Serve security.txt as text/plain with utf-8

Why it matters

RFC 9116 requires the file to be sent as text/plain in utf-8. Tools may reject it if the server labels it as html, binary or another charset.

The fix

1. Check what the server sends with curl -sI https://example.com/.well-known/security.txt and look at the Content-Type line.
2. Serve the file as a static file named security.txt with the type text/plain; charset=utf-8. A page built by a framework route or a catch-all rewrite to index.html is the usual cause of text/html.
3. Save the file itself as utf-8 without special characters in the wrong encoding.

curl -sI https://example.com/.well-known/security.txt | grep -i content-type

The examples use example.com. Replace it with your own domain.

Read the documentation ↗(opens in a new tab)

Related

• Reported by the security.txt check
• Publish a security.txt file
• Serve security.txt from /.well-known/
• Serve security.txt over https
• Add a Contact line to security.txt
• Fix the Contact value in security.txt
• Add an Expires line to security.txt
• Use an RFC 3339 date in the Expires line
• Renew the expired security.txt
• Renew security.txt before it expires
• Shorten the security.txt Expires date
• Fix repeated or insecure fields in security.txt
• Make the Canonical line match where the file is served