diff --git a/github.go b/github.go
index fe862e3..326e159 100644
--- a/github.go
+++ b/github.go
@@ -49,7 +49,7 @@ func findGitHubREADME(u *url.URL) (*source, error) {
 		}
 
 		if resp.StatusCode == http.StatusOK {
-			return &source{resp.Body, result.DownloadURL}, nil
+			return &source{reader: resp.Body, URL: result.DownloadURL}, nil
 		}
 	}
 
diff --git a/gitlab.go b/gitlab.go
index 68256be..5b3cb5f 100644
--- a/gitlab.go
+++ b/gitlab.go
@@ -53,7 +53,7 @@ func findGitLabREADME(u *url.URL) (*source, error) {
 		}
 
 		if resp.StatusCode == http.StatusOK {
-			return &source{resp.Body, readmeRawURL}, nil
+			return &source{reader: resp.Body, URL: readmeRawURL}, nil
 		}
 	}
 
diff --git a/glow_test.go b/glow_test.go
index 8743be2..7353a17 100644
--- a/glow_test.go
+++ b/glow_test.go
@@ -1,6 +1,9 @@
 package main
 
 import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
 	"testing"
 )
 
@@ -39,3 +42,53 @@ func TestGlowFlags(t *testing.T) {
 		}
 	}
 }
+
+func TestSourceDetectsExtensionlessJSONContentType(t *testing.T) {
+	src := source{
+		URL:         "https://api.example.com/endpoint",
+		contentType: "application/vnd.api+json; charset=utf-8",
+	}
+
+	if !src.isCode() {
+		t.Fatal("expected extensionless JSON response to render as code")
+	}
+	if got := src.codeBlockLanguage(); got != ".json" {
+		t.Fatalf("expected .json code block language, got %q", got)
+	}
+}
+
+func TestSourceMarkdownExtensionTakesPrecedenceOverContentType(t *testing.T) {
+	src := source{
+		URL:         "https://example.com/README.md",
+		contentType: "application/json",
+	}
+
+	if src.isCode() {
+		t.Fatal("expected markdown extension to render as markdown")
+	}
+}
+
+func TestSourceFromArgRecordsHTTPContentType(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		fmt.Fprint(w, `{"ok":true}`)
+	}))
+	t.Cleanup(server.Close)
+
+	src, err := sourceFromArg(server.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		if err := src.reader.Close(); err != nil {
+			t.Fatal(err)
+		}
+	})
+
+	if got := src.contentType; got != "application/json; charset=utf-8" {
+		t.Fatalf("expected content type to be recorded, got %q", got)
+	}
+	if !src.isCode() {
+		t.Fatal("expected extensionless JSON HTTP source to render as code")
+	}
+}
diff --git a/main.go b/main.go
index b31ca15..7e167c2 100644
--- a/main.go
+++ b/main.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"io/fs"
+	"mime"
 	"net/http"
 	"net/url"
 	"os"
@@ -67,8 +68,9 @@ var (
 
 // source provides a readable markdown source.
 type source struct {
-	reader io.ReadCloser
-	URL    string
+	reader      io.ReadCloser
+	URL         string
+	contentType string
 }
 
 // sourceFromArg parses an argument and creates a readable source for it.
@@ -99,7 +101,11 @@ func sourceFromArg(arg string) (*source, error) {
 			if resp.StatusCode != http.StatusOK {
 				return nil, fmt.Errorf("HTTP status %d", resp.StatusCode)
 			}
-			return &source{resp.Body, u.String()}, nil
+			return &source{
+				reader:      resp.Body,
+				URL:         u.String(),
+				contentType: resp.Header.Get("Content-Type"),
+			}, nil
 		}
 	}
 
@@ -123,7 +129,7 @@ func sourceFromArg(arg string) (*source, error) {
 					}
 
 					u, _ := filepath.Abs(path)
-					src = &source{r, u}
+					src = &source{reader: r, URL: u}
 
 					// abort filepath.Walk
 					return errors.New("source found")
@@ -147,7 +153,34 @@ func sourceFromArg(arg string) (*source, error) {
 	if err != nil {
 		return nil, fmt.Errorf("unable to get absolute path: %w", err)
 	}
-	return &source{r, u}, nil
+	return &source{reader: r, URL: u}, nil
+}
+
+func (s source) isCode() bool {
+	if !utils.IsMarkdownFile(s.URL) {
+		return true
+	}
+	return filepath.Ext(s.URL) == "" && s.codeBlockLanguage() != ""
+}
+
+func (s source) codeBlockLanguage() string {
+	if ext := filepath.Ext(s.URL); ext != "" {
+		return ext
+	}
+	return codeBlockLanguageFromContentType(s.contentType)
+}
+
+func codeBlockLanguageFromContentType(contentType string) string {
+	mediaType, _, err := mime.ParseMediaType(contentType)
+	if err != nil {
+		mediaType = strings.TrimSpace(strings.Split(contentType, ";")[0])
+	}
+	mediaType = strings.ToLower(mediaType)
+
+	if mediaType == "application/json" || strings.HasSuffix(mediaType, "+json") {
+		return ".json"
+	}
+	return ""
 }
 
 // validateStyle checks if the style is a default style, if not, checks that
@@ -288,7 +321,7 @@ func executeCLI(cmd *cobra.Command, src *source, w io.Writer) error {
 		baseURL = u.String() + "/"
 	}
 
-	isCode := !utils.IsMarkdownFile(src.URL)
+	isCode := src.isCode()
 
 	// initialize glamour
 	r, err := glamour.NewTermRenderer(
@@ -303,7 +336,7 @@ func executeCLI(cmd *cobra.Command, src *source, w io.Writer) error {
 	}
 
 	content := string(b)
-	ext := filepath.Ext(src.URL)
+	ext := src.codeBlockLanguage()
 	if isCode {
 		content = utils.WrapCodeBlock(string(b), ext)
 	}