diff --git a/modules/httplib/serve.go b/modules/httplib/serve.go
index c5f0658d4e..d385ac21c9 100644
--- a/modules/httplib/serve.go
+++ b/modules/httplib/serve.go
@@ -99,7 +99,7 @@ func setServeHeadersByFile(r *http.Request, w http.ResponseWriter, filePath stri
 		Filename: path.Base(filePath),
 	}
 
-	sniffedType := typesniffer.DetectContentType(mineBuf)
+	sniffedType := typesniffer.DetectContentType(mineBuf, opts.Filename)
 
 	// the "render" parameter came from year 2016: 638dd24c, it doesn't have clear meaning, so I think it could be removed later
 	isPlain := sniffedType.IsText() || r.FormValue("render") != ""
diff --git a/modules/indexer/code/bleve/bleve.go b/modules/indexer/code/bleve/bleve.go
index c53b7a2e6d..4c8b5f2a86 100644
--- a/modules/indexer/code/bleve/bleve.go
+++ b/modules/indexer/code/bleve/bleve.go
@@ -177,7 +177,7 @@ func (b *Indexer) addUpdate(ctx context.Context, batchWriter git.WriteCloserErro
 	fileContents, err := io.ReadAll(io.LimitReader(batchReader, size))
 	if err != nil {
 		return err
-	} else if !typesniffer.DetectContentType(fileContents).IsText() {
+	} else if !typesniffer.DetectContentType(fileContents, update.Filename).IsText() {
 		// FIXME: UTF-16 files will probably fail here
 		// Even if the file is not recognized as a "text file", we could still put its name into the indexers to make the filename become searchable, while leave the content to empty.
 		fileContents = nil
diff --git a/modules/indexer/code/elasticsearch/elasticsearch.go b/modules/indexer/code/elasticsearch/elasticsearch.go
index 3903d77fe0..9b11f56fb7 100644
--- a/modules/indexer/code/elasticsearch/elasticsearch.go
+++ b/modules/indexer/code/elasticsearch/elasticsearch.go
@@ -144,7 +144,7 @@ func (b *Indexer) addUpdate(ctx context.Context, batchWriter git.WriteCloserErro
 	fileContents, err := io.ReadAll(io.LimitReader(batchReader, size))
 	if err != nil {
 		return nil, err
-	} else if !typesniffer.DetectContentType(fileContents).IsText() {
+	} else if !typesniffer.DetectContentType(fileContents, update.Filename).IsText() {
 		// FIXME: UTF-16 files will probably fail here
 		return nil, nil
 	}
diff --git a/modules/typesniffer/typesniffer.go b/modules/typesniffer/typesniffer.go
index 262feb2b05..8cb1513a88 100644
--- a/modules/typesniffer/typesniffer.go
+++ b/modules/typesniffer/typesniffer.go
@@ -124,7 +124,7 @@ func (ct SniffedType) GetMimeType() string {
 }
 
 // DetectContentType extends http.DetectContentType with more content types. Defaults to text/unknown if input is empty.
-func DetectContentType(data []byte) SniffedType {
+func DetectContentType(data []byte, filename string) SniffedType {
 	if len(data) == 0 {
 		return SniffedType{"text/unknown"}
 	}
@@ -176,6 +176,13 @@ func DetectContentType(data []byte) SniffedType {
 		}
 	}
 
+	if ct == "application/octet-stream" &&
+		filename != "" &&
+		!strings.HasSuffix(strings.ToUpper(filename), ".LCOM") &&
+		bytes.Contains(data, []byte("(DEFINE-FILE-INFO ")) {
+		ct = "text/vnd.interlisp"
+	}
+
 	// GLTF is unsupported by http.DetectContentType
 	// hexdump -n 4 -C glTF.glb
 	if bytes.HasPrefix(data, []byte("glTF")) {
@@ -186,7 +193,7 @@ func DetectContentType(data []byte) SniffedType {
 }
 
