skylot/jadx · error · IOException

Failed to open zip: {}

Error message

Failed to open zip: {}

What it means

Thrown by ZipReader.open inside the generic catch block: when an exception (other than FallbackException) occurs AND the options contain ZipReaderFlags.DONT_USE_FALLBACK, jadx rethrows as IOException with message 'Failed to open zip: <file>' chaining the original cause. Without that flag jadx would instead silently switch to the fallback parser.

Source

Thrown at jadx-commons/jadx-zip/src/main/java/jadx/zip/ZipReader.java:55

	public ZipReader(ZipReaderOptions options) {
		this.options = options;
	}

	@SuppressWarnings("resource")
	public ZipContent open(File zipFile) throws IOException {
		if (!zipFile.exists()) {
			throw new FileNotFoundException(zipFile.getAbsolutePath());
		}
		try {
			JadxZipParser jadxParser = new JadxZipParser(zipFile, options);
			IZipParser detectedParser = detectParser(zipFile, jadxParser);
			return detectedParser.open();
		} catch (FallbackException e) {
			throw e;
		} catch (Exception e) {
			if (options.getFlags().contains(ZipReaderFlags.DONT_USE_FALLBACK)) {
				throw new IOException("Failed to open zip: " + zipFile, e);
			}
			// switch to fallback parser
			return buildFallbackParser(zipFile).open();
		}
	}

	/**
	 * Visit valid entries in a zip file.
	 * Return not null value from visitor to stop iteration.
	 */
	public <R> @Nullable R visitEntries(File file, Function<IZipEntry, R> visitor) {
		try (ZipContent content = open(file)) {
			for (IZipEntry entry : content.getEntries()) {
				R result = visitor.apply(entry);
				if (result != null) {
					return result;
				}
			}

View on GitHub (pinned to e738a26571)

Solutions

1. If fallback is acceptable, do NOT set ZipReaderFlags.DONT_USE_FALLBACK so jadx can retry with the fallback parser.
2. Verify the input is a valid zip (unzip -t or a zip integrity check).
3. Re-download or rebuild the archive if corrupt.
4. Inspect the chained cause for the specific parse failure.

Example fix

// before
ZipReaderOptions opts = new ZipReaderOptions(security,
    ZipReaderFlags.of(ZipReaderFlags.DONT_USE_FALLBACK));
new ZipReader(opts).open(file);
// after
ZipReaderOptions opts = new ZipReaderOptions(security, ZipReaderFlags.none());
new ZipReader(opts).open(file);

// Decide upfront whether fallback is acceptable for your use case
boolean strict = mustValidateOnly();
ZipReaderFlags flags = strict ? ZipReaderFlags.of(ZipReaderFlags.DONT_USE_FALLBACK) : ZipReaderFlags.none();
ZipReader reader = new ZipReader(new ZipReaderOptions(security, flags));

public static boolean canOpenWithoutFallback(ZipReader r, File f) {
    try { r.open(f); return true; } catch (IOException e) { return false; }
}

try {
    reader.open(file);
} catch (IOException e) {
    if (e.getMessage().startsWith("Failed to open zip")) {
        // retry with fallback enabled
        ZipReaderOptions relaxed = new ZipReaderOptions(security, ZipReaderFlags.none());
        new ZipReader(relaxed).open(file);
    } else throw e;
}

When it happens

Trigger: Opening a zip/apk that the primary JadxZipParser cannot parse (corrupt, unusual format, unsupported compression), while the caller has requested DONT_USE_FALLBACK so the fallback parser is bypassed.

Common situations: Corrupted or truncated APK/JAR; intentionally malformed test input; zip using features the jadx parser rejects; caller explicitly disabled fallback for strict validation.

Related errors

• {}
• Failed to process zip file: {}
• Failed to process zip entry: {}
• Failed to save JSON file: {}
• Failed to save JSON file: {}

AI-assisted analysis of skylot/jadx@e738a26571 (2026-08-14). Data as JSON: /api/errors/ae9e57c85e9d733a. Report an issue: GitHub.