.NET 11 Adds Native Zstandard Compression to System.IO.Compression

.NET developers who needed Zstandard compression have relied on third-party wrappers like ZstdSharp or ZstdNet for years. Starting with .NET 11 Preview 1, that changes: System.IO.Compression now ships ZstandardStream, ZstandardEncoder, and ZstandardDecoder as first-class APIs, no NuGet detour required.

Why Zstandard Matters

Zstandard (zstd), developed by Meta, sits in a sweet spot between speed and ratio. Internal benchmarks from the .NET team show it compresses 2-7x faster than Brotli and Deflate at equivalent quality, and decompresses 2-14x faster at the fastest level. For HTTP payloads, log shipping, or binary serialization, that gap is significant.

Streaming Compression in Five Lines

The API mirrors BrotliStream and GZipStream, so the migration path is familiar:

using System.IO.Compression;

await using var input = File.OpenRead("dump.json");
await using var output = File.Create("dump.json.zst");
await using var zstd = new ZstandardStream(output, CompressionMode.Compress);

await input.CopyToAsync(zstd);

Decompression is the mirror image: wrap the input stream and read.

await using var compressed = File.OpenRead("dump.json.zst");
await using var zstd = new ZstandardStream(compressed, CompressionMode.Decompress);
await using var output = File.Create("dump.json");

await zstd.CopyToAsync(output);

Fine-Grained Control with ZstandardEncoder

When you need to set compression levels or use trained dictionaries, drop down to ZstandardEncoder:

using var encoder = new ZstandardEncoder(compressionLevel: 6);

Span<byte> source = GetPayload();
Span<byte> destination = new byte[ZstandardEncoder.GetMaxCompressedLength(source.Length)];

encoder.TryCompress(source, destination, out int bytesWritten);

Compression levels range from 1 (fastest) to 22 (smallest output). Level 3, the default, already beats Deflate ratios for most workloads. ZstandardDictionary lets you train on representative samples for even better ratios on small, repetitive payloads like API responses or log lines.

HttpClient Gets Automatic Zstd Decompression

DecompressionMethods now includes a Zstandard member, so opting in to transparent HTTP decompression is one flag:

var handler = new HttpClientHandler
{
    AutomaticDecompression = DecompressionMethods.Zstandard
};
var client = new HttpClient(handler);

If the server sends a Content-Encoding: zstd response, the handler decompresses it before your code ever sees the stream.

What to Try Now

Install the .NET 11 Preview SDK, target net11.0, and swap one of your existing BrotliStream or GZipStream call sites to ZstandardStream. Measure throughput and compressed size: the numbers tend to speak for themselves.

The full API surface, including ZstandardCompressionOptions for window size tuning, is documented on Microsoft Learn.