 // DetectContentTypeFromReader guesses the content type contained in the reader.
-func DetectContentTypeFromReader(r io.Reader) (SniffedType, error) {
+func DetectContentTypeFromReader(r io.Reader, filename string) (SniffedType, error) {
 	buf := make([]byte, sniffLen)
 	n, err := util.ReadAtMost(r, buf)
 	if err != nil {
@@ -194,5 +201,5 @@ func DetectContentTypeFromReader(r io.Reader) (SniffedType, error) {
 	}
 	buf = buf[:n]
 
-	return DetectContentType(buf), nil
+	return DetectContentType(buf, filename), nil
 }
diff --git a/modules/typesniffer/typesniffer_test.go b/modules/typesniffer/typesniffer_test.go
index 176d3658bb..d2b7ed4f21 100644
--- a/modules/typesniffer/typesniffer_test.go
+++ b/modules/typesniffer/typesniffer_test.go
@@ -16,63 +16,63 @@ import (
 
 func TestDetectContentTypeLongerThanSniffLen(t *testing.T) {
 	// Pre-condition: Shorter than sniffLen detects SVG.
-	assert.Equal(t, "image/svg+xml", DetectContentType([]byte(`<!-- Comment --><svg></svg>`)).contentType)
+	assert.Equal(t, "image/svg+xml", DetectContentType([]byte(`<!-- Comment --><svg></svg>`), "").contentType)
 	// Longer than sniffLen detects something else.
-	assert.NotEqual(t, "image/svg+xml", DetectContentType([]byte(`<!-- `+strings.Repeat("x", sniffLen)+` --><svg></svg>`)).contentType)
+	assert.NotEqual(t, "image/svg+xml", DetectContentType([]byte(`<!-- `+strings.Repeat("x", sniffLen)+` --><svg></svg>`), "").contentType)
 }
 
 func TestIsTextFile(t *testing.T) {
-	assert.True(t, DetectContentType([]byte{}).IsText())
-	assert.True(t, DetectContentType([]byte("lorem ipsum")).IsText())
+	assert.True(t, DetectContentType([]byte{}, "").IsText())
+	assert.True(t, DetectContentType([]byte("lorem ipsum"), "").IsText())
 }
 
 func TestIsSvgImage(t *testing.T) {
-	assert.True(t, DetectContentType([]byte("<svg></svg>")).IsSvgImage())
-	assert.True(t, DetectContentType([]byte("    <svg></svg>")).IsSvgImage())
-	assert.True(t, DetectContentType([]byte(`<svg width="100"></svg>`)).IsSvgImage())
-	assert.True(t, DetectContentType([]byte(`<?xml version="1.0" encoding="UTF-8"?><svg></svg>`)).IsSvgImage())
+	assert.True(t, DetectContentType([]byte("<svg></svg>"), "").IsSvgImage())
+	assert.True(t, DetectContentType([]byte("    <svg></svg>"), "").IsSvgImage())
+	assert.True(t, DetectContentType([]byte(`<svg width="100"></svg>`), "").IsSvgImage())
+	assert.True(t, DetectContentType([]byte(`<?xml version="1.0" encoding="UTF-8"?><svg></svg>`), "").IsSvgImage())
 	assert.True(t, DetectContentType([]byte(`<!-- Comment -->
-	<svg></svg>`)).IsSvgImage())
+	<svg></svg>`), "").IsSvgImage())
 	assert.True(t, DetectContentType([]byte(`<!-- Multiple -->
 	<!-- Comments -->
-	<svg></svg>`)).IsSvgImage())
+	<svg></svg>`), "").IsSvgImage())
 	assert.True(t, DetectContentType([]byte(`<!-- Multiline
 	Comment -->
-	<svg></svg>`)).IsSvgImage())
+	<svg></svg>`), "").IsSvgImage())
 	assert.True(t, DetectContentType([]byte(`<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1 Basic//EN"
 	"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11-basic.dtd">
-	<svg></svg>`)).IsSvgImage())
+	<svg></svg>`), "").IsSvgImage())
 	assert.True(t, DetectContentType([]byte(`<?xml version="1.0" encoding="UTF-8"?>
 	<!-- Comment -->
-	<svg></svg>`)).IsSvgImage())
+	<svg></svg>`), "").IsSvgImage())
 	assert.True(t, DetectContentType([]byte(`<?xml version="1.0" encoding="UTF-8"?>
 	<!-- Multiple -->
 	<!-- Comments -->
-	<svg></svg>`)).IsSvgImage())
+	<svg></svg>`), "").IsSvgImage())
 	assert.True(t, DetectContentType([]byte(`<?xml version="1.0" encoding="UTF-8"?>
 	<!-- Multiline
 	Comment -->
-	<svg></svg>`)).IsSvgImage())
+	<svg></svg>`), "").IsSvgImage())
 	assert.True(t, DetectContentType([]byte(`<?xml version="1.0" encoding="UTF-8"?>
 	<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
 	<!-- Multiline
 	Comment -->
-	<svg></svg>`)).IsSvgImage())
+	<svg></svg>`), "").IsSvgImage())
 
