diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 93a9f57..da70ebb 100755
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -46,14 +46,35 @@ jobs:
         sudo cp brotli.ini /etc/php/${{ matrix.php-versions }}/mods-available/ &&
         sudo phpenmod -v ${{ matrix.php-versions }} brotli
 
+    - name: Add ZStandard extension (Ubuntu)
+      if: runner.os != 'Windows' && matrix.php-versions == '8.4'
+      run: >
+        git clone --recursive --depth=1 https://github.com/kjdev/php-ext-zstd.git &&
+        cd php-ext-zstd &&
+        phpize &&
+        ./configure --enable-zstd &&
+        make -j $(nproc) &&
+        echo "extension=zstd.so" > zstd.ini &&
+        sudo make install &&
+        sudo cp zstd.ini /etc/php/${{ matrix.php-versions }}/mods-available/ &&
+        sudo phpenmod -v ${{ matrix.php-versions }} zstd
+
     - name: Add Brotli extension (Windows)
       if: runner.os == 'Windows' && matrix.php-versions == '8.4'
       run: >
         curl -sSL -o brotli.zip https://github.com/kjdev/php-ext-brotli/releases/download/0.18.0/php_brotli-0.18.0-8.4-nts-vs17-x86_64.zip &&
         unzip brotli.zip &&
-        cp *.dll C:/tools/php/ext/php_brotli.dll &&
+        cp php_brotli*.dll C:/tools/php/ext/php_brotli.dll &&
         echo "extension=brotli" >> C:/tools/php/php.ini
 
+    - name: Add ZStandard extension (Windows)
+      if: runner.os == 'Windows' && matrix.php-versions == '8.4'
+      run: >
+        curl -sSL -o zstd.zip https://github.com/kjdev/php-ext-zstd/releases/download/0.15.0/php_zstd-0.15.0-8.4-nts-vs17-x86_64.zip &&
+        unzip zstd.zip &&
+        cp php_zstd*.dll C:/tools/php/ext/php_zstd.dll &&
+        echo "extension=zstd" >> C:/tools/php/php.ini
+
     - name: Validate composer.json and composer.lock
       run: composer validate
 
diff --git a/ChangeLog.md b/ChangeLog.md
index 554d751..b3a5943 100755
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -5,6 +5,8 @@ Compression streams ChangeLog
 
 ## 2.0.0 / ????-??-??
 
+* Merged PR #8: Add ZStandard compression, based on the `zstd` extension
+  from https://github.com/kjdev/php-ext-zstd/ - see issue #7.
 * **Heads up:** Dropped support for PHP < 7.4, see xp-framework/rfc#343
   (@thekid)
 * **Heads up:** Algorithm implementations must change their `compress`
diff --git a/README.md b/README.md
index 00abb51..8f4dafb 100755
--- a/README.md
+++ b/README.md
@@ -8,7 +8,7 @@ Compression streams
 [![Supports PHP 8.0+](https://raw.githubusercontent.com/xp-framework/web/master/static/php-8_0plus.svg)](http://php.net/)
 [![Latest Stable Version](https://poser.pugx.org/xp-forge/compression/version.svg)](https://packagist.org/packages/xp-forge/compression)
 
-Compressing output and decompressing input streams including GZip, BZip2 and Brotli.
+Compressing output and decompressing input streams including GZip, BZip2, ZStandard and Brotli.
 
 Examples
 --------
@@ -44,6 +44,7 @@ Compression algorithms are implemented in C and thus require a specific PHP exte
 * **GZip** - requires PHP's ["zlib" extension](https://www.php.net/zlib)
 * **Bzip2** - requires PHP's ["bzip2" extension](https://www.php.net/bzip2)
 * **Brotli** - requires https://github.com/kjdev/php-ext-brotli
+* **ZStandard** - requires https://github.com/kjdev/php-ext-zstd
 
 Accessing these algorithms can be done via the `Compression` API:
 
