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.ASC file extension

To open .ASC files on Windows, right-click the .ASC file and choose Open with; if you are unsure what it is, open it first in Notepad or another text editor and check the "BEGIN PGP" header.

To open a .ASC file, use an OpenPGP-compatible tool such as GnuPG, Gpg4win/Kleopatra on Windows, or Thunderbird where appropriate. If you only need to inspect it, open it in a text editor and look for headers such as "-----BEGIN PGP SIGNATURE-----", "-----BEGIN PGP PUBLIC KEY BLOCK-----", or "-----BEGIN PGP MESSAGE-----".

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Last updated: April 29, 2026 · Reviewed by Julian Stricker

Open on your device

Choose your operating system for a dedicated step-by-step opening guide.

How to open .ASC files

Use these platform-specific instructions to open .ASC files safely.

Windows

  1. Right-click the .ASC file and choose Open with; if you are unsure what it is, open it first in Notepad or another text editor and check the "BEGIN PGP" header.
  2. For OpenPGP use, install or open it with Gpg4win/Kleopatra or GnuPG, then choose the relevant action: import a key, decrypt a message, or verify a signature.
  3. If the .ASC file is a detached signature for a download, keep it in the same folder as the original file and verify it with Kleopatra or GnuPG rather than trying to run it.
Full Windows guide

Mac

  1. Control-click the .ASC file and choose Open With > TextEdit to inspect the header if needed.
  2. Use GnuPG or another OpenPGP-compatible desktop tool to import keys, decrypt messages, or verify signatures.
  3. For a detached signature, make sure you also have the original file being verified; the .ASC file alone is not enough.
Full Mac guide

Linux

  1. Open the file in a text editor or run a file-identification tool to confirm it is OpenPGP ASCII armor.
  2. Use GnuPG from the terminal for common actions, for example: "gpg --import file.asc" for a key, "gpg --verify file.asc original-file" for a detached signature, or "gpg --decrypt file.asc" for an encrypted message.
  3. If using a graphical file manager, choose an installed OpenPGP-compatible application when prompted.
Full Linux guide

iOS

  1. iOS does not provide a general built-in OpenPGP handler for .ASC files; Files or a text viewer may only preview the armored text.
  2. For reliable importing, verification, or decryption, transfer the file to a desktop system with GnuPG, Gpg4win/Kleopatra, or another OpenPGP-compatible tool.
Full iOS guide

Android

  1. Android may display the .ASC file as text, but it typically will not verify or decrypt it without an OpenPGP-compatible app.
  2. If you only need to identify it, open it as text and check the "BEGIN PGP" header; for full OpenPGP operations, use a trusted OpenPGP tool or transfer it to a desktop system.
Full Android guide

Security notes

  • A .ASC file can contain a private key block. Treat any file beginning with "-----BEGIN PGP PRIVATE KEY BLOCK-----" as highly sensitive and do not upload, share, or import it on untrusted devices.
  • A detached .ASC signature is useful only when you verify it with the exact file it signs and the correct public key. Simply having a .ASC file next to a download does not prove the download is safe.
  • Importing a public key from a .ASC file does not verify the identity of its owner. Always check the key fingerprint through a trusted source before relying on it.
  • Do not edit, rewrap, or save changes to armored PGP text unless instructed by your OpenPGP tool; even small changes can make signatures, keys, or encrypted messages unusable.

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Can't open this file?

These are the most common causes and fixes when .ASC files fail to open.

Common reasons

  • The file opens as a block of strange text
  • Signature verification fails
  • Decryption asks for a secret key or passphrase
  • A public key imports but is not trusted

Fix steps

  1. Check the first line to identify the type, such as PGP MESSAGE, PGP PUBLIC KEY BLOCK, PGP PRIVATE KEY BLOCK, or PGP SIGNATURE.
  2. Use OpenPGP software for the correct action: import, decrypt, or verify.
  3. Do not edit and save the text unless you know what you are doing, because small changes can corrupt the data.