 	// the DetectContentType should work for incomplete data, because only beginning bytes are used for detection
-	assert.True(t, DetectContentType([]byte(`<svg>....`)).IsSvgImage())
+	assert.True(t, DetectContentType([]byte(`<svg>....`), "").IsSvgImage())
 
-	assert.False(t, DetectContentType([]byte{}).IsSvgImage())
-	assert.False(t, DetectContentType([]byte("svg")).IsSvgImage())
-	assert.False(t, DetectContentType([]byte("<svgfoo></svgfoo>")).IsSvgImage())
-	assert.False(t, DetectContentType([]byte("text<svg></svg>")).IsSvgImage())
-	assert.False(t, DetectContentType([]byte("<html><body><svg></svg></body></html>")).IsSvgImage())
-	assert.False(t, DetectContentType([]byte(`<script>"<svg></svg>"</script>`)).IsSvgImage())
+	assert.False(t, DetectContentType([]byte{}, "").IsSvgImage())
+	assert.False(t, DetectContentType([]byte("svg"), "").IsSvgImage())
+	assert.False(t, DetectContentType([]byte("<svgfoo></svgfoo>"), "").IsSvgImage())
+	assert.False(t, DetectContentType([]byte("text<svg></svg>"), "").IsSvgImage())
+	assert.False(t, DetectContentType([]byte("<html><body><svg></svg></body></html>"), "").IsSvgImage())
+	assert.False(t, DetectContentType([]byte(`<script>"<svg></svg>"</script>`), "").IsSvgImage())
 	assert.False(t, DetectContentType([]byte(`<!-- <svg></svg> inside comment -->
-	<foo></foo>`)).IsSvgImage())
+	<foo></foo>`), "").IsSvgImage())
 	assert.False(t, DetectContentType([]byte(`<?xml version="1.0" encoding="UTF-8"?>
 	<!-- <svg></svg> inside comment -->
-	<foo></foo>`)).IsSvgImage())
+	<foo></foo>`), "").IsSvgImage())
 
 	assert.False(t, DetectContentType([]byte(`
 <!-- comment1 -->
@@ -80,7 +80,7 @@ func TestIsSvgImage(t *testing.T) {
 	<!-- comment2 -->
 	<svg></svg>
 </div>
-`)).IsSvgImage())
+`), "").IsSvgImage())
 
 	assert.False(t, DetectContentType([]byte(`
 <!-- comment1
@@ -90,56 +90,56 @@ func TestIsSvgImage(t *testing.T) {
 -->
 	<svg></svg>
 </div>
-`)).IsSvgImage())
-	assert.False(t, DetectContentType([]byte(`<html><body><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><svg></svg></body></html>`)).IsSvgImage())
-	assert.False(t, DetectContentType([]byte(`<html><body><?xml version="1.0" encoding="UTF-8"?><svg></svg></body></html>`)).IsSvgImage())
+`), "").IsSvgImage())
+	assert.False(t, DetectContentType([]byte(`<html><body><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><svg></svg></body></html>`), "").IsSvgImage())
+	assert.False(t, DetectContentType([]byte(`<html><body><?xml version="1.0" encoding="UTF-8"?><svg></svg></body></html>`), "").IsSvgImage())
 }
 