@@ -96,6 +97,7 @@ io.streams.compress.Algorithms@{
   io.streams.compress.Gzip(token: gzip, extension: .gz, supported: true, levels: 1..9)
   io.streams.compress.Bzip2(token: bzip2, extension: .bz2, supported: false, levels: 1..9)
   io.streams.compress.Brotli(token: br, extension: .br, supported: true, levels: 1..11)
+  io.streams.compress.ZStandard(token: zstd, extension: .zstd, supported: true, levels: 1..22)
 }
 ```
 
diff --git a/src/main/php/io/streams/Compression.class.php b/src/main/php/io/streams/Compression.class.php
index b1534d8..712dd10 100755
--- a/src/main/php/io/streams/Compression.class.php
+++ b/src/main/php/io/streams/Compression.class.php
@@ -1,6 +1,6 @@
 <?php namespace io\streams;
 
-use io\streams\compress\{Algorithm, Algorithms, None, Brotli, Bzip2, Gzip};
+use io\streams\compress\{Algorithm, Algorithms, None, Brotli, Bzip2, Gzip, ZStandard};
 use lang\MethodNotImplementedException;
 
 /**
@@ -22,7 +22,7 @@ static function __static() {
     self::$NONE= new None();
 
     // Register known algorithms included in this library
-    self::$algorithms= (new Algorithms())->add(new Gzip(), new Bzip2(), new Brotli());
+    self::$algorithms= (new Algorithms())->add(new Gzip(), new Bzip2(), new Brotli(), new ZStandard());
   }
 
   /**
diff --git a/src/main/php/io/streams/compress/Brotli.class.php b/src/main/php/io/streams/compress/Brotli.class.php
index f53350b..373a8ad 100755
--- a/src/main/php/io/streams/compress/Brotli.class.php
+++ b/src/main/php/io/streams/compress/Brotli.class.php
@@ -1,5 +1,6 @@
 <?php namespace io\streams\compress;
 
+use io\IOException;
 use io\streams\{InputStream, OutputStream, Compression};
 
 class Brotli extends Algorithm {
@@ -29,7 +30,12 @@ public function compress(string $data, $options= null): string {
 
   /** Decompresses bytes */
   public function decompress(string $bytes): string {
-    return brotli_uncompress($bytes);
+    if (false === ($data= brotli_uncompress($bytes))) {
+      $e= new IOException('Decompression failed');
+      \xp::gc(__FILE__);
+      throw $e;
+    }
+    return $data;
   }
 
   /** Opens an input stream for reading */
diff --git a/src/main/php/io/streams/compress/ZStandard.class.php b/src/main/php/io/streams/compress/ZStandard.class.php
new file mode 100755
index 0000000..8091795
--- /dev/null
+++ b/src/main/php/io/streams/compress/ZStandard.class.php
@@ -0,0 +1,50 @@
+<?php namespace io\streams\compress;
+
+use io\IOException;
+use io\streams\{InputStream, OutputStream, Compression};
+
+class ZStandard extends Algorithm {
+
+  /** Returns whether this algorithm is supported in the current setup */
+  public function supported(): bool { return extension_loaded('zstd'); }
+
+  /** Returns the algorithm's name */
+  public function name(): string { return 'zstandard'; }
+
+  /** Returns the algorithm's HTTP Content-Encoding token */
+  public function token(): string { return 'zstd'; }
+
+  /** Returns the algorithm's common file extension, including a leading "." */
+  public function extension(): string { return '.zstd'; }
+
+  /** Maps fastest, default and strongest levels */
+  public function level(int $select): int {
+    static $levels= [Compression::FASTEST => 1, Compression::DEFAULT => 3, Compression::STRONGEST => 22];
+    return $levels[$select] ?? $select;
+  }
+
+  /** Compresses data */
+  public function compress(string $data, $options= null): string {
+    return zstd_compress($data, $this->level(Options::from($options)->level));