OS-specific troubleshooting

What is a .ASC file?

A .ASC file is usually an ASCII-armored OpenPGP file. OpenPGP ASCII Armor represents binary PGP data as printable text, with header lines that identify whether the file is a message, public key, private key, or signature. IANA and freedesktop shared MIME data associate .asc files with OpenPGP keys, signatures, and encrypted data, depending on the file contents.

Background

.ASC is an ambiguous-looking extension because it suggests plain ASCII text, but in common desktop file associations it is strongly associated with OpenPGP ASCII Armor. These files are used to exchange public keys, store exported certificates, distribute detached signatures for downloads, or send encrypted messages in a text-friendly form.

An ASCII-armored OpenPGP file normally starts with a readable line such as "-----BEGIN PGP MESSAGE-----", "-----BEGIN PGP PUBLIC KEY BLOCK-----", "-----BEGIN PGP PRIVATE KEY BLOCK-----", or "-----BEGIN PGP SIGNATURE-----". Because the content is text, you can view it in a text editor, but viewing is not the same as importing a key, verifying a signature, or decrypting a message.

In practical use, .asc files often appear next to software downloads as signature files. In that case, the .asc file is not the program itself; it is used with OpenPGP software and the original downloaded file to check authenticity and integrity.

Common MIME types: application/pgp-keys

Further reading

Authoritative resources for more details on the .ASC format.

Common .ASC issues

The file opens as a block of strange text

That is normal for ASCII-armored OpenPGP data. The text is an encoded key, message, or signature, not something a word processor can interpret meaningfully.

  1. Check the first line to identify the type, such as PGP MESSAGE, PGP PUBLIC KEY BLOCK, PGP PRIVATE KEY BLOCK, or PGP SIGNATURE.
  2. Use OpenPGP software for the correct action: import, decrypt, or verify.
  3. Do not edit and save the text unless you know what you are doing, because small changes can corrupt the data.

Signature verification fails

A detached .ASC signature must match the exact original file and requires the correct signer public key. Verification fails if the download changed, the wrong file is selected, or the key is missing or untrusted.

  1. Make sure you have both files: the original download and its matching .ASC signature.
  2. Import the signer's public key from a trusted source.
  3. Verify the signature against the original file, not against the .ASC file by itself.
  4. If verification still fails, re-download both files from the official source.

Decryption asks for a secret key or passphrase

An encrypted OpenPGP .ASC message can only be decrypted with the matching private key, and the private key may also be protected by a passphrase.

  1. Confirm that the message was encrypted to one of your public keys.
  2. Make sure the corresponding private key is available in your OpenPGP keyring.
  3. Enter the correct private-key passphrase when prompted.

A public key imports but is not trusted

Importing a public key only adds it to your keyring. It does not prove that the key really belongs to the person or project named in it.

  1. Compare the key fingerprint with a value published through a trusted channel.
  2. Do not rely only on the file name or email address shown in the key.
  3. Follow your OpenPGP tool's trust or certification workflow after verifying the fingerprint.

FAQ

Is a .ASC file just a text file?

It is text-encoded, so you can view it in a text editor, but it usually represents structured OpenPGP data such as a key, encrypted message, or signature.

How do I know what kind of .ASC file I have?

Open it in a text editor and read the first armor header. Common examples are "BEGIN PGP MESSAGE" for encrypted or signed data, "BEGIN PGP PUBLIC KEY BLOCK" for a public key, "BEGIN PGP PRIVATE KEY BLOCK" for a private key, and "BEGIN PGP SIGNATURE" for a detached signature.

Can I convert a .ASC file by renaming it?

No. Renaming only changes the file name. Use an OpenPGP tool such as GnuPG or Kleopatra to export, import, decrypt, verify, or de-armor the data as needed.

Is .ASC the same as .SIG?

Not exactly. GnuPG commonly uses .asc or .sig for detached signatures, but .asc can also contain OpenPGP keys or encrypted messages.

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