 func TestIsPDF(t *testing.T) {
 	pdf, _ := base64.StdEncoding.DecodeString("JVBERi0xLjYKJcOkw7zDtsOfCjIgMCBvYmoKPDwvTGVuZ3RoIDMgMCBSL0ZpbHRlci9GbGF0ZURlY29kZT4+CnN0cmVhbQp4nF3NPwsCMQwF8D2f4s2CNYk1baF0EHRwOwg4iJt/NsFb/PpevUE4Mjwe")
-	assert.True(t, DetectContentType(pdf).IsPDF())
-	assert.False(t, DetectContentType([]byte("plain text")).IsPDF())
+	assert.True(t, DetectContentType(pdf, "").IsPDF())
+	assert.False(t, DetectContentType([]byte("plain text"), "").IsPDF())
 }
 
 func TestIsVideo(t *testing.T) {
 	mp4, _ := base64.StdEncoding.DecodeString("AAAAGGZ0eXBtcDQyAAAAAGlzb21tcDQyAAEI721vb3YAAABsbXZoZAAAAADaBlwX2gZcFwAAA+gA")
-	assert.True(t, DetectContentType(mp4).IsVideo())
-	assert.False(t, DetectContentType([]byte("plain text")).IsVideo())
+	assert.True(t, DetectContentType(mp4, "").IsVideo())
+	assert.False(t, DetectContentType([]byte("plain text"), "").IsVideo())
 }
 
 func TestIsAudio(t *testing.T) {
 	mp3, _ := base64.StdEncoding.DecodeString("SUQzBAAAAAABAFRYWFgAAAASAAADbWFqb3JfYnJhbmQAbXA0MgBUWFhYAAAAEQAAA21pbm9yX3Zl")
-	assert.True(t, DetectContentType(mp3).IsAudio())
-	assert.False(t, DetectContentType([]byte("plain text")).IsAudio())
+	assert.True(t, DetectContentType(mp3, "").IsAudio())
+	assert.False(t, DetectContentType([]byte("plain text"), "").IsAudio())
 
-	assert.True(t, DetectContentType([]byte("ID3Toy\000")).IsAudio())
-	assert.True(t, DetectContentType([]byte("ID3Toy\n====\t* hi 🌞, ...")).IsText())          // test ID3 tag for plain text
-	assert.True(t, DetectContentType([]byte("ID3Toy\n====\t* hi 🌞, ..."+"🌛"[0:2])).IsText()) // test ID3 tag with incomplete UTF8 char
+	assert.True(t, DetectContentType([]byte("ID3Toy\000"), "").IsAudio())
+	assert.True(t, DetectContentType([]byte("ID3Toy\n====\t* hi 🌞, ..."), "").IsText())          // test ID3 tag for plain text
+	assert.True(t, DetectContentType([]byte("ID3Toy\n====\t* hi 🌞, ..."+"🌛"[0:2]), "").IsText()) // test ID3 tag with incomplete UTF8 char
 }
 
 func TestIsGLB(t *testing.T) {
 	glb, _ := hex.DecodeString("676c5446")
-	assert.True(t, DetectContentType(glb).IsGLB())
-	assert.True(t, DetectContentType(glb).Is3DModel())
-	assert.False(t, DetectContentType([]byte("plain text")).IsGLB())
-	assert.False(t, DetectContentType([]byte("plain text")).Is3DModel())
+	assert.True(t, DetectContentType(glb, "").IsGLB())
+	assert.True(t, DetectContentType(glb, "").Is3DModel())
+	assert.False(t, DetectContentType([]byte("plain text"), "").IsGLB())
+	assert.False(t, DetectContentType([]byte("plain text"), "").Is3DModel())
 }
 