+  }
+
+  /** Decompresses bytes */
+  public function decompress(string $bytes): string {
+    if (false === ($data= zstd_uncompress($bytes))) {
+      $e= new IOException('Decompression failed');
+      \xp::gc(__FILE__);
+      throw $e;
+    }
+    return $data;
+  }
+
+  /** Opens an input stream for reading */
+  public function open(InputStream $in): InputStream {
+    return new ZStandardInputStream($in);
+  }
+
+  /** Opens an output stream for writing */
+  public function create(OutputStream $out, $options= null): OutputStream {
+    return new ZStandardOutputStream($out, $this->level(Options::from($options)->level));
+  }
+}
\ No newline at end of file
diff --git a/src/main/php/io/streams/compress/ZStandardInputStream.class.php b/src/main/php/io/streams/compress/ZStandardInputStream.class.php
new file mode 100755
index 0000000..abe2429
--- /dev/null
+++ b/src/main/php/io/streams/compress/ZStandardInputStream.class.php
@@ -0,0 +1,70 @@
+<?php namespace io\streams\compress;
+
+use io\IOException;
+use io\streams\InputStream;
+
+/**
+ * ZStandard input stream
+ *
+ * @ext  zstd
+ * @test io.streams.compress.unittest.BrotliInputStreamTest
+ * @see  https://github.com/kjdev/php-ext-zstd
+ */
+class ZStandardInputStream implements InputStream {
+  private $in, $handle;
+
+  /**
+   * Creates a new compressing output stream
+   *
+   * @param  io.streams.InputStream $in The stream to read from
+   */
+  public function __construct(InputStream $in) {
+    $this->in= $in;
+    $this->handle= zstd_uncompress_init();
+  }
+
+  /**
+   * Read a string
+   *
+   * @param   int limit default 8192
+   * @return  string
+   */
+  public function read($limit= 8192) {
+    $bytes= zstd_uncompress_add($this->handle, $this->in->read($limit));
+    if (false === $bytes) {
+      $e= new IOException('Failed to uncompress');
+      \xp::gc(__FILE__);
+      throw $e;
+    }
+    return $bytes;
+  }
+
+  /**
+   * Returns the number of bytes that can be read from this stream 
+   * without blocking.
+   *
+   * @return int
+   */
+  public function available() {
+    return $this->in->available();
+  }
+
+  /**
+   * Close this buffer.
+   *
+   * @return void
+   */
+  public function close() {
+    if ($this->handle) {
+      $this->handle= null;
+      $this->in->close();
+    }
+  }
+  
+  /**
+   * Destructor. Ensures output stream is closed.
+   */
+  public function __destruct() {
+    $this->close();
+  }
+}
\ No newline at end of file
diff --git a/src/main/php/io/streams/compress/ZStandardOutputStream.class.php b/src/main/php/io/streams/compress/ZStandardOutputStream.class.php
new file mode 100755
index 0000000..2321ef1
--- /dev/null
+++ b/src/main/php/io/streams/compress/ZStandardOutputStream.class.php
@@ -0,0 +1,64 @@
+<?php namespace io\streams\compress;
+
+use io\streams\OutputStream;
+use lang\IllegalArgumentException;
+
+/**
+ * ZStandard output stream
+ *
+ * @ext  zstd
+ * @test io.streams.compress.unittest.ZStandardOutputStreamTest
+ * @see  https://github.com/kjdev/php-ext-zstd
+ */
+class ZStandardOutputStream implements OutputStream {
+  private $out, $handle;
+
+  /**
+   * Creates a new compressing output stream
+   *
+   * @param  io.streams.OutputStream $out The stream to write to
+   * @param  int $level
+   * @throws lang.IllegalArgumentException
+   */
+  public function __construct(OutputStream $out, $level= ZSTD_COMPRESS_LEVEL_DEFAULT) {
