diff --git a/backend/src/modules/account/dto/update-profile.dto.ts b/backend/src/modules/account/dto/update-profile.dto.ts
index 4f08123..3f097a1 100644
--- a/backend/src/modules/account/dto/update-profile.dto.ts
+++ b/backend/src/modules/account/dto/update-profile.dto.ts
@@ -5,6 +5,7 @@ import {
   Matches,
   MaxLength,
 } from 'class-validator';
+import { Transform } from 'class-transformer';
 
 import {
   FACEBOOK_PROFILE_REGEX,
@@ -56,6 +57,11 @@ export class UpdateProfileDto {
   github?: string;
 
   @IsOptional()
+  // Leading/trailing whitespace (e.g. from a copy-paste) parses fine as a URL
+  // but fails @IsUrl(), which doesn't tolerate it — trim before validating.
+  @Transform(({ value }: { value: unknown }) =>
+    typeof value === 'string' ? value.trim() : value,
+  )
   @IsUrl()
   @MaxLength(500)
   portfolio?: string;
diff --git a/backend/src/modules/applications/dto/create-application.dto.ts b/backend/src/modules/applications/dto/create-application.dto.ts
index d481a13..a1f2955 100644
--- a/backend/src/modules/applications/dto/create-application.dto.ts
+++ b/backend/src/modules/applications/dto/create-application.dto.ts
@@ -13,7 +13,7 @@ import {
   ValidationArguments,
   ValidateNested,
 } from 'class-validator';
-import { Type } from 'class-transformer';
+import { Transform, Type } from 'class-transformer';
 
 import { APPLICATION_COUNTRY_CODES } from '@common/constants/countries';
 import {
@@ -130,6 +130,11 @@ export class CreateApplicationDto {
   github!: string;
 
   @IsOptional()
+  // Leading/trailing whitespace (e.g. from a copy-paste) parses fine as a URL
+  // but fails @IsUrl(), which doesn't tolerate it — trim before validating.
+  @Transform(({ value }: { value: unknown }) =>
+    typeof value === 'string' ? value.trim() : value,
+  )
   @IsUrl()
   @MaxLength(500)
   portfolio?: string;
diff --git a/backend/test/unit/modules/account/dto.spec.ts b/backend/test/unit/modules/account/dto.spec.ts
index 6b4e7c2..4ad97d8 100644
--- a/backend/test/unit/modules/account/dto.spec.ts
+++ b/backend/test/unit/modules/account/dto.spec.ts
@@ -41,6 +41,12 @@ describe('UpdateProfileDto', () => {
       'name',
     );
   });
+
+  it('accepts a portfolio URL with incidental surrounding whitespace', () => {
+    expect(
+      failingProps(UpdateProfileDto, { portfolio: '  https://ada.dev  ' }),
+    ).toEqual([]);
+  });
 });
 
 describe('UpdateWalletsDto', () => {
diff --git a/backend/test/unit/modules/applications/dto.spec.ts b/backend/test/unit/modules/applications/dto.spec.ts
index ae93a82..1f2cc3f 100644
--- a/backend/test/unit/modules/applications/dto.spec.ts
+++ b/backend/test/unit/modules/applications/dto.spec.ts
@@ -47,6 +47,18 @@ describe('CreateApplicationDto', () => {
     );
   });
 
+  it('accepts a portfolio URL with incidental surrounding whitespace', () => {
+    expect(
+      failingProps({ ...VALID, portfolio: '  https://ada.dev  ' }),
+    ).toEqual([]);
+  });
+
+  it('rejects a portfolio value that is not a URL once trimmed', () => {
+    expect(failingProps({ ...VALID, portfolio: '  not a url  ' })).toContain(
+      'portfolio',
+    );
+  });
+
   it('accepts a valid EVM wallet address', () => {
     expect(
       failingProps({
diff --git a/frontend/src/constants/shared/social-profiles.ts b/frontend/src/constants/shared/social-profiles.ts
index a4b61a1..8ef0e7d 100644
--- a/frontend/src/constants/shared/social-profiles.ts
+++ b/frontend/src/constants/shared/social-profiles.ts
@@ -47,9 +47,15 @@ export const SOCIAL_PROFILE_MESSAGES = {
 export const optionalMatching = (re: RegExp, message: string) =>
   z.string().refine((val) => !val || re.test(val), message);
 
-/** A string field that is allowed to be blank but, if filled, must be a URL. */
+/**
+ * A string field that is allowed to be blank but, if filled, must be a URL.
+ * Trims first: the WHATWG URL parser silently accepts leading/trailing
+ * whitespace (so untrimmed input still passes this check), but the backend's
+ * validator does not — trimming here keeps the value valid end-to-end.
+ */
 export const optionalUrl = z
   .string()
+  .trim()
   .refine(
     (val) => !val || z.string().url().safeParse(val).success,
     "Enter a valid URL (e.g. https://...)",
diff --git a/frontend/tests/constants/apply-form.test.ts b/frontend/tests/constants/apply-form.test.ts
index 719b19b..e37024c 100644
--- a/frontend/tests/constants/apply-form.test.ts
+++ b/frontend/tests/constants/apply-form.test.ts
@@ -82,6 +82,15 @@ describe("APPLICATION_FORM_SCHEMA", () => {
     });
     expect(result.success).toBe(true);
   });
+
+  it("accepts and trims a portfolio URL with surrounding whitespace", () => {
+    const result = APPLICATION_FORM_SCHEMA.safeParse({
+      ...VALID,
+      portfolio: "  https://ada.dev  ",
+    });
+    expect(result.success).toBe(true);
+    if (result.success) expect(result.data.portfolio).toBe("https://ada.dev");
+  });
 });
 
 describe("isApplicationStepSlug", () => {
diff --git a/frontend/tests/features/profile-form-schema.test.