diff --git a/src/main/java/eu/crushedpixel/replaymod/gui/online/GuiRegister.java b/src/main/java/eu/crushedpixel/replaymod/gui/online/GuiRegister.java
index 0e465e19..203364c8 100644
--- a/src/main/java/eu/crushedpixel/replaymod/gui/online/GuiRegister.java
+++ b/src/main/java/eu/crushedpixel/replaymod/gui/online/GuiRegister.java
@@ -10,6 +10,7 @@ import de.johni0702.minecraft.gui.layout.VerticalLayout;
 import eu.crushedpixel.replaymod.api.ApiException;
 import eu.crushedpixel.replaymod.online.authentication.AuthenticationHandler;
 import eu.crushedpixel.replaymod.utils.EmailAddressUtils;
+import eu.crushedpixel.replaymod.utils.RegexUtils;
 import org.lwjgl.util.ReadableColor;
 
 public class GuiRegister extends AbstractGuiScreen<GuiRegister> {
@@ -101,6 +102,8 @@ public class GuiRegister extends AbstractGuiScreen<GuiRegister> {
                 String status = null;
                 if (usernameInput.getText().length() < 5) {
                     status = "replaymod.gui.register.error.shortusername";
+                } else if(!RegexUtils.isValid(RegexUtils.ALPHANUMERIC_UNDERSCORE, usernameInput.getText().trim())) {
+                    status = "replaymod.gui.register.error.invalidname";
                 } else if (passwordInput.getText().length() < 5) {
                     status = "replaymod.gui.register.error.shortpw";
                 } else if (!EmailAddressUtils.isValidEmailAddress(mailInput.getText())) {
diff --git a/src/main/java/eu/crushedpixel/replaymod/gui/online/GuiUploadFile.java b/src/main/java/eu/crushedpixel/replaymod/gui/online/GuiUploadFile.java
index b5ed34b6..b9298085 100755
--- a/src/main/java/eu/crushedpixel/replaymod/gui/online/GuiUploadFile.java
+++ b/src/main/java/eu/crushedpixel/replaymod/gui/online/GuiUploadFile.java
@@ -11,10 +11,7 @@ import eu.crushedpixel.replaymod.online.authentication.AuthenticationHandler;
 import eu.crushedpixel.replaymod.recording.ReplayMetaData;
 import eu.crushedpixel.replaymod.registry.KeybindRegistry;
 import eu.crushedpixel.replaymod.registry.ResourceHelper;
-import eu.crushedpixel.replaymod.utils.ImageUtils;
-import eu.crushedpixel.replaymod.utils.MouseUtils;
-import eu.crushedpixel.replaymod.utils.ReplayFile;
-import eu.crushedpixel.replaymod.utils.ReplayFileIO;
+import eu.crushedpixel.replaymod.utils.*;
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.gui.Gui;
 import net.minecraft.client.gui.GuiButton;
@@ -43,15 +40,11 @@ import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.concurrent.Callable;
-import java.util.regex.Pattern;
 
 public class GuiUploadFile extends GuiScreen implements ProgressUpdateListener {
 
     private final Minecraft mc = Minecraft.getMinecraft();
 
-    private static final Pattern titlePattern = Pattern.compile("[^a-z0-9 \\-_]", Pattern.CASE_INSENSITIVE);
-    private static final Pattern tagsPattern = Pattern.compile("[^a-z0-9,]", Pattern.CASE_INSENSITIVE);
-
     private final ResourceLocation textureResource;
     private DynamicTexture dynTex = null;
 
@@ -419,10 +412,11 @@ public class GuiUploadFile extends GuiScreen implements ProgressUpdateListener {
         boolean enabled = true;
         if(name.getText().trim().length() < 5 || name.getText().trim().length() > 30) {
             enabled = false;
-        } else if(titlePattern.matcher(name.getText()).find()) {
+            name.setTextColor(Color.RED.getRGB());
+        } else if(!RegexUtils.isValid(RegexUtils.ALPHANUMERIC_SPACE_HYPHEN_UNDERSCORE, name.getText())) {
             enabled = false;
             name.setTextColor(Color.RED.getRGB());
-        } else if(tagsPattern.matcher(tags.getText()).find()) {
+        } else if(!RegexUtils.isValid(RegexUtils.ALPHANUMERIC_COMMA, tags.getText())) {
             enabled = false;
             tags.setTextColor(Color.RED.getRGB());
         } else {
diff --git a/src/main/resources/assets/replaymod/lang/en_US.lang b/src/main/resources/assets/replaymod/lang/en_US.lang
index b86b140b..dc225cd4 100644
--- a/src/main/resources/assets/replaymod/lang/en_US.lang
+++ b/src/main/resources/assets/replaymod/lang/en_US.lang
@@ -129,6 +129,7 @@ replaymod.gui.register.confirmpw=Confirm Password
 
 replaymod.gui.register.error.nomatch=Passwords don't match
 replaymod.gui.register.error.shortusername=Username has to be at least 5 characters long
+replaymod.gui.register.error.invalidname=Username may only contain letters and numbers
 replaymod.gui.register.error.shortpw=Password has to be at least 5 characters long
 replaymod.gui.register.error.authfailed=Could not authenticate your Minecraft account