diff --git a/gradle/changelog/unicode_name_validation.yaml b/gradle/changelog/unicode_name_validation.yaml
new file mode 100644
index 0000000000..d495a14c2b
--- /dev/null
+++ b/gradle/changelog/unicode_name_validation.yaml
@@ -0,0 +1,2 @@
+- type: changed
+  description: Allow all UTF-8 characters except URL identifiers as user and group names and for namespaces. ([#1600](https://github.com/scm-manager/scm-manager/pull/1600))
diff --git a/scm-core/src/main/java/sonia/scm/repository/Repository.java b/scm-core/src/main/java/sonia/scm/repository/Repository.java
index fce742f4fa..5382d28a75 100644
--- a/scm-core/src/main/java/sonia/scm/repository/Repository.java
+++ b/scm-core/src/main/java/sonia/scm/repository/Repository.java
@@ -243,7 +243,7 @@ public class Repository extends BasicPropertiesAware implements ModelObject, Per
    */
   @Override
   public boolean isValid() {
-    return ValidationUtil.isRepositoryNameValid(namespace)
+    return ValidationUtil.isNameValid(namespace)
       && ValidationUtil.isRepositoryNameValid(name)
       && Util.isNotEmpty(type)
       && ((Util.isEmpty(contact)) || ValidationUtil.isMailAddressValid(contact));
diff --git a/scm-core/src/main/java/sonia/scm/repository/spi/HttpScmProtocol.java b/scm-core/src/main/java/sonia/scm/repository/spi/HttpScmProtocol.java
index e3cd03a8cd..6693f29f52 100644
--- a/scm-core/src/main/java/sonia/scm/repository/spi/HttpScmProtocol.java
+++ b/scm-core/src/main/java/sonia/scm/repository/spi/HttpScmProtocol.java
@@ -21,11 +21,12 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
-    
+
 package sonia.scm.repository.spi;
 
 import sonia.scm.repository.Repository;
 import sonia.scm.repository.api.ScmProtocol;
+import sonia.scm.util.HttpUtil;
 
 import javax.servlet.ServletConfig;
 import javax.servlet.ServletException;
@@ -51,7 +52,7 @@ public abstract class HttpScmProtocol implements ScmProtocol {
 
   @Override
   public String getUrl() {
-      return URI.create(basePath + "/").resolve(String.format("repo/%s/%s", repository.getNamespace(), repository.getName())).toASCIIString();
+    return URI.create(basePath + "/").resolve(String.format("repo/%s/%s", HttpUtil.encode(repository.getNamespace()), HttpUtil.encode(repository.getName()))).toASCIIString();
   }
 
   public final void serve(HttpServletRequest request, HttpServletResponse response, ServletConfig config) throws ServletException, IOException {
diff --git a/scm-core/src/main/java/sonia/scm/util/ValidationUtil.java b/scm-core/src/main/java/sonia/scm/util/ValidationUtil.java
index 730a08c545..a06572c885 100644
--- a/scm-core/src/main/java/sonia/scm/util/ValidationUtil.java
+++ b/scm-core/src/main/java/sonia/scm/util/ValidationUtil.java
@@ -21,106 +21,69 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
-    
-package sonia.scm.util;
 
-//~--- non-JDK imports --------------------------------------------------------
+package sonia.scm.util;
 
 import sonia.scm.Validateable;
 
 import java.util.regex.Pattern;
 
-//~--- JDK imports ------------------------------------------------------------
+public final class ValidationUtil {
 
-/**
- *
- * @author Sebastian Sdorra
- */
-public final class ValidationUtil
-{
+  private static final String REGEX_MAIL = "^[A-Za-z0-9][\\w.-]*@[A-Za-z0-9][\\w\\-\\.]*\\.[A-Za-z0-9][A-Za-z0-9-]+$";
 
-  /** Field description */
-  private static final String REGEX_MAIL =
-    "^[A-Za-z0-9][\\w.-]*@[A-Za-z0-9][\\w\\-\\.]*\\.[A-Za-z0-9][A-Za-z0-9-]+$";
-
-  /** Field description */
-  public static final String REGEX_NAME =
-    "^[A-Za-z0-9\\.\\-_][A-Za-z0-9\\.\\-_@]*$";
+  public static final String REGEX_NAME = "^(?:(?:[^:/?#;&=\\s@%\\\\][^:/?#;&=%\\\\]*[^:/?#;&=\\s%\\\\])|(?:[^:/?#;&=\\s@%\\\\]))$";
 
   public static final String REGEX_REPOSITORYNAME = "(?!^\\.\\.$)(?!^\\.$)(?!.*[\\\\\\[\\]])(?!.*[.]git$)^[A-Za-z0-9\\.][A-Za-z0-9\\.\\-_]*$";
 
-  /** Field description */
   private static final Pattern PATTERN_REPOSITORYNAME = Pattern.compile(REGEX_REPOSITORYNAME);
 
