diff --git a/CHANGELOG.md b/CHANGELOG.md
index bab3e63099a..010b162e2f9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,8 @@ We refer to [GitHub issues](https://github.com/JabRef/jabref/issues) by using `#
 - We changed the default keyboard shortcuts for moving between entries when the entry editor is active to ̀<kbd>alt</kbd> + <kbd>up/down</kbd>.
 - Opening a new file now prompts the directory of the currently selected file, instead of the directory of the last opened file.
 - Window state is saved on close and restored on start.
+- We made the MathSciNet fetcher more reliable.
+- We added the ISBN fetcher to the list of fetcher available under "Update with bibliographic information from the web" in the entry editor toolbar.
 - Files without a defined external file type are now directly opened with the default application of the operating system
 - We streamlined the process to rename and move files by removing the confirmation dialogs.
 - We removed the redundant new lines of markings and wrapped the summary in the File annotation tab. [#3823](https://github.com/JabRef/jabref/issues/3823)
diff --git a/src/main/java/org/jabref/logic/importer/WebFetchers.java b/src/main/java/org/jabref/logic/importer/WebFetchers.java
index 3329a6215f2..c06849201f3 100644
--- a/src/main/java/org/jabref/logic/importer/WebFetchers.java
+++ b/src/main/java/org/jabref/logic/importer/WebFetchers.java
@@ -119,6 +119,7 @@ public static List<EntryBasedFetcher> getEntryBasedFetchers(ImportFormatPreferen
         ArrayList<EntryBasedFetcher> list = new ArrayList<>();
         list.add(new AstrophysicsDataSystem(importFormatPreferences));
         list.add(new DoiFetcher(importFormatPreferences));
+        list.add(new IsbnFetcher(importFormatPreferences));
         list.add(new MathSciNet(importFormatPreferences));
         list.add(new CrossRef());
         list.sort(Comparator.comparing(WebFetcher::getName));
diff --git a/src/main/java/org/jabref/logic/importer/fetcher/IsbnFetcher.java b/src/main/java/org/jabref/logic/importer/fetcher/IsbnFetcher.java
index 343d5e3e8cd..80612f0af83 100644
--- a/src/main/java/org/jabref/logic/importer/fetcher/IsbnFetcher.java
+++ b/src/main/java/org/jabref/logic/importer/fetcher/IsbnFetcher.java
@@ -1,23 +1,32 @@
 package org.jabref.logic.importer.fetcher;
 
-import java.net.MalformedURLException;
-import java.net.URISyntaxException;
-import java.net.URL;
+import java.util.Collections;
+import java.util.List;
 import java.util.Optional;
 
+import org.jabref.logic.help.HelpFile;
+import org.jabref.logic.importer.EntryBasedFetcher;
 import org.jabref.logic.importer.FetcherException;
+import org.jabref.logic.importer.IdBasedFetcher;
 import org.jabref.logic.importer.ImportFormatPreferences;
 import org.jabref.model.entry.BibEntry;
+import org.jabref.model.entry.FieldName;
+import org.jabref.model.util.OptionalUtil;
 
 import org.jsoup.helper.StringUtil;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Fetcher for ISBN trying ebook.de first and then chimbori.com
  */
-public class IsbnFetcher extends AbstractIsbnFetcher {
+public class IsbnFetcher implements EntryBasedFetcher, IdBasedFetcher {
+
+    protected final ImportFormatPreferences importFormatPreferences;
+    Logger LOGGER = LoggerFactory.getLogger(IsbnFetcher.class);
 
     public IsbnFetcher(ImportFormatPreferences importFormatPreferences) {
-        super(importFormatPreferences);
+        this.importFormatPreferences = importFormatPreferences;
     }
 
     @Override
@@ -25,12 +34,9 @@ public String getName() {
         return "ISBN";
     }
 
-    /**
-     * Method never used
-     */
     @Override
-    public URL getURLForID(String identifier) throws URISyntaxException, MalformedURLException, FetcherException {
-        return null;
+    public Optional<HelpFile> getHelpPage() {
+        return Optional.of(HelpFile.FETCHER_ISBN);
     }
 
