pxb1988/dex2jar · error · DexException

Endian_tag unsupported

Error message

Endian_tag unsupported

What it means

After the magic check, DexFileReader reads the endian_tag field from the DEX header and requires it to equal ENDIAN_CONSTANT (0x12345678, little-endian). This DexException is thrown when the file declares any other endianness (e.g. REVERSE_ENDIAN_CONSTANT 0x78563412, big-endian dex), which the reader cannot decode. The file is structurally a dex but byte-ordered in a way this library does not support.

Solutions

1. Rebuild/re-export the dex with standard little-endian tooling (dx/d8) so endian_tag = 0x12345678
2. Hexdump the header and verify offset 0x28 (8 magic + 4 checksum + 20 signature + 4 file_size + 4 header_size) contains 78 56 34 12
3. Re-obtain the file if the header region appears corrupted
4. If you truly have a big-endian dex, byte-swap it or use a reader that supports REVERSE_ENDIAN_CONSTANT

Example fix

// before (hexdump at endian_tag offset)
// 12 34 56 78 -> ok; 78 56 34 12 -> throws
// after: rebuild with d8
// d8 --output . classes/*.class  # produces little-endian classes.dex

static boolean hasStandardEndian(byte[] dex) {
    if (dex == null || dex.length < 8 + 4 + 20 + 4 + 4 + 4) return false;
    int off = 8 + 4 + 20 + 4 + 4; // magic + checksum + signature + file_size + header_size
    int tag = (dex[off] & 0xFF) | (dex[off+1] & 0xFF) << 8
            | (dex[off+2] & 0xFF) << 16 | (dex[off+3] & 0xFF) << 24;
    return tag == 0x12345678;
}

try {
    new DexFileReader(file);
} catch (DexException e) {
    if (e.getMessage().contains("Endian_tag")) {
        throw new UnsupportedOperationException("Big-endian DEX not supported: " + file, e);
    }
    throw e;
}

When it happens

Trigger: Opening a big-endian DEX (endian_tag 0x78563412) produced by tools targeting big-endian environments, or a file whose header is misaligned/corrupted so the 4 bytes read as an unexpected endian tag.

Common situations: DEX files from unusual toolchains or converted archives; header corruption from a bad transfer; hand-crafted dex for research that uses the reverse endian tag.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• Odex unsupported.
• Magic unsupported.
• The source file is not a .dex or .zip file
• the src file not a .dex or zip file
• Encountered RESTART_LOCAL on new v

AI-assisted analysis of pxb1988/dex2jar@b5bda4fb49 (2026-09-08). Data as JSON: /api/errors/bf2faa98e9456784. Report an issue: GitHub.

Appendix: source

Thrown at dex-reader/src/main/java/com/googlecode/d2j/reader/DexFileReader.java:181

        } else {
            throw new DexException("Magic unsupported.");
        }
        int version = in.getInt() >> 8;
        if (version < DEX_035 || version > DEX_040) {
            System.err.println("Unknown DEX version. Trying anyway...");
        }
        this.dex_version = version;
        in.order(ByteOrder.LITTLE_ENDIAN);

        // skip uint checksum
        // and 20 bytes signature
        // and uint file_size
        // and uint header_size 0x70
        skip(in, 4 + 20 + 4 + 4);

        int endian_tag = in.getInt();
        if (endian_tag != ENDIAN_CONSTANT) {
            throw new DexException("Endian_tag unsupported");
        }

        // skip uint link_size
        // and uint link_off
        skip(in, 4 + 4);

        int map_off = in.getInt();

        string_ids_size = in.getInt();
        int string_ids_off = in.getInt();
        type_ids_size = in.getInt();
        int type_ids_off = in.getInt();
        proto_ids_size = in.getInt();
        int proto_ids_off = in.getInt();
        field_ids_size = in.getInt();
        int field_ids_off = in.getInt();
        method_ids_size = in.getInt();
        int method_ids_off = in.getInt();

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