-  //~--- constructors ---------------------------------------------------------
-
-  /**
-   * Constructs ...
-   *
-   */
-  private ValidationUtil() {}
-
-  //~--- get methods ----------------------------------------------------------
-
-  /**
-   *  Method description
-   *
-   *
-   *  @param value
-   *
-   *  @return
-   */
-  public static boolean isFilenameValid(String value)
-  {
-    return Util.isNotEmpty(value) && isNotContaining(value, "/", "\\", ":");
+  private ValidationUtil() {
   }
 
   /**
-   * Method description
+   * Returns {@code true} if the filename is valid.
    *
-   *
-   * @param value
-   *
-   * @return
+   * @param filename filename to be validated
+   * @return {@code true} if filename is valid
    */
-  public static boolean isMailAddressValid(String value)
-  {
-    return Util.isNotEmpty(value) && value.matches(REGEX_MAIL);
+  public static boolean isFilenameValid(String filename) {
+    return Util.isNotEmpty(filename) && isNotContaining(filename, "/", "\\", ":");
   }
 
   /**
-   * Method description
+   * Returns {@code true} if the mail is valid.
    *
-   *
-   * @param name
-   *
-   * @return
+   * @param mail email-address to be validated
+   * @return {@code true} if mail is valid
    */
-  public static boolean isNameValid(String name)
-  {
-    return Util.isNotEmpty(name) && name.matches(REGEX_NAME);
+  public static boolean isMailAddressValid(String mail) {
+    return Util.isNotEmpty(mail) && mail.matches(REGEX_MAIL);
   }
 
   /**
-   * Method description
+   * Returns {@code true} if the name is valid.
    *
-   *
-   * @param value
-   * @param notAllowedStrings
-   *
-   * @return
+   * @param name name to be validated
+   * @return {@code true} if name is valid
    */
-  public static boolean isNotContaining(String value,
-    String... notAllowedStrings)
-  {
+  public static boolean isNameValid(String name) {
+    return Util.isNotEmpty(name) && name.matches(REGEX_NAME) && !name.equals("..");
+  }
+
+  /**
+   * Returns {@code true} if the object is valid.
+   *
+   * @param value             value to be checked
+   * @param notAllowedStrings one or more strings which should not be included in value
+   * @return {@code true} if string has no not allowed strings else false
+   */
+  public static boolean isNotContaining(String value, String... notAllowedStrings) {
     boolean result = Util.isNotEmpty(value);
 
-    if (result && (notAllowedStrings != null))
-    {
-      for (String nas : notAllowedStrings)
-      {
-        if (value.indexOf(nas) >= 0)
-        {
+    if (result && (notAllowedStrings != null)) {
+      for (String nas : notAllowedStrings) {
+        if (value.contains(nas)) {
           result = false;
 
           break;
@@ -135,24 +98,20 @@ public final class ValidationUtil
    * Returns {@code true} if the repository name is valid.
    *
    * @param name repository name
-   * @since 1.9
-   *
    * @return {@code true} if repository name is valid
+   * @since 1.9
    */
   public static boolean isRepositoryNameValid(String name) {
     return PATTERN_REPOSITORYNAME.matcher(name).matches();
   }
 
   /**
-   * Method description
+   * Returns {@code true} if the object is valid.
    *
-   *
-   * @param validateable
-   *
-   * @return
+   * @param validatable object to be validated
+   * @return {@code true} if object is valid
    */
-  public static boolean isValid(Validateable validateable)
-  {
-    return (validateable != null) && validateable.isValid();
+  public static boolean isValid(Validateable validatable) {
+    return (validatable != null) && validatable.isValid();
   }
 }
diff --git a/scm-core/src/test/java/sonia/scm/repository/spi/HttpScmProtocolTest.java b/scm-core/src/test/java/sonia/scm/repository/spi/HttpScmProtocolTest.java
index 4b6d94b670..57609b4785 100644
--- a/scm-core/src/test/java/sonia/scm/repository/spi/HttpScmProtocolTest.java
+++ b/scm-core/src/test/java/sonia/scm/repository/spi/HttpScmProtocolTest.java
@@ -21,10 +21,13 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
-    
+
 package sonia.scm.repository.spi;
 
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DynamicTest;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestFactory;
 import sonia.scm.repository.Repository;
 
@@ -37,16 +40,44 @@ import static org.assertj.core.api.Assertions.assertThat;
 
 class HttpScmProtocolTest {
 
-  @TestFactory
-  Stream<DynamicTest> shouldCreateCorrectUrlsWithContextPath() {
-    return Stream.of("http://localhost/scm", "http://localhost/scm/")
-      .map(url -> assertResultingUrl(url, "http://localhost/scm/repo/space/name"));
+  private String namespace;
+  private String name;
+
+  @Nested
+  class WithSimpleNamespaceAndName {
+
+    @BeforeEach
+    void setNamespaceAndName() {
+      namespace = "space";
+      name = "name";
+    }
+
+    @TestFactory
+    Stream<DynamicTest> shouldCreateCorrectUrlsWithContextPath() {
+      return Stream.of("http://localhost/scm", "http://localhost/scm/")
+        .map(url -> assertResultingUrl(url, "http://localhost/scm/repo/space/name"));
+    }
+
+    @TestFactory
+    Stream<DynamicTest> shouldCreateCorrectUrlsWithPort() {
+      return Stream.of("http://localhost:8080", "http://localhost:8080/")
+        .map(url -> assertResultingUrl(url, "http://localhost:8080/repo/space/name"));
+    }
   }
 
