mongodb/node-mongodb-native · error · MongoDecompressionError

Server sent message compressed using an unsupported…

Error message

Server sent message compressed using an unsupported compressor. (Received compressor ID ${compressorID})

What it means

Thrown by decompress() in the wire protocol layer when a server response arrives marked as OP_COMPRESSED but carries a compressorID byte outside the recognized set (0=none, 1=snappy, 2=zlib, 3=zstd). The driver cannot decode the payload because no handler exists for that ID, so the entire response is unusable. It surfaces as a MongoDecompressionError. This typically indicates byte corruption on the wire, a man-in-the-middle/proxy rewriting frames, or a server using a compressor the client driver version does not yet support.

Solutions

1. Remove or empty the 'compressors' option in your MongoClientOptions so compression is not negotiated (fastest workaround).
2. Upgrade the mongodb driver to the latest version in case the compressor ID is newly supported.
3. Disable any proxy, sidecar, or packet inspector between the client and mongod/mongos and retest against the server directly.
4. Capture the traffic and confirm the server's hello response compressor list; if it advertises an ID the driver cannot handle, upgrade or reconfigure mongod.
5. Open a MongoDB server ticket if a stable server advertises a compressor ID absent from the driver's Compressor map.

Example fix

// before
const client = new MongoClient(uri, { compressors: ['zstd'] });

// after (disable compression to isolate the failure)
const client = new MongoClient(uri);

try {
  await collection.find({}).toArray();
} catch (error) {
  if (error instanceof MongoDecompressionError) {
  }
}

When it happens

Trigger: Occurs only when compression is enabled in client options (compressors: ['zlib'|'snappy'|'zstd']) AND the server agreed to compress AND a returned OP_COMPRESSED frame's compressorID byte at offset headerSize+8 is not 0,1,2, or 3. Fires inside decompressResponse -> decompress at src/cmap/wire_protocol/compression.ts:120 during response reading on any compressed command.

Common situations: A corporate proxy or load balancer (e.g. HAProxy with protobuf-aware rewriting, a debugging MITM) mangles MongoDB wire frames; running against a prerelease/newer server that introduced a new compressor before the driver shipped support; network hardware bit-flips; a stale connection pool reusing a socket after the server changed its compression config mid-session.

Related errors

• Message body and message header must be the same length
• is not a valid compression mechanism. Must be one of: .
• compressors must be an array or a comma-delimited list of…
• OP_REPLY numberReturned is an invalid array length
• Unknown compressor failed to compress

AI-assisted analysis of mongodb/node-mongodb-native@dce7939f86 (2026-08-11). Data as JSON: /api/errors/c2ae303ccf04a388. Report an issue: GitHub.

Appendix: source

Thrown at src/cmap/wire_protocol/compression.ts:120

      throw new MongoInvalidArgumentError(
        `Unknown compressor ${options.agreedCompressor} failed to compress`
      );
    }
  }
}

// Decompress a message using the given compressor
export async function decompress(
  compressorID: number,
  compressedData: Uint8Array
): Promise<Uint8Array> {
  if (
    compressorID !== Compressor.snappy &&
    compressorID !== Compressor.zstd &&
    compressorID !== Compressor.zlib &&
    compressorID !== Compressor.none
  ) {
    throw new MongoDecompressionError(
      `Server sent message compressed using an unsupported compressor. (Received compressor ID ${compressorID})`
    );
  }

  switch (compressorID) {
    case Compressor.snappy: {
      Snappy ??= loadSnappy();
      return await Snappy.uncompress(compressedData, { asBuffer: true });
    }
    case Compressor.zstd: {
      loadZstd();
      if ('kModuleError' in zstd) {
        throw zstd['kModuleError'];
      }
      return await zstd.decompress(compressedData);
    }
    case Compressor.zlib: {
      return await zlibInflate(compressedData);

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