QL-Win/QuickLook · error · InvalidDataException

The file does not have a minidump signature.

Error message

The file does not have a minidump signature.

What it means

Thrown after the 32-byte header is read: the Signature field (first UInt32) did not equal MinidumpSignature (0x504D444D, ASCII 'MDMP'). Every legitimate Windows minidump begins with 'MDMP', so a mismatch means the file is not a minidump despite being large enough.

Source

Thrown at QuickLook.Plugin/QuickLook.Plugin.DumpViewer/MinidumpReader.cs:113

    {
        if (fileLength < HeaderSize)
            throw new InvalidDataException("The file is too small to be a minidump.");

        reader.BaseStream.Position = 0;

        var header = new MinidumpHeader
        {
            Signature = reader.ReadUInt32(),
            Version = reader.ReadUInt32(),
            NumberOfStreams = reader.ReadUInt32(),
            StreamDirectoryRva = reader.ReadUInt32(),
            CheckSum = reader.ReadUInt32(),
            TimeDateStamp = reader.ReadUInt32(),
            Flags = reader.ReadUInt64(),
        };

        if (header.Signature != MinidumpSignature)
            throw new InvalidDataException("The file does not have a minidump signature.");

        var directoryBytes = (long)header.NumberOfStreams * DirectoryEntrySize;
        if (!CanRead(fileLength, header.StreamDirectoryRva, directoryBytes))
            throw new InvalidDataException("The minidump stream directory is outside the file.");

        return header;
    }

    private static IEnumerable<MinidumpDirectory> ReadDirectories(BinaryReader reader, long fileLength, MinidumpHeader header)
    {
        reader.BaseStream.Position = header.StreamDirectoryRva;

        for (var i = 0; i < header.NumberOfStreams; i++)
        {
            var directory = new MinidumpDirectory
            {
                Type = (MinidumpStreamType)reader.ReadUInt32(),
                DataSize = reader.ReadUInt32(),

View on GitHub (pinned to cb5d9c429c)

Solutions

1. Use MinidumpReader.IsMinidump(path) — it reads only the first UInt32 and compares to 0x504D444D — before attempting full parse.
2. Verify the producer: generate dumps with tools that emit MDMP (Task Manager 'Create dump file', procdump, WER, or DbgHelp MiniDumpWriteDump).
3. Catch InvalidDataException in the preview host and treat as 'unsupported format'.
4. If a different dump format is intended, route to the correct reader instead of MinidumpReader.

Example fix

// before
var header = ReadHeader(reader, stream.Length);

// after
if (!MinidumpReader.IsMinidump(path)) return;
var header = ReadHeader(reader, stream.Length);

if (!MinidumpReader.IsMinidump(path)) return; // checks first 4 bytes == 'MDMP'

static bool HasMdmpSignature(byte[] head) => head.Length >= 4 && head[0]=='M' && head[1]=='D' && head[2]=='M' && head[3]=='P';

try { var info = MinidumpReader.Read(path); }
catch (InvalidDataException ex) when (ex.Message.Contains("signature")) { /* unsupported format */ }

When it happens

Trigger: ReadHeader reads the first 4 bytes and they are not 0x504D444D. Typical when a full-size non-dump file (e.g. a large .exe, .pdb, or text log misnamed .dmp) is fed to the reader.

Common situations: A user renamed an arbitrary file to .dmp; a debugger wrote a different format (e.g. a 'triage' or a raw memory snapshot without the MDMP header); a full-user-dump from a non-Microsoft tool that uses a custom container.

Related errors

• The file is too small to be a minidump.
• The minidump stream directory is outside the file.
• DOS header not found.
• Thumbs.db not found.
• DS_Store: unknown record type '{stype}'

AI-assisted analysis of QL-Win/QuickLook@cb5d9c429c (2026-08-13). Data as JSON: /api/errors/3f31e9d3e029e6aa. Report an issue: GitHub.