-  @TestFactory
-  Stream<DynamicTest> shouldCreateCorrectUrlsWithPort() {
-    return Stream.of("http://localhost:8080", "http://localhost:8080/")
-      .map(url -> assertResultingUrl(url, "http://localhost:8080/repo/space/name"));
+  @Nested
+  class WithComplexNamespaceAndName{
+
+    @BeforeEach
+    void setNamespaceAndName() {
+      namespace = "name space";
+      name = "name";
+    }
+
+    @Test
+    void shouldCreateCorrectUrlsWithContextPath() {
+      assertResultingUrl("http://localhost/scm", "http://localhost/scm/repo/name%20space/name");
+    }
   }
 
   DynamicTest assertResultingUrl(String baseUrl, String expectedUrl) {
@@ -55,7 +86,7 @@ class HttpScmProtocolTest {
   }
 
   private HttpScmProtocol createInstanceOfHttpScmProtocol(String baseUrl) {
-    return new HttpScmProtocol(new Repository("", "", "space", "name"), baseUrl) {
+    return new HttpScmProtocol(new Repository("", "", namespace, name), baseUrl) {
       @Override
       protected void serve(HttpServletRequest request, HttpServletResponse response, Repository repository, ServletConfig config) {
       }
diff --git a/scm-core/src/test/java/sonia/scm/util/ValidationUtilTest.java b/scm-core/src/test/java/sonia/scm/util/ValidationUtilTest.java
index a5f81a7150..e430ae334b 100644
--- a/scm-core/src/test/java/sonia/scm/util/ValidationUtilTest.java
+++ b/scm-core/src/test/java/sonia/scm/util/ValidationUtilTest.java
@@ -21,108 +21,119 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
-    
+
 package sonia.scm.util;
 
-//~--- non-JDK imports --------------------------------------------------------
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
-import org.junit.Test;
-
-import static org.junit.Assert.*;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 /**
- *
  * @author Sebastian Sdorra
  */
-public class ValidationUtilTest
-{
+class ValidationUtilTest {
 
-  /**
-   * Method description
-   *
-   */
-  @Test
-  public void testIsFilenameValid()
-  {
-
-    // true
-    assertTrue(ValidationUtil.isFilenameValid("test"));
-    assertTrue(ValidationUtil.isFilenameValid("test 123"));
-
-    // false
-    assertFalse(ValidationUtil.isFilenameValid("../../"));
-    assertFalse(ValidationUtil.isFilenameValid("test/../.."));
-    assertFalse(ValidationUtil.isFilenameValid("\\ka"));
-    assertFalse(ValidationUtil.isFilenameValid("ka:on"));
+  @ParameterizedTest
+  @ValueSource(strings = {
+    "test",
+    "test 123"
+  })
+  void shouldAcceptFilename(String value) {
+    assertTrue(ValidationUtil.isFilenameValid(value));
   }
 
-  /**
-   * Method description
-   *
-   */
-  @Test
-  public void testIsMailAddressValid()
-  {
-
-    // true
-    assertTrue(ValidationUtil.isMailAddressValid("s.sdorra@ostfalia.de"));
-    assertTrue(ValidationUtil.isMailAddressValid("sdorra@ostfalia.de"));
-    assertTrue(ValidationUtil.isMailAddressValid("s.sdorra@hbk-bs.de"));
-    assertTrue(ValidationUtil.isMailAddressValid("s.sdorra@gmail.com"));
-    assertTrue(ValidationUtil.isMailAddressValid("s.sdorra@t.co"));
-    assertTrue(ValidationUtil.isMailAddressValid("s.sdorra@ucla.college")); 
-    assertTrue(ValidationUtil.isMailAddressValid("s.sdorra@example.xn--p1ai"));
-    
-    // issue 909
-    assertTrue(ValidationUtil.isMailAddressValid("s.sdorra@scm.solutions")); 
-
-    // false
-    assertFalse(ValidationUtil.isMailAddressValid("ostfalia.de"));
-    assertFalse(ValidationUtil.isMailAddressValid("@ostfalia.de"));
-    assertFalse(ValidationUtil.isMailAddressValid("s.sdorra@"));
-    assertFalse(ValidationUtil.isMailAddressValid("s.sdorra@ostfalia"));
-    assertFalse(ValidationUtil.isMailAddressValid("s.sdorra@@ostfalia.de"));
-    assertFalse(ValidationUtil.isMailAddressValid("s.sdorra@ ostfalia.de"));
-    assertFalse(ValidationUtil.isMailAddressValid("s.sdorra @ostfalia.de"));
+  @ParameterizedTest
+  @ValueSource(strings = {
+    "../../",
+    "test/../..",
+    "\\ka, \"ka:on\""
+  })
+  void shouldRejectFilename(String value) {
+    assertFalse(ValidationUtil.isFilenameValid(value));
   }
 
