diff --git a/source/net/yacy/cora/document/id/MultiProtocolURL.java b/source/net/yacy/cora/document/id/MultiProtocolURL.java
index e9c1e00bf..e4b84bca5 100644
--- a/source/net/yacy/cora/document/id/MultiProtocolURL.java
+++ b/source/net/yacy/cora/document/id/MultiProtocolURL.java
@@ -216,7 +216,7 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
                 p = 4;
             }
         }
-        this.protocol = url.substring(0, p).toLowerCase().trim().intern();
+        this.protocol = url.substring(0, p).toLowerCase(Locale.ROOT).trim().intern();
         if (url.length() < p + 4) throw new MalformedURLException("URL not parseable: '" + url + "'");
         if (!this.protocol.equals("file") && url.substring(p + 1, p + 3).equals("//")) {
             // identify host, userInfo and file for http and ftp protocol
@@ -417,7 +417,7 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
             // a relative path that uses the protocol from the base url
             relPath = baseURL.protocol + ":" + relPath;
         }
-        if (relPath.toLowerCase().startsWith("javascript:")) {
+        if (relPath.toLowerCase(Locale.ROOT).startsWith("javascript:")) {
             this.path = baseURL.path;
         } else if (
                 isHTTP(relPath) ||
@@ -426,7 +426,7 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
                 isFile(relPath) ||
                 isSMB(relPath)) {
             this.path = baseURL.path;
-        } else if (relPath.contains(":") && patternMail.matcher(relPath.toLowerCase()).find()) { // discards also any unknown protocol from previous if
+        } else if (relPath.contains(":") && patternMail.matcher(relPath.toLowerCase(Locale.ROOT)).find()) { // discards also any unknown protocol from previous if
             throw new MalformedURLException("relative path malformed: " + relPath);
         } else if (relPath.length() > 0 && relPath.charAt(0) == '/') {
             this.path = relPath;
@@ -647,7 +647,7 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
                     sbuf.append("%25");      // '%' RFC 1738 2.2 unsafe char shall be encoded
                 }
             } else if (ch == '&') { 
-                if (i < len - 6 && "amp;".equals(s.substring(i + 1, i + 5).toLowerCase())) {
+                if (i < len - 6 && "amp;".equals(s.substring(i + 1, i + 5).toLowerCase(Locale.ROOT))) {
                     sbuf.append((char)ch);   // leave it that way, it is used the right way
                 } else {
                     sbuf.append("%26");    // this must be urlencoded
@@ -799,7 +799,7 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
         String q = this.searchpart;
         if (removeSessionID) {
             for (final String sid: sessionIDnames.keySet()) {
-                if (q.toLowerCase().startsWith(sid.toLowerCase() + "=")) {
+                if (q.toLowerCase(Locale.ROOT).startsWith(sid.toLowerCase(Locale.ROOT) + "=")) {
                     final int p = q.indexOf('&');
                     if (p < 0) {
                         if (excludeAnchor || this.anchor == null) return this.path;
@@ -812,7 +812,7 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
                     q = q.substring(p + 1);
                     continue;
                 }
-                final int p = q.toLowerCase().indexOf("&" + sid.toLowerCase() + "=",0);
+                final int p = q.toLowerCase(Locale.ROOT).indexOf("&" + sid.toLowerCase(Locale.ROOT) + "=",0);
                 if (p < 0) continue;
                 final int p1 = q.indexOf('&', p+1);
                 if (p1 < 0) {
@@ -852,14 +852,14 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
         if (p < 0) return "";
         final int q = fileName.lastIndexOf('?');
         if (q < 0) {
-            return fileName.substring(p + 1).toLowerCase();
+            return fileName.substring(p + 1).toLowerCase(Locale.ROOT);
         }
         // check last dot in query part
         if (p > q) {
             p = fileName.lastIndexOf('.', q);
             if (p < 0) return "";
         }
-        return fileName.substring(p + 1, q).toLowerCase();
+        return fileName.substring(p + 1, q).toLowerCase(Locale.ROOT);
     }
 
     /**
@@ -933,7 +933,7 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
     public InetAddress getInetAddress() {
         if (this.hostAddress != null) return this.hostAddress;
         if (this.host == null) return null; // this may happen for file:// urls
-        this.hostAddress = Domains.dnsResolve(this.host.toLowerCase());
+        this.hostAddress = Domains.dnsResolve(this.host.toLowerCase(Locale.ROOT));
         return this.hostAddress;
     }
 
@@ -1117,7 +1117,7 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
                 u.append(this.userInfo);
                 u.append("@");
             }
-            u.append(h.toLowerCase());
+            u.append(h.toLowerCase(Locale.ROOT));
         }
         if (!defaultPort) {
             u.append(":");
@@ -1165,7 +1165,7 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
                 u.append(this.userInfo);
                 u.append("@");
             }
-            u.append(h.toLowerCase());
+            u.append(h.toLowerCase(Locale.ROOT));
         }
         if (!defaultPort) {
             u.append(":");
@@ -1224,7 +1224,7 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
     }
 
     public static final boolean isCGI(final String extension) {
-        return extension != null && extension.length() > 0 && "cgi.exe".indexOf(extension.toLowerCase()) >= 0;
+        return extension != null && extension.length() > 0 && "cgi.exe".indexOf(extension.toLowerCase(Locale.ROOT)) >= 0;
     }
 