+    if ($level < ZSTD_COMPRESS_LEVEL_MIN || $level > ZSTD_COMPRESS_LEVEL_MAX) {
+      throw new IllegalArgumentException('Level must be between '.ZSTD_COMPRESS_LEVEL_MIN.' and '.ZSTD_COMPRESS_LEVEL_MAX);
+    }
+
+    $this->out= $out;
+    $this->handle= zstd_compress_init($level);
+  }
+
+  /**
+   * Write a string
+   *
+   * @param  var $arg
+   * @return void
+   */
+  public function write($arg) {
+    $this->out->write(zstd_compress_add($this->handle, $arg, false));
+  }
+
+  /**
+   * Flush this buffer
+   *
+   * @return void
+   */
+  public function flush() {
+    // NOOP
+  }
+
+  /**
+   * Closes this object. May be called more than once, which may
+   * not fail - that is, if the object is already closed, this 
+   * method should have no effect.
+   *
+   * @return void
+   */
+  public function close() {
+    if (null !== $this->handle) {
+      $this->out->write(zstd_compress_add($this->handle, '', true));
+      $this->handle= null;
+    }
+  }
+}
\ No newline at end of file
diff --git a/src/test/php/io/streams/compress/unittest/CompressionTest.class.php b/src/test/php/io/streams/compress/unittest/CompressionTest.class.php
index 10fc1e9..9445010 100755
--- a/src/test/php/io/streams/compress/unittest/CompressionTest.class.php
+++ b/src/test/php/io/streams/compress/unittest/CompressionTest.class.php
@@ -15,14 +15,17 @@ private function names() {
     yield ['gzip', 'gzip'];
     yield ['bzip2', 'bzip2'];
     yield ['brotli', 'brotli'];
+    yield ['zstandard', 'zstandard'];
 
     // File extensions
     yield ['.gz', 'gzip'];
     yield ['.bz2', 'bzip2'];
     yield ['.br', 'brotli'];
+    yield ['.zstd', 'zstandard'];
 
     // HTTP Content-Encoding aliases
     yield ['br', 'brotli'];    
+    yield ['zstd', 'zstandard'];
   }
 
   /** @return iterable */
@@ -46,6 +49,16 @@ private function erroneous() {
     if ($bzip2->supported()) {
       yield [$bzip2, "BZh61AY&SY\331<Plain data>"];
     }
+
+    $brotli= $algorithms->named('brotli');
+    if ($brotli->supported()) {
+      yield [$brotli, "<Plain data>"];
+    }
+
+    $zstandard= $algorithms->named('zstandard');
+    if ($zstandard->supported()) {
+      yield [$zstandard, "<Plain data>"];
+    }
   }
 
   #[Test]
@@ -54,7 +67,7 @@ public function enumerating_included_algorithms() {
     foreach (Compression::algorithms() as $name => $algorithm) {
       $names[]= $name;
     }
-    Assert::equals(['gzip', 'bzip2', 'brotli'], $names);
+    Assert::equals(['gzip', 'bzip2', 'brotli', 'zstandard'], $names);
   }
 
   #[Test]
@@ -77,17 +90,17 @@ public function algorithms_named($name, $expected) {
     Assert::equals($expected, Compression::algorithms()->named($name)->name());
   }
 
-  #[Test, Values([['gzip', 'zlib'], ['bzip2', 'bz2'], ['brotli', 'brotli']])]
+  #[Test, Values([['gzip', 'zlib'], ['bzip2', 'bz2'], ['brotli', 'brotli'], ['zstandard', 'zstd']])]
   public function supported($compression, $extension) {
     Assert::equals(extension_loaded($extension), Compression::algorithms()->named($compression)->supported());
   }
 
-  #[Test, Values([['gzip', 'gzip'], ['bzip2', 'bzip2'], ['brotli', 'br']])]
+  #[Test, Values([['gzip', 'gzip'], ['bzip2', 'bzip2'], ['brotli', 'br'], ['zstandard', 'zstd']])]
   public function token($compression, $expected) {
     Assert::equals($expected, Compression::algorithms()->named($compression)->token());
   }
 
-  #[Test, Values([['gzip', '.gz'], ['bzip2', '.bz2'], ['brotli', '.br']])]