-  /**
-   * Method description
-   *
-   */
-  @Test
-  public void testIsNameValid()
-  {
-
-    // true
-    assertTrue(ValidationUtil.isNameValid("test"));
-    assertTrue(ValidationUtil.isNameValid("test.git"));
-    assertTrue(ValidationUtil.isNameValid("Test123.git"));
-    assertTrue(ValidationUtil.isNameValid("Test123-git"));
-    assertTrue(ValidationUtil.isNameValid("Test_user-123.git"));
-    assertTrue(ValidationUtil.isNameValid("test@scm-manager.de"));
-    assertTrue(ValidationUtil.isNameValid("t"));
-
-    // false
-    assertFalse(ValidationUtil.isNameValid("test 123"));
-    assertFalse(ValidationUtil.isNameValid(" test 123"));
-    assertFalse(ValidationUtil.isNameValid(" test 123 "));
-    assertFalse(ValidationUtil.isNameValid("test 123 "));
-    assertFalse(ValidationUtil.isNameValid("test/123"));
-    assertFalse(ValidationUtil.isNameValid("test%123"));
-    assertFalse(ValidationUtil.isNameValid("test:123"));
-    assertFalse(ValidationUtil.isNameValid("t "));
-    assertFalse(ValidationUtil.isNameValid(" t"));
-    assertFalse(ValidationUtil.isNameValid(" t "));
+  @ParameterizedTest
+  @ValueSource(strings = {
+    "s.sdorra@ostfalia.de",
+    "sdorra@ostfalia.de",
+    "s.sdorra@hbk-bs.de",
+    "s.sdorra@gmail.com",
+    "s.sdorra@t.co",
+    "s.sdorra@ucla.college",
+    "s.sdorra@example.xn--p1ai",
+    "s.sdorra@scm.solutions" // issue 909
+  })
+  void shouldAcceptMailAddress(String value) {
+    assertTrue(ValidationUtil.isMailAddressValid(value));
+  }
+
+  @ParameterizedTest
+  @ValueSource(strings = {
+    "ostfalia.de",
+    "@ostfalia.de",
+    "s.sdorra@",
+    "s.sdorra@ostfalia",
+    "s.sdorra@@ostfalia.de",
+    "s.sdorra@ ostfalia.de",
+    "s.sdorra @ostfalia.de"
+  })
+  void shouldRejectMailAddress(String value) {
+    assertFalse(ValidationUtil.isMailAddressValid(value));
+  }
+
+  @ParameterizedTest
+  @ValueSource(strings = {
+    "test",
+    "test.git",
+    "Test123.git",
+    "Test123-git",
+    "Test_user-123.git",
+    "test@scm-manager.de",
+    "t",
+    "Лорем-ипсум",
+    "Λορεμ.ιπσθμ",
+    "լոռեմիպսում",
+    "ლორემიფსუმ",
+    "प्रमान",
+    "詳性約",
+    "隠サレニ",
+    "법률",
+    "المدن",
+    "אחד",
+    "Hu-rëm"
+  })
+  void shouldAcceptName(String value) {
+    assertTrue(ValidationUtil.isNameValid(value));
+  }
+
+  @ParameterizedTest
+  @ValueSource(strings = {
+    "@",
+    "@test",
+    " test123",
+    "test/123",
+    "test:123",
+    "test#123",
+    "test%123",
+    "test&123",
+    "test?123",
+    "test=123",
+    "test;123",
+    "@test123",
+    "t ",
+    " t",
+    " t ",
+    ".."
+  })
+  void shouldRejectName(String value) {
+    assertFalse(ValidationUtil.isNameValid(value));
   }
 
-  /**
-   * Method description
-   *
-   */
   @Test
-  public void testIsNotContaining()
-  {
+  void testIsNotContaining() {
 
     // true
     assertTrue(ValidationUtil.isNotContaining("test", "abc"));
@@ -134,9 +145,8 @@ public class ValidationUtilTest
     assertFalse(ValidationUtil.isNotContaining("test", "t"));
   }
 
-  @Test
-  public void testIsRepositoryNameValid() {
-    String[] validPaths = {
+  @ParameterizedTest
+  @ValueSource(strings = {
       "scm",
       "scm-",
       "scm_",
@@ -150,69 +160,66 @@ public class ValidationUtilTest
       "..c",
       "d..",
       "a..c"
-    };
+  })
+  void shouldAcceptRepositoryName(String path) {
+    assertTrue(ValidationUtil.isRepositoryNameValid(path));
+  }
 