     /**
@@ -1232,14 +1232,14 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
      */
     @Deprecated
     public static final boolean isImage(final String extension) {
-        return extension != null && extension.length() > 0 && Response.docTypeExt(extension.toLowerCase()) == Response.DT_IMAGE;
+        return extension != null && extension.length() > 0 && Response.docTypeExt(extension.toLowerCase(Locale.ROOT)) == Response.DT_IMAGE;
     }
 
     public final boolean isIndividual() {
-        final String q = unescape(this.path.toLowerCase());
+        final String q = unescape(this.path.toLowerCase(Locale.ROOT));
         for (final String sid: sessionIDnames.keySet()) {
-            if (q.startsWith(sid.toLowerCase() + "=")) return true;
-            final int p = q.indexOf("&" + sid.toLowerCase() + "=",0);
+            if (q.startsWith(sid.toLowerCase(Locale.ROOT) + "=")) return true;
+            final int p = q.indexOf("&" + sid.toLowerCase(Locale.ROOT) + "=",0);
             if (p >= 0) return true;
         }
         int pos;
@@ -1273,7 +1273,7 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
         String language = "en";
         if (this.host == null) return language;
         final int pos = this.host.lastIndexOf('.');
-        String host_tld = this.host.substring(pos + 1).toLowerCase();
+        String host_tld = this.host.substring(pos + 1).toLowerCase(Locale.ROOT);
         if (pos == 0) return language;
         int length = this.host.length() - pos - 1;
         switch (length) {
@@ -2395,6 +2395,7 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
     public static String[] urlComps(String normalizedURL) {
         final int p = normalizedURL.indexOf("//",0);
         if (p > 0) normalizedURL = normalizedURL.substring(p + 2);
+        // TODO lowering case in a locale sensitive manner makes sense here, but the used language locale should not dependant on the default system locale
         return splitpattern.split(normalizedURL.toLowerCase()); // word components of the url
     }
     
diff --git a/test/java/net/yacy/cora/document/id/MultiProtocolURLTest.java b/test/java/net/yacy/cora/document/id/MultiProtocolURLTest.java
index 482ccc2c7..2e18ac578 100644
--- a/test/java/net/yacy/cora/document/id/MultiProtocolURLTest.java
+++ b/test/java/net/yacy/cora/document/id/MultiProtocolURLTest.java
@@ -14,10 +14,12 @@ import java.util.Map;
 import java.util.TreeSet;
 
 import org.junit.Test;
-//import junit.framework.TestCase;
 
+/**
+ * Automated unit tests for the {@link MultiProtocolURL} class.
+ */
 public class MultiProtocolURLTest {
-
+	
     @Test
     public void testSessionIdRemoval() throws MalformedURLException {
         String[][] testURIs = new String[][]{
@@ -169,11 +171,19 @@ public class MultiProtocolURLTest {
         Map<String, String> testurls = new HashMap<String, String>();
         // ( 1. parameter = urlstring to test, 2. parameter = expected protocol)
         testurls.put("http://host.com",  "http");
+        testurls.put("HTTP://EXAMPLE.COM",  "http");
+        testurls.put("https://host.com", "https");
         testurls.put("HTTPS://host.com", "https");
+        testurls.put("Ftp://example.org",   "ftp");
+        testurls.put("FTP://EXAMPLE.ORG",   "ftp");
         testurls.put("Ftp://host.com",   "ftp");
+        testurls.put("smb://host.com",   "smb");
         testurls.put("SMB://host.com",   "smb");
         testurls.put("/file.com",        "file");
         testurls.put("file://host.com/file.com", "file");
+        testurls.put("file:///file1.txt", "file");
+        testurls.put("FILE:///file2.txt", "file");
+        testurls.put("MAILTO:Abc@host.com",      "mailto");
         testurls.put("MailTo:Abc@host.com",      "mailto");
 
         for (String txt : testurls.keySet()) {
@@ -258,10 +268,12 @@ public class MultiProtocolURLTest {
         Map<String, String> testurls = new HashMap<String, String>();
         //  key=testurl, value=result
         testurls.put("path/file.xml","xml"); // easiest
+        testurls.put("/FILE.GIF","gif"); // easy upper case
         testurls.put("path/file?h.pdf",""); // file w/o extension
         testurls.put("file.html?param=h.pdf","html"); // dot in query part
         testurls.put("url?param=h.pdf",""); // dot in query part
         testurls.put("file.html?param", "html");
+        testurls.put("FILE.GIF?param", "gif");
         testurls.put("/path/","");
         for (String s : testurls.keySet()) {
             System.out.println("test getFileExtension: " + s + " -> " + testurls.get(s));