     @Override
@@ -39,8 +45,6 @@ public Optional<BibEntry> performSearchById(String identifier) throws FetcherExc
             return Optional.empty();
         }
 
-        this.ensureThatIsbnIsValid(identifier);
-
         IsbnViaEbookDeFetcher isbnViaEbookDeFetcher = new IsbnViaEbookDeFetcher(importFormatPreferences);
         Optional<BibEntry> bibEntry = isbnViaEbookDeFetcher.performSearchById(identifier);
         // nothing found at ebook.de, try chimbori.com
@@ -55,8 +59,12 @@ public Optional<BibEntry> performSearchById(String identifier) throws FetcherExc
     }
 
     @Override
-    public void doPostCleanup(BibEntry entry) {
-        // no action needed
+    public List<BibEntry> performSearch(BibEntry entry) throws FetcherException {
+        Optional<String> isbn = entry.getField(FieldName.ISBN);
+        if (isbn.isPresent()) {
+            return OptionalUtil.toList(performSearchById(isbn.get()));
+        } else {
+            return Collections.emptyList();
+        }
     }
-
 }
diff --git a/src/main/java/org/jabref/logic/importer/fetcher/MathSciNet.java b/src/main/java/org/jabref/logic/importer/fetcher/MathSciNet.java
index 603e84eac60..774d4155c00 100644
--- a/src/main/java/org/jabref/logic/importer/fetcher/MathSciNet.java
+++ b/src/main/java/org/jabref/logic/importer/fetcher/MathSciNet.java
@@ -8,6 +8,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
@@ -52,6 +53,12 @@ public String getName() {
      */
     @Override
     public URL getURLForEntry(BibEntry entry) throws URISyntaxException, MalformedURLException, FetcherException {
+        Optional<String> mrNumberInEntry = entry.getField(FieldName.MR_NUMBER);
+        if (mrNumberInEntry.isPresent()) {
+            // We are lucky and already know the id, so use it instead
+            return getURLForID(mrNumberInEntry.get());
+        }
+
         URIBuilder uriBuilder = new URIBuilder("https://mathscinet.ams.org/mrlookup");
         uriBuilder.addParameter("format", "bibtex");
 
diff --git a/src/test/java/org/jabref/logic/importer/fetcher/IsbnFetcherTest.java b/src/test/java/org/jabref/logic/importer/fetcher/IsbnFetcherTest.java
index ed140ff3dc8..bc39f08ebc1 100644
--- a/src/test/java/org/jabref/logic/importer/fetcher/IsbnFetcherTest.java
+++ b/src/test/java/org/jabref/logic/importer/fetcher/IsbnFetcherTest.java
@@ -1,5 +1,7 @@
 package org.jabref.logic.importer.fetcher;
 
+import java.util.Collections;
+import java.util.List;
 import java.util.Optional;
 
 import org.jabref.logic.importer.FetcherException;
@@ -18,13 +20,13 @@
 import static org.mockito.Mockito.mock;
 
 @FetcherTest
-public class IsbnFetcherTest {
+class IsbnFetcherTest {
 
     private IsbnFetcher fetcher;
     private BibEntry bibEntry;
 
     @BeforeEach
-    public void setUp() {
+    void setUp() {
         fetcher = new IsbnFetcher(mock(ImportFormatPreferences.class, Answers.RETURNS_DEEP_STUBS));
 
         bibEntry = new BibEntry();
@@ -41,54 +43,61 @@ public void setUp() {
     }
 
     @Test
-    public void testName() {
+    void testName() {
         assertEquals("ISBN", fetcher.getName());
     }
 
     @Test
-    public void testHelpPage() {
+    void testHelpPage() {
         assertEquals("ISBNtoBibTeX", fetcher.getHelpPage().get().getPageName());
     }
 