-    // issue 142, 144 and 148
-    String[] invalidPaths = {
-      ".",
-      "/",
-      "//",
-      "..",
-      "/.",
-      "/..",
-      "./",
-      "../",
-      "/../",
-      "/./",
-      "/...",
-      "/abc",
-      ".../",
-      "/sdf/",
-      "asdf/",
-      "./b",
-      "scm/plugins/.",
-      "scm/../plugins",
-      "scm/main/",
-      "/scm/main/",
-      "scm/./main",
-      "scm//main",
-      "scm\\main",
-      "scm/main-$HOME",
-      "scm/main-${HOME}-home",
-      "scm/main-%HOME-home",
-      "scm/main-%HOME%-home",
-      "abc$abc",
-      "abc%abc",
-      "abc<abc",
-      "abc>abc",
-      "abc#abc",
-      "abc+abc",
-      "abc{abc",
-      "abc}abc",
-      "abc(abc",
-      "abc)abc",
-      "abc[abc",
-      "abc]abc",
-      "abc|abc",
-      "scm/main",
-      "scm/plugins/git-plugin",
-      ".scm/plugins",
-      "a/b..",
-      "a/..b",
-      "scm/main",
-      "scm/plugins/git-plugin",
-      "_scm",
-      "-scm",
-      "scm.git",
-      "scm.git.git"
-    };
-
-    for (String path : validPaths) {
-      assertTrue(ValidationUtil.isRepositoryNameValid(path));
-    }
-
-    for (String path : invalidPaths) {
-      assertFalse(ValidationUtil.isRepositoryNameValid(path));
-    }
+  @ParameterizedTest
+  @ValueSource(strings = {
+    ".",
+    "/",
+    "//",
+    "..",
+    "/.",
+    "/..",
+    "./",
+    "../",
+    "/../",
+    "/./",
+    "/...",
+    "/abc",
+    ".../",
+    "/sdf/",
+    "asdf/",
+    "./b",
+    "scm/plugins/.",
+    "scm/../plugins",
+    "scm/main/",
+    "/scm/main/",
+    "scm/./main",
+    "scm//main",
+    "scm\\main",
+    "scm/main-$HOME",
+    "scm/main-${HOME}-home",
+    "scm/main-%HOME-home",
+    "scm/main-%HOME%-home",
+    "abc$abc",
+    "abc%abc",
+    "abc<abc",
+    "abc>abc",
+    "abc#abc",
+    "abc+abc",
+    "abc{abc",
+    "abc}abc",
+    "abc(abc",
+    "abc)abc",
+    "abc[abc",
+    "abc]abc",
+    "abc|abc",
+    "scm/main",
+    "scm/plugins/git-plugin",
+    ".scm/plugins",
+    "a/b..",
+    "a/..b",
+    "scm/main",
+    "scm/plugins/git-plugin",
+    "_scm",
+    "-scm",
+    "scm.git",
+    "scm.git.git"
+  })
+  void shouldRejectRepositoryName(String path) {
+    assertFalse(ValidationUtil.isRepositoryNameValid(path));
   }
 }
diff --git a/scm-core/src/test/java/sonia/scm/util/ValidationUtil_IllegalCharactersTest.java b/scm-core/src/test/java/sonia/scm/util/ValidationUtil_IllegalCharactersTest.java
deleted file mode 100644
index a36e157e7b..0000000000
--- a/scm-core/src/test/java/sonia/scm/util/ValidationUtil_IllegalCharactersTest.java
+++ /dev/null
@@ -1,71 +0,0 @@
-/*
- * MIT License
- *
- * Copyright (c) 2020-present Cloudogu GmbH and Contributors
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- */
-    
-package sonia.scm.util;
-
-import org.junit.Test;
-import org.junit.runner.RunWith;
-import org.junit.runners.Parameterized;
-
-import java.util.Collection;
-import java.util.List;
-import java.util.regex.Pattern;
-import java.util.stream.Collectors;
-import java.util.stream.IntStream;
-import java.util.stream.Stream;
-
-import static java.util.Arrays.asList;
-import static org.junit.Assert.assertFalse;
-import static sonia.scm.util.ValidationUtil.REGEX_NAME;
-
-@RunWith(Parameterized.class)
-public class ValidationUtil_IllegalCharactersTest {
-
-  private static final List<Character> ACCEPTED_CHARS = asList('@', '_', '-', '.');
-
-  private final Pattern userGroupPattern=Pattern.compile(REGEX_NAME);
-
-  private final String expression;
-
-  public ValidationUtil_IllegalCharactersTest(String expression) {
-    this.expression = expression;
-  }
-
-  @Parameterized.Parameters(name = "{0}")
-  public static Collection<String[]> createParameters() {
-    return Stream.concat(IntStream.range(0x20, 0x2f).mapToObj(i -> (char) i),    // chars before '0'
-           Stream.concat(IntStream.range(0x3a, 0x40).mapToObj(i -> (char) i),    // chars between '9' and 'A'
-           Stream.concat(IntStream.range(0x5b, 0x60).mapToObj(i -> (char) i),    // chars between 'Z' and 'a'
-                         IntStream.range(0x7b, 0xff).mapToObj(i -> (char) i))))  // chars after 'z'
-      .filter(c -> !ACCEPTED_CHARS.contains(c))
-      .flatMap(c -> Stream.of("abc" + c + "xyz", "@" + c, c + "tail"))
-      .map(c -> new String[] {c})
-      .collect(Collectors.toList());
-  }
-
-  @Test
-  public void shouldNotAcceptSpecialCharacters() {
-    assertFalse(userGroupPattern.matcher(expression).matches());
-  }
-}
diff --git a/scm-ui/ui-components/src/__snapshots__/storyshots.test.ts.snap b/scm-ui/ui-components/src/__snapshots__/storyshots.test.ts.snap
index 699095fe05..1452832896 100644
--- a/scm-ui/ui-components/src/__snapshots__/storyshots.test.ts.snap
+++ b/scm-ui/ui-components/src/__snapshots__/storyshots.test.ts.snap
@@ -46426,7 +46426,6 @@ exports[`Storyshots Forms|AddKeyValueEntryToTableField Default 1`] = `
           value=""
         />
       </div>
-      
     </div>
     <div
       className="field AddKeyValueEntryToTableField__StyledInputField-kiarql-1 hwPPZB"
@@ -46450,7 +46449,6 @@ exports[`Storyshots Forms|AddKeyValueEntryToTableField Default 1`] = `
           value=""
         />
       </div>
-      
     </div>
     <button
       className="button is-default AddKeyValueEntryToTableField__MarginTopButton-kiarql-2 hyqVki"
@@ -46504,7 +46502,6 @@ exports[`Storyshots Forms|AddKeyValueEntryToTableField Disabled 1`] = `
           value=""
         />
       </div>
-      
     </div>
     <div
       className="field AddKeyValueEntryToTableField__StyledInputField-kiarql-1 hwPPZB"
@@ -46529,7 +46526,6 @@ exports[`Storyshots Forms|AddKeyValueEntryToTableField Disabled 1`] = `
           value=""
         />
       </div>
-      
     </div>
     <button
       className="button is-default AddKeyValueEntryToTableField__MarginTopButton-kiarql-2 hyqVki"
diff --git a/scm-ui/ui-components/src/forms/InputField.tsx b/scm-ui/ui-components/src/forms/InputField.tsx
index 9f05656d16..bd2f3d176b 100644
--- a/scm-ui/ui-components/src/forms/InputField.tsx
+++ b/scm-ui/ui-components/src/forms/InputField.tsx
@@ -37,6 +37,7 @@ type Props = {
   onReturnPressed?: () => void;
   validationError?: boolean;
   errorMessage?: string;
+  informationMessage?: string;
   disabled?: boolean;
   helpText?: string;
   className?: string;
@@ -86,6 +87,7 @@ class InputField extends React.Component<Props> {
       value,
       validationError,
       errorMessage,
+      informationMessage,
       disabled,
       label,
       helpText,
@@ -93,7 +95,12 @@ class InputField extends React.Component<Props> {
       testId
     } = this.props;
     const errorView = validationError ? "is-danger" : "";
-    const helper = validationError ? <p className="help is-danger">{errorMessage}</p> : "";
+    let helper;
+    if (validationError) {
+      helper = <p className="help is-danger">{errorMessage}</p>;
+    } else if (informationMessage) {
+      helper = <p className="help is-info">{informationMessage}</p>;
+    }
     return (
       <div className={classNames("field", className)}>
         <LabelWithHelpIcon label={label} helpText={helpText} />
diff --git a/scm-ui/ui-components/src/markdown/remarkChangesetShortLinkParser.ts b/scm-ui/ui-components/src/markdown/remarkChangesetShortLinkParser.ts
index 6ed4d78411..96ba33f305 100644
--- a/scm-ui/ui-components/src/markdown/remarkChangesetShortLinkParser.ts
+++ b/scm-ui/ui-components/src/markdown/remarkChangesetShortLinkParser.ts
@@ -27,7 +27,7 @@ import { TFunction } from "i18next";
 import { AstPlugin } from "./PluginApi";
 import { Node, Parent } from "unist";
 