+  #[Test, Values([['gzip', '.gz'], ['bzip2', '.bz2'], ['brotli', '.br'], ['zstandard', '.zstd']])]
   public function extension($compression, $expected) {
     Assert::equals($expected, Compression::algorithms()->named($compression)->extension());
   }
diff --git a/src/test/php/io/streams/compress/unittest/ZStandardInputStreamTest.class.php b/src/test/php/io/streams/compress/unittest/ZStandardInputStreamTest.class.php
new file mode 100755
index 0000000..bd8870c
--- /dev/null
+++ b/src/test/php/io/streams/compress/unittest/ZStandardInputStreamTest.class.php
@@ -0,0 +1,59 @@
+<?php namespace io\streams\compress\unittest;
+
+use io\IOException;
+use io\streams\MemoryInputStream;
+use io\streams\compress\ZStandardInputStream;
+use test\verify\Runtime;
+use test\{Assert, Test, Values};
+
+#[Runtime(extensions: ['zstd'])]
+class ZStandardInputStreamTest {
+
+  /** @return iterable */
+  private function compressable() {
+    foreach ([ZSTD_COMPRESS_LEVEL_MIN, ZSTD_COMPRESS_LEVEL_DEFAULT, ZSTD_COMPRESS_LEVEL_MAX] as $level) {
+      yield [$level, ''];
+      yield [$level, 'Test'];
+      yield [$level, "GIF89a\x14\x12\x77..."];
+    }
+  }
+
+  #[Test]
+  public function can_create() {
+    new ZStandardInputStream(new MemoryInputStream(''));
+  }
+
+  #[Test]
+  public function read_plain() {
+    $in= new ZStandardInputStream(new MemoryInputStream('Test'));
+    Assert::throws(IOException::class, function() use($in) {
+      $in->read();
+    });
+    $in->close();
+  }
+
+  #[Test, Values(from: 'compressable')]
+  public function read_compressed($level, $bytes) {
+    $in= new ZStandardInputStream(new MemoryInputStream(zstd_compress($bytes, $level)));
+    $read= $in->read();
+    $rest= $in->available();
+    $in->close();
+
+    Assert::equals($bytes, $read);
+    Assert::equals(0, $rest);
+  }
+
+  #[Test, Values([1, 8192, 16384])]
+  public function read_all($length) {
+    $bytes= random_bytes($length);
+    $in= new ZStandardInputStream(new MemoryInputStream(zstd_compress($bytes)));
+
+    $read= '';
+    while ($in->available()) {
+      $read.= $in->read();
+    }
+    $in->close();
+
+    Assert::equals($bytes, $read);
+  }
+}
\ No newline at end of file
diff --git a/src/test/php/io/streams/compress/unittest/ZStandardOutputStreamTest.class.php b/src/test/php/io/streams/compress/unittest/ZStandardOutputStreamTest.class.php
new file mode 100755
index 0000000..523878a
--- /dev/null
+++ b/src/test/php/io/streams/compress/unittest/ZStandardOutputStreamTest.class.php
@@ -0,0 +1,34 @@
+<?php namespace io\streams\compress\unittest;
+
+use io\streams\MemoryOutputStream;
+use io\streams\compress\ZStandardOutputStream;
+use lang\IllegalArgumentException;
+use test\verify\Runtime;
+use test\{Assert, Expect, Test, Values};
+
+#[Runtime(extensions: ['zstd'])]
+class ZStandardOutputStreamTest {
+
+  #[Test]
+  public function can_create() {
+    new ZStandardOutputStream(new MemoryOutputStream());
+  }
+
+  #[Test, Expect(IllegalArgumentException::class)]
+  public function using_invalid_compression_level() {
+    new ZStandardOutputStream(new MemoryOutputStream(), -1);
+  }
+
+  #[Test, Values([1, 3, 22])]
+  public function write($level) {
+    $out= new MemoryOutputStream();
+
+    $fixture= new ZStandardOutputStream($out, $level);
+    $fixture->write('Hello');
+    $fixture->write(' ');
+    $fixture->write('World');
+    $fixture->close();
+
+    Assert::equals('Hello World', zstd_uncompress($out->bytes()));
+  }
+}
\ No newline at end of file