     @Test
-    public void searchByIdSuccessfulWithShortISBN() throws FetcherException {
+    void searchByIdSuccessfulWithShortISBN() throws FetcherException {
         Optional<BibEntry> fetchedEntry = fetcher.performSearchById("0134685997");
         assertEquals(Optional.of(bibEntry), fetchedEntry);
     }
 
     @Test
-    public void searchByIdSuccessfulWithLongISBN() throws FetcherException {
+    void searchByIdSuccessfulWithLongISBN() throws FetcherException {
         Optional<BibEntry> fetchedEntry = fetcher.performSearchById("9780134685991");
         assertEquals(Optional.of(bibEntry), fetchedEntry);
     }
 
     @Test
-    public void searchByIdReturnsEmptyWithEmptyISBN() throws FetcherException {
+    void searchByIdReturnsEmptyWithEmptyISBN() throws FetcherException {
         Optional<BibEntry> fetchedEntry = fetcher.performSearchById("");
         assertEquals(Optional.empty(), fetchedEntry);
     }
 
     @Test
-    public void searchByIdThrowsExceptionForShortInvalidISBN() {
+    void searchByIdThrowsExceptionForShortInvalidISBN() {
         assertThrows(FetcherException.class, () -> fetcher.performSearchById("123456789"));
     }
 
     @Test
-    public void searchByIdThrowsExceptionForLongInvalidISB() {
+    void searchByIdThrowsExceptionForLongInvalidISB() {
         assertThrows(FetcherException.class, () -> fetcher.performSearchById("012345678910"));
     }
 
     @Test
-    public void searchByIdThrowsExceptionForInvalidISBN() {
+    void searchByIdThrowsExceptionForInvalidISBN() {
         assertThrows(FetcherException.class, () -> fetcher.performSearchById("jabref-4-ever"));
     }
 
+    @Test
+    void searchByEntryWithISBNSuccessful() throws FetcherException {
+        BibEntry input = new BibEntry().withField("isbn", "0134685997");
+
+        List<BibEntry> fetchedEntry = fetcher.performSearch(input);
+        assertEquals(Collections.singletonList(bibEntry), fetchedEntry);
+    }
     /**
      * This test searches for a valid ISBN. See https://www.amazon.de/dp/3728128155/?tag=jabref-21 However, this ISBN is
      * not available on ebook.de. The fetcher should something as it falls back to Chimbori
      */
     @Test
-    public void searchForIsbnAvailableAtChimboriButNonOnEbookDe() throws FetcherException {
+    void searchForIsbnAvailableAtChimboriButNonOnEbookDe() throws FetcherException {
         Optional<BibEntry> fetchedEntry = fetcher.performSearchById("3728128155");
         assertNotEquals(Optional.empty(), fetchedEntry);
     }
diff --git a/src/test/java/org/jabref/logic/importer/fetcher/MathSciNetTest.java b/src/test/java/org/jabref/logic/importer/fetcher/MathSciNetTest.java
index e66d81f0948..cf938c036bb 100644
--- a/src/test/java/org/jabref/logic/importer/fetcher/MathSciNetTest.java
+++ b/src/test/java/org/jabref/logic/importer/fetcher/MathSciNetTest.java
@@ -1,5 +1,6 @@
 package org.jabref.logic.importer.fetcher;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 
@@ -55,8 +56,16 @@ void searchByEntryFindsEntry() throws Exception {
         searchEntry.setField("journal", "fluid");
 
         List<BibEntry> fetchedEntries = fetcher.performSearch(searchEntry);
-        assertFalse(fetchedEntries.isEmpty());
-        assertEquals(ratiuEntry, fetchedEntries.get(0));
+        assertEquals(Collections.singletonList(ratiuEntry), fetchedEntries);
+    }
+
+    @Test
+    void searchByIdInEntryFindsEntry() throws Exception {
+        BibEntry searchEntry = new BibEntry();
+        searchEntry.setField("mrnumber", "3537908");
+
+        List<BibEntry> fetchedEntries = fetcher.performSearch(searchEntry);
+        assertEquals(Collections.singletonList(ratiuEntry), fetchedEntries);
     }
 
     @Test