-const namePartRegex = nameRegex.source.substring(1, nameRegex.source.length - 1);
+const namePartRegex = nameRegex.source.substring(1, nameRegex.source.length - 1).replace(/\[\^([^\]s]+)\]/, "[^$1\\s]");
 
 export const regExpPattern = `(${namePartRegex})\\/(${namePartRegex})@([\\w\\d]+)`;
 
diff --git a/scm-ui/ui-components/src/validation.test.ts b/scm-ui/ui-components/src/validation.test.ts
index a1ca93b4f8..5d5537aaf4 100644
--- a/scm-ui/ui-components/src/validation.test.ts
+++ b/scm-ui/ui-components/src/validation.test.ts
@@ -32,16 +32,15 @@ describe("test name validation", () => {
     " test 123 ",
     "test 123 ",
     "test/123",
-    "test%123",
     "test:123",
     "t ",
     " t",
     " t ",
     "",
     " invalid_name",
-    "another%one",
-    "!!!",
-    "!_!"
+    "%",
+    "test%name",
+    "test\\name"
   ];
   for (const name of invalidNames) {
     it(`should return false for '${name}'`, () => {
@@ -52,6 +51,7 @@ describe("test name validation", () => {
   // valid names taken from ValidationUtilTest.java
   const validNames = [
     "test",
+    "test git",
     "test.git",
     "Test123.git",
     "Test123-git",
@@ -64,7 +64,18 @@ describe("test name validation", () => {
     "another1",
     "stillValid",
     "this.one_as-well",
-    "and@this"
+    "and@this",
+    "Лорем-ипсум",
+    "Λορεμ.ιπσθμ",
+    "լոռեմիպսում",
+    "ლორემიფსუმ",
+    "प्रमान",
+    "詳性約",
+    "隠サレニ",
+    "법률",
+    "المدن",
+    "אחד",
+    "Hu-rëm"
   ];
   for (const name of validNames) {
     it(`should return true for '${name}'`, () => {
diff --git a/scm-ui/ui-components/src/validation.ts b/scm-ui/ui-components/src/validation.ts
index ac3d953343..2ea710c03a 100644
--- a/scm-ui/ui-components/src/validation.ts
+++ b/scm-ui/ui-components/src/validation.ts
@@ -22,7 +22,7 @@
  * SOFTWARE.
  */
 
