Incomplete or Corrupted Download? Causes and How to Fix It

You download a file, and it will not open, will not install or says it is incomplete. Here is why, and how to fix it.

Common causes of a corrupted download

• Unstable internet or Wi-Fi.
• Download interrupted or cancelled.
• Browser or extension interference.
• Not enough disk space.
• Server problems or a broken source file.
• Antivirus software blocking part of the download.
• Proxy or VPN issues.

How to tell if a download is incomplete

1. Compare file sizes. The size on disk should match the size listed on the download page.
2. Look for temporary extensions such as .crdownload or .part. They mean the download is not finished.
3. Try opening it. Errors such as "unexpected end of file" or "archive is damaged" are classic signs.

Verify with a checksum

Many sites publish a SHA-256 checksum. Compute your file's value and compare.

• Windows: certutil -hashfile file.zip SHA256
• Mac: shasum -a 256 file.zip
• Linux: sha256sum file.zip

If the values differ even by one character, the file is damaged. Download it again.

How to fix it

1. Delete and re-download. This works most of the time.
2. Use a stable connection, preferably wired.
3. Free up disk space before downloading large files.
4. Try another browser or disable extensions.
5. Use a download manager that can resume interrupted downloads.
6. Resume with a command line tool:

curl -C - -O https://example.com/file.zip

1. Temporarily check antivirus settings, and only for files from sources you trust.
2. Try repair tools for ZIP and other formats. See how to fix a corrupted file.

For developers: test your download handling

If you build an app that downloads files, test what happens when a download stops halfway. Create a truncated or corrupted sample using CorruptAnyFile and confirm your software detects it, shows a clear error and offers a retry. Read more in why developers corrupt files for testing.

Related reading

What corrupts a file, what a corrupt file is and how to tell if a file is corrupted.

FAQ

Why is my downloaded file corrupted? Usually an interrupted or unstable connection.

How do I check a download is complete? Compare the size and the checksum.

Can I resume a broken download? Yes, with a download manager or curl.