 func TestDetectContentTypeFromReader(t *testing.T) {
 	mp3, _ := base64.StdEncoding.DecodeString("SUQzBAAAAAABAFRYWFgAAAASAAADbWFqb3JfYnJhbmQAbXA0MgBUWFhYAAAAEQAAA21pbm9yX3Zl")
-	st, err := DetectContentTypeFromReader(bytes.NewReader(mp3))
+	st, err := DetectContentTypeFromReader(bytes.NewReader(mp3), "")
 	require.NoError(t, err)
 	assert.True(t, st.IsAudio())
 }
 
 func TestDetectContentTypeOgg(t *testing.T) {
 	oggAudio, _ := hex.DecodeString("4f67675300020000000000000000352f0000000000007dc39163011e01766f72626973000000000244ac0000000000000071020000000000b8014f6767530000")
-	st, err := DetectContentTypeFromReader(bytes.NewReader(oggAudio))
+	st, err := DetectContentTypeFromReader(bytes.NewReader(oggAudio), "")
 	require.NoError(t, err)
 	assert.True(t, st.IsAudio())
 
 	oggVideo, _ := hex.DecodeString("4f676753000200000000000000007d9747ef000000009b59daf3012a807468656f7261030201001e00110001e000010e00020000001e00000001000001000001")
-	st, err = DetectContentTypeFromReader(bytes.NewReader(oggVideo))
+	st, err = DetectContentTypeFromReader(bytes.NewReader(oggVideo), "")
 	require.NoError(t, err)
 	assert.True(t, st.IsVideo())
 }
@@ -148,7 +148,7 @@ func TestDetectContentTypeAvif(t *testing.T) {
 	avifImage, err := hex.DecodeString("000000206674797061766966")
 	require.NoError(t, err)
 
-	st, err := DetectContentTypeFromReader(bytes.NewReader(avifImage))
+	st, err := DetectContentTypeFromReader(bytes.NewReader(avifImage), "")
 	require.NoError(t, err)
 
 	assert.True(t, st.IsImage())
@@ -158,10 +158,24 @@ func TestDetectContentTypeModelGLB(t *testing.T) {
 	glb, err := hex.DecodeString("676c5446")
 	require.NoError(t, err)
 
-	st, err := DetectContentTypeFromReader(bytes.NewReader(glb))
+	st, err := DetectContentTypeFromReader(bytes.NewReader(glb), "")
 	require.NoError(t, err)
 
 	// print st for debugging
 	assert.Equal(t, "model/gltf-binary", st.GetMimeType())
 	assert.True(t, st.IsGLB())
 }
+
+func TestDetectInterlisp(t *testing.T) {
+	interlisp, err := base64.StdEncoding.DecodeString("ICAKKERFRklORS1GSUxFLUlORk8gHlBBQ0tBR0UgIklOVEVSTElTUCIgHlJFQURUQUJMRSAiSU5URVJMSVNQIiAeQkFTRSAxMCkKCgYB")
+	require.NoError(t, err)
+	st, err := DetectContentTypeFromReader(bytes.NewReader(interlisp), "test")
+	require.NoError(t, err)
+	assert.True(t, st.IsText())
+	st, err = DetectContentTypeFromReader(bytes.NewReader(interlisp), "")
+	require.NoError(t, err)
+	assert.False(t, st.IsText())
+	st, err = DetectContentTypeFromReader(bytes.NewReader(interlisp), "test.lcom")
+	require.NoError(t, err)
+	assert.False(t, st.IsText())
+}
diff --git a/routers/web/repo/editor.go b/routers/web/repo/editor.go
index 5114cc9c05..3e3cb0016d 100644
--- a/routers/web/repo/editor.go
+++ b/routers/web/repo/editor.go
@@ -189,7 +189,7 @@ func editFile(ctx *context.Context, isNewFile bool) {
 		buf = buf[:n]
 