-export const nameRegex = /^[A-Za-z0-9\.\-_][A-Za-z0-9\.\-_@]*$/;
+export const nameRegex = /^(?:(?:[^:/?#;&=\s@%\\][^:/?#;&=%\\]*[^:/?#;&=\s%\\]+)|[^:/?#;&=\s@%\\])$/;
 
 export const isNameValid = (name: string) => {
   return nameRegex.test(name);
diff --git a/scm-ui/ui-webapp/public/locales/de/repos.json b/scm-ui/ui-webapp/public/locales/de/repos.json
index bd9e7bac41..2a7c5f5d6c 100644
--- a/scm-ui/ui-webapp/public/locales/de/repos.json
+++ b/scm-ui/ui-webapp/public/locales/de/repos.json
@@ -12,6 +12,7 @@
   },
   "validation": {
     "namespace-invalid": "Der Namespace des Repository ist ungültig",
+    "namespaceSpaceWarningText": "Achtung: Leerzeichen in Namespaces funktionieren prinzipiell, können jedoch bei einigen Funktionen zu Problemen führen",
     "name-invalid": "Der Name des Repository ist ungültig",
     "contact-invalid": "Der Kontakt muss eine gültige E-Mail Adresse sein",
     "url-invalid": "Die URL ist ungültig",
diff --git a/scm-ui/ui-webapp/public/locales/en/repos.json b/scm-ui/ui-webapp/public/locales/en/repos.json
index 7b34ffcdd1..b8635d9385 100644
--- a/scm-ui/ui-webapp/public/locales/en/repos.json
+++ b/scm-ui/ui-webapp/public/locales/en/repos.json
@@ -12,6 +12,7 @@
   },
   "validation": {
     "namespace-invalid": "The repository namespace is invalid",
+    "namespaceSpaceWarningText": "Warning: Spaces in namespaces will work in principle, but can lead to problems in some features",
     "name-invalid": "The repository name is invalid",
     "contact-invalid": "Contact must be a valid mail address",
     "url-invalid": "The URL is invalid",
diff --git a/scm-ui/ui-webapp/src/repos/components/NamespaceAndNameFields.tsx b/scm-ui/ui-webapp/src/repos/components/NamespaceAndNameFields.tsx
index dcd00bbb7d..85f2d93848 100644
--- a/scm-ui/ui-webapp/src/repos/components/NamespaceAndNameFields.tsx
+++ b/scm-ui/ui-webapp/src/repos/components/NamespaceAndNameFields.tsx
@@ -83,6 +83,11 @@ const NamespaceAndNameFields: FC<Props> = ({ repository, onChange, setValid, dis
   };
 
   const renderNamespaceField = () => {
+      let informationMessage = undefined;
+      if (repository?.namespace?.indexOf(" ") > 0) {
+        informationMessage =  t("validation.namespaceSpaceWarningText");
+      }
+
     const props = {
       label: t("repository.namespace"),
       helpText: t("help.namespaceHelpText"),
@@ -90,7 +95,8 @@ const NamespaceAndNameFields: FC<Props> = ({ repository, onChange, setValid, dis
       onChange: handleNamespaceChange,
       errorMessage: t("validation.namespace-invalid"),
       validationError: namespaceValidationError,
-      disabled: disabled
+      disabled: disabled,
+      informationMessage
     };
 
     if (namespaceStrategy === CUSTOM_NAMESPACE_STRATEGY) {
diff --git a/scm-ui/ui-webapp/src/repos/components/form/repositoryValidation.ts b/scm-ui/ui-webapp/src/repos/components/form/repositoryValidation.ts
index ce7bdb74fd..e4252a8a9b 100644
--- a/scm-ui/ui-webapp/src/repos/components/form/repositoryValidation.ts
+++ b/scm-ui/ui-webapp/src/repos/components/form/repositoryValidation.ts
@@ -23,12 +23,13 @@
  */
 
 import { validation } from "@scm-manager/ui-components";
+import { isNameValid as isUserNameValid } from "../../../users/components/userValidation";
 
 const nameRegex = /(?!^\.\.$)(?!^\.$)(?!.*[.]git$)(?!.*[\\\[\]])^[A-Za-z0-9\.][A-Za-z0-9\.\-_]*$/;
 const namespaceExceptionsRegex = /^(([0-9]{1,3})|(create)|(import))$/;
 
 export const isNamespaceValid = (name: string) => {
-  return nameRegex.test(name) && !namespaceExceptionsRegex.test(name);
+  return isUserNameValid(name) && !namespaceExceptionsRegex.test(name);
 };
 
