diff --git a/assets/src/bundles/webapp/webapp-utils.js b/assets/src/bundles/webapp/webapp-utils.js
--- a/assets/src/bundles/webapp/webapp-utils.js
+++ b/assets/src/bundles/webapp/webapp-utils.js
@@ -1,5 +1,5 @@
 /**
- * Copyright (C) 2018-2020  The Software Heritage developers
+ * Copyright (C) 2018-2021  The Software Heritage developers
  * See the AUTHORS file at the top-level directory of this distribution
  * License: GNU Affero General Public License version 3, or any later version
  * See top-level LICENSE file for more information
@@ -53,6 +53,33 @@
   $('body').css('padding-bottom', $('footer').outerHeight() + 'px');
 }
 
+function fixSearchInputMalformedSWHID(searchInputElt) {
+  const searchQueryText = $(searchInputElt).val().trim();
+  if (!searchQueryText.startsWith('swh:')) {
+    return;
+  }
+  const swhidWithQualifiers = searchQueryText.indexOf(';') !== -1;
+  if (swhidWithQualifiers) {
+    const lastQualifier = searchQueryText.split(';').pop();
+    if (lastQualifier === undefined) {
+      return;
+    }
+    const splittedQualifier = lastQualifier.split('=');
+    if (splittedQualifier.length !== 2) {
+      return;
+    }
+    const [qualifierName, qualifierValue] = splittedQualifier;
+    let fixedSWHIDFormat = searchQueryText;
+    if ((new Set(['anchor', 'lines', 'visit']).has(qualifierName) && qualifierValue.endsWith('/')) ||
+          (new Set(['origin', 'path']).has(qualifierName) && qualifierValue.endsWith('//'))) {
+      fixedSWHIDFormat = fixedSWHIDFormat.slice(0, -1);
+    }
+    if (fixedSWHIDFormat !== searchQueryText) {
+      $(searchInputElt).val(fixedSWHIDFormat);
+    }
+  }
+}
+
 $(document).ready(() => {
   // redirect to last browse page if any when clicking on the 'Browse' entry
   // in the sidebar
@@ -176,6 +203,12 @@
     window.location = `${Urls.browse_search()}?${queryParameters.toString()}`;
   });
 
+  // handle possible malformed input SWHID in search box after copy paste
+  // https://forge.softwareheritage.org/T3234
+  $('#swh-origins-url-patterns,#swh-origins-search-top-input').change(event => {
+    fixSearchInputMalformedSWHID(event.target);
+  });
+
 });
 
 export function initPage(page) {
diff --git a/cypress/integration/origin-search.spec.js b/cypress/integration/origin-search.spec.js
--- a/cypress/integration/origin-search.spec.js
+++ b/cypress/integration/origin-search.spec.js
@@ -500,4 +500,28 @@
     });
   });
 
+  context('Test fixable malformed SWHIDs', function() {
+
+    function checkMalformedSWHIDgetsFixed(url, searchInputElt, repoData) {
+      const malformedSWHIDs = [`swh:1:cnt:${repoData.content[0].sha1git};lines=45-60/`,
+                               `swh:1:cnt:${repoData.content[0].sha1git};origin=https://example.org/project//`];
+      for (let malformedSWHID of malformedSWHIDs) {
+        cy.visit(url);
+        cy.get(searchInputElt)
+          .type(malformedSWHID);
+        // to trigger input change event
+        cy.get('body').click();
+        cy.get(searchInputElt)
+          .should('have.value', malformedSWHID.slice(0, -1));
+      }
+    }
+
+    it('should remove invalid trailing slash when copying a malformed SWHID in search page input', function() {
+      checkMalformedSWHIDgetsFixed(this.Urls.browse_search(), '#swh-origins-url-patterns', this.unarchivedRepo);
+    });
+
+    it('should remove invalid trailing slash when copying a malformed SWHID in top right search input', function() {
+      checkMalformedSWHIDgetsFixed(this.Urls.browse_help(), '#swh-origins-search-top-input', this.unarchivedRepo);
+    });
+  });
 });