What is MIME type "application/pgp-signature"?

A MIME type is a string that tells browsers and other tools how to handle a particular kind of file.

application/pgp-signature holds digital signatures.
It confirms a file's authenticity and integrity using cryptographic methods.
The signature is produced by OpenPGP tools. It accompanies another file to verify that its content is unaltered.
Files using this MIME type usually have extensions like ASC or SIG.

Use Case: Verifying email attachments and documents.
Use Case: Securing software downloads.
Key Fact: It only contains signature data, not the content itself.
Key Fact: It follows the OpenPGP standard for encryption.

For more details, please visit IANA Media Types Reference.

Associated file extensions

.asc, .sig

Usage Examples

HTTP Header

When serving content with this MIME type, set the Content-Type header:


    Content-Type: application/pgp-signature

HTML

In HTML, you can specify the MIME type in various elements:


    <a href="file.dat" type="application/pgp-signature">Download file</a>

Server-side (Node.js)

Setting the Content-Type header in Node.js:


    const http = require('http');    
    
    http.createServer((req, res) => {    
      res.setHeader('Content-Type', 'application/pgp-signature');    
      res.end('Content here');    
    }).listen(3000);

Associated file extensions

.asc, .sig

FAQs

What is the purpose of an application/pgp-signature file?

This MIME type represents a "detached signature" used to verify that a file has not been altered and comes from a trusted source. It contains cryptographic data generated by OpenPGP software and is usually paired with a specific software download or document. Common extensions include .asc (Armored) and .sig (Binary).

How do I open or view a .sig or .asc file?

You typically do not "open" these files to read content; instead, you use them with PGP software like GnuPG (GPG) to verify another file. If you open an .asc file in a text editor like Notepad, you will see a text block starting with -----BEGIN PGP SIGNATURE-----, whereas a .sig file is usually binary.

How do I configure Apache to serve PGP signatures correctly?

You should ensure the server sends the correct Content-Type header to prevent browsers from misinterpreting the file as plain text. Add the following line to your .htaccess file or main configuration: AddType application/pgp-signature .sig .asc.

How do I configure Nginx for application/pgp-signature?

Update your mime.types file or the types block in your server configuration. Add the line application/pgp-signature sig asc; to ensure Nginx serves both extensions with the correct MIME type.

Why does my browser download the .asc file instead of displaying it?

Browsers are configured to handle application/pgp-signature as a download rather than inline content because it is not a renderable document or image. This behavior ensures you save the signature to disk, allowing you to run verification commands like gpg --verify against the associated file.

What is the difference between application/pgp-signature and application/pgp-encrypted?

application/pgp-signature contains only the digital signature used to prove the authenticity of a separate file. In contrast, application/pgp-encrypted contains the actual message or file content that has been scrambled to prevent unauthorized reading.

How can I verify a file using this signature type?

You need the signer's public key imported into your keychain and a tool like GnuPG. Run the command gpg --verify filename.sig filename.ext in your terminal; if the output confirms a "Good signature," the downloaded file is authentic and unaltered.

General FAQ

What is a MIME type?

A MIME (Multipurpose Internet Mail Extensions) type is a standard that indicates the nature and format of a document, file, or assortment of bytes. MIME types are defined and standardized in IETF's RFC 6838.

MIME types are important because they help browsers and servers understand how to process a file. When a browser receives a file from a server, it uses the MIME type to determine how to display or handle the content, whether it's an image to display, a PDF to open in a viewer, or a video to play.

MIME types consist of a type and a subtype, separated by a slash (e.g., text/html, image/jpeg, application/pdf). Some MIME types also include optional parameters.

How do I find the MIME type for a file?

You can check the file extension or use a file identification tool such as file --mime-type on the command line. Many programming languages also provide libraries to detect MIME types.

Why are multiple MIME types listed for one extension?

Different applications and historical conventions may use alternative MIME identifiers for the same kind of file. Showing them all helps ensure compatibility across systems.