 export const isNameValid = (name: string) => {
diff --git a/scm-webapp/src/main/java/sonia/scm/repository/CustomNamespaceStrategy.java b/scm-webapp/src/main/java/sonia/scm/repository/CustomNamespaceStrategy.java
index bc28e7104f..d0cdbdb9ae 100644
--- a/scm-webapp/src/main/java/sonia/scm/repository/CustomNamespaceStrategy.java
+++ b/scm-webapp/src/main/java/sonia/scm/repository/CustomNamespaceStrategy.java
@@ -43,9 +43,12 @@ public class CustomNamespaceStrategy implements NamespaceStrategy {
     doThrow()
       .violation("invalid namespace", "namespace")
       .when(
-        !ValidationUtil.isRepositoryNameValid(namespace)
+        !ValidationUtil.isNameValid(namespace)
           || ONE_TO_THREE_DIGITS.matcher(namespace).matches()
-          || namespace.equals("create"));
+          || namespace.equals("create")
+          || namespace.equals("import")
+          || namespace.equals("..")
+      );
 
     return namespace;
   }
diff --git a/scm-webapp/src/main/java/sonia/scm/repository/UsernameNamespaceStrategy.java b/scm-webapp/src/main/java/sonia/scm/repository/UsernameNamespaceStrategy.java
index 9b6cfd21c5..f323c8b9d5 100644
--- a/scm-webapp/src/main/java/sonia/scm/repository/UsernameNamespaceStrategy.java
+++ b/scm-webapp/src/main/java/sonia/scm/repository/UsernameNamespaceStrategy.java
@@ -21,7 +21,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
-    
+
 package sonia.scm.repository;
 
 import org.apache.shiro.SecurityUtils;
@@ -32,6 +32,6 @@ public class UsernameNamespaceStrategy implements NamespaceStrategy {
 
   @Override
   public String createNamespace(Repository repository) {
-    return SecurityUtils.getSubject().getPrincipal().toString();
+    return SecurityUtils.getSubject().getPrincipal().toString().replaceAll("\\s", "_");
   }
 }
diff --git a/scm-webapp/src/test/java/sonia/scm/api/v2/resources/GroupRootResourceTest.java b/scm-webapp/src/test/java/sonia/scm/api/v2/resources/GroupRootResourceTest.java
index 96e01c7318..7e2b96d937 100644
--- a/scm-webapp/src/test/java/sonia/scm/api/v2/resources/GroupRootResourceTest.java
+++ b/scm-webapp/src/test/java/sonia/scm/api/v2/resources/GroupRootResourceTest.java
@@ -76,7 +76,7 @@ public class GroupRootResourceTest {
   @Rule
   public ShiroRule shiro = new ShiroRule();
 
-  private RestDispatcher dispatcher = new RestDispatcher();
+  private final RestDispatcher dispatcher = new RestDispatcher();
 
   private final ResourceLinks resourceLinks = ResourceLinksMock.createMock(URI.create("/"));
 
@@ -284,27 +284,6 @@ public class GroupRootResourceTest {
 
     assertEquals(400, response.getStatus());
 
-    // the characters {[ are not allowed
-    groupJson = "{ \"name\": \"grp{name}\", \"type\": \"admin\" }";
-    request = MockHttpRequest
-      .post("/" + GroupRootResource.GROUPS_PATH_V2)
-      .contentType(VndMediaType.GROUP)
-      .content(groupJson.getBytes());
-
-    dispatcher.invoke(request, response);
-
-    assertEquals(400, response.getStatus());
-
-    groupJson = "{ \"name\": \"grp[name]\", \"type\": \"admin\" }";
-    request = MockHttpRequest
-      .post("/" + GroupRootResource.GROUPS_PATH_V2)
-      .contentType(VndMediaType.GROUP)
-      .content(groupJson.getBytes());
-
-    dispatcher.invoke(request, response);
-
-    assertEquals(400, response.getStatus());
-
     groupJson = "{ \"name\": \"grp/name\", \"type\": \"admin\" }";
     request = MockHttpRequest
       .post("/" + GroupRootResource.GROUPS_PATH_V2)
diff --git a/scm-webapp/src/test/java/sonia/scm/repository/UsernameNamespaceStrategyTest.java b/scm-webapp/src/test/java/sonia/scm/repository/UsernameNamespaceStrategyTest.java
index 846acc340c..4d471a1fb1 100644
--- a/scm-webapp/src/test/java/sonia/scm/repository/UsernameNamespaceStrategyTest.java
+++ b/scm-webapp/src/test/java/sonia/scm/repository/UsernameNamespaceStrategyTest.java
@@ -21,7 +21,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
-    
+
 package sonia.scm.repository;
 
 
@@ -63,4 +63,11 @@ class UsernameNamespaceStrategyTest {
     assertThat(namespace).isEqualTo("trillian");
   }
 
+  @Test
+  void shouldReplaceSpacesInPrincipalName() {
+    when(subject.getPrincipal()).thenReturn("arthur dent");
+
+    String namespace = usernameNamespaceStrategy.createNamespace(RepositoryTestData.createHeartOfGold());
+    assertThat(namespace).isEqualTo("arthur_dent");
+  }
 }