 		// Only some file types are editable online as text.
-		if !typesniffer.DetectContentType(buf).IsRepresentableAsText() {
+		if !typesniffer.DetectContentType(buf, blob.Name()).IsRepresentableAsText() {
 			ctx.NotFound("typesniffer.IsRepresentableAsText", nil)
 			return
 		}
diff --git a/routers/web/repo/render.go b/routers/web/repo/render.go
index b31e2e203a..05eeadc519 100644
--- a/routers/web/repo/render.go
+++ b/routers/web/repo/render.go
@@ -41,7 +41,7 @@ func RenderFile(ctx *context.Context) {
 	n, _ := util.ReadAtMost(dataRc, buf)
 	buf = buf[:n]
 
-	st := typesniffer.DetectContentType(buf)
+	st := typesniffer.DetectContentType(buf, blob.Name())
 	isTextFile := st.IsText()
 
 	rd := charset.ToUTF8WithFallbackReader(io.MultiReader(bytes.NewReader(buf), dataRc), charset.ConvertOpts{})
diff --git a/routers/web/repo/setting/avatar.go b/routers/web/repo/setting/avatar.go
index 84d7cccdb8..20e211316d 100644
--- a/routers/web/repo/setting/avatar.go
+++ b/routers/web/repo/setting/avatar.go
@@ -45,7 +45,7 @@ func UpdateAvatarSetting(ctx *context.Context, form forms.AvatarForm) error {
 	if err != nil {
 		return fmt.Errorf("io.ReadAll: %w", err)
 	}
-	st := typesniffer.DetectContentType(data)
+	st := typesniffer.DetectContentType(data, "")
 	if !st.IsImage() || st.IsSvgImage() {
 		return errors.New(ctx.Locale.TrString("settings.uploaded_avatar_not_a_image"))
 	}
diff --git a/routers/web/repo/setting/lfs.go b/routers/web/repo/setting/lfs.go
index b9cb86bd08..9930d03e8e 100644
--- a/routers/web/repo/setting/lfs.go
+++ b/routers/web/repo/setting/lfs.go
@@ -291,7 +291,7 @@ func LFSFileGet(ctx *context.Context) {
 	}
 	buf = buf[:n]
 
-	st := typesniffer.DetectContentType(buf)
+	st := typesniffer.DetectContentType(buf, "")
 	ctx.Data["IsTextFile"] = st.IsText()
 	isRepresentableAsText := st.IsRepresentableAsText()
 
diff --git a/routers/web/repo/view.go b/routers/web/repo/view.go
index bb3e1388a8..d00f85a134 100644
--- a/routers/web/repo/view.go
+++ b/routers/web/repo/view.go
@@ -228,7 +228,7 @@ func getFileReader(ctx gocontext.Context, repoID int64, blob *git.Blob) ([]byte,
 	n, _ := util.ReadAtMost(dataRc, buf)
 	buf = buf[:n]
 
-	st := typesniffer.DetectContentType(buf)
+	st := typesniffer.DetectContentType(buf, blob.Name())
 	isTextFile := st.IsText()
 
 	// FIXME: what happens when README file is an image?
@@ -262,7 +262,7 @@ func getFileReader(ctx gocontext.Context, repoID int64, blob *git.Blob) ([]byte,
 	}
 	buf = buf[:n]
 
-	st = typesniffer.DetectContentType(buf)
+	st = typesniffer.DetectContentType(buf, blob.Name())
 
 	return buf, dataRc, &fileInfo{st.IsText(), true, meta.Size, &meta.Pointer, st}, nil
 }
diff --git a/routers/web/user/setting/profile.go b/routers/web/user/setting/profile.go
index 400ee71f08..e0ce88b582 100644
--- a/routers/web/user/setting/profile.go
+++ b/routers/web/user/setting/profile.go
@@ -151,7 +151,7 @@ func UpdateAvatarSetting(ctx *context.Context, form *forms.AvatarForm, ctxUser *
 			return fmt.Errorf("io.ReadAll: %w", err)
 		}
 
-		st := typesniffer.DetectContentType(data)
+		st := typesniffer.DetectContentType(data, "")
 		if !st.IsImage() || st.IsSvgImage() {
 			return errors.New(ctx.Locale.TrString("settings.uploaded_avatar_not_a_image"))
 		}