SeleniumHQ/selenium · error · anyhow::Error

Format for file {} cannot be inferred

Error message

Format for file {} cannot be inferred

What it means

Raised in uncompress() (files.rs:143) when the `infer` crate cannot determine the file type from its bytes AND the filename does not end with .pkg or .dmg. Selenium Manager has no fallback to identify the format and aborts. The filename is included in the message.

Source

Thrown at rust/src/files.rs:143

pub fn uncompress(
    compressed_file: &str,
    target: &Path,
    log: &Logger,
    os: &str,
    single_file: Option<String>,
    volume: Option<&str>,
) -> Result<(), Error> {
    let mut extension = match infer::get_from_path(compressed_file)? {
        Some(kind) => kind.extension(),
        _ => {
            if compressed_file.ends_with(PKG) || compressed_file.ends_with(DMG) {
                if MACOS.is(os) {
                    PKG
                } else {
                    return Err(anyhow!(format_one_arg(UNCOMPRESS_MACOS_ERR_MSG, PKG)));
                }
            } else {
                return Err(anyhow!(format!(
                    "Format for file {} cannot be inferred",
                    compressed_file
                )));
            }
        }
    };
    if compressed_file.ends_with(DMG) {
        if MACOS.is(os) {
            extension = DMG;
        } else {
            return Err(anyhow!(format_one_arg(UNCOMPRESS_MACOS_ERR_MSG, DMG)));
        }
    }
    log.trace(format!(
        "The detected extension of the compressed file is {}",
        extension
    ));

View on GitHub (pinned to aa36b38e69)

Solutions

1. Re-download the file; partial downloads are the most common cause.
2. Inspect the file with `file <path>` and check its size is non-zero.
3. Verify the download URL points to a real archive endpoint, not an error page.
4. If the format is genuinely unsupported, convert it upstream to zip/tar.gz.

# Bash: verify the downloaded file is non-empty and a known archive before extraction
if [ ! -s "$FILE" ]; then echo "Empty/truncated download"; exit 1; fi
file "$FILE"

match uncompress(file, target, &log, os, single, vol) {
    Ok(()) => (),
    Err(e) if e.to_string().contains("cannot be inferred") => {
        eprintln!("Re-download {}; possibly truncated", file);
        return Err(e);
    }
    Err(e) => return Err(e),
}

When it happens

Trigger: infer::get_from_path returns None and the filename extension is neither PKG nor DMG. The else branch at line 142 returns the error. Typical when the downloaded file is empty, a truncated download, or an unsupported format.

Common situations: A partial/empty download (network drop produced 0 bytes); the server returned an HTML error page saved with a driver filename; an unsupported container (e.g. zstd, rar); filesystem gave 0 bytes.

Related errors

• Downloaded file cannot be uncompressed ({} extension)
• Wrong browser/driver version
• Unsuccessful response ({}) for URL {}
• Error parsing JSON from URL {} {}
• Unsafe entry (path traversal): {:?}

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/1de640b985f2e1c5. Report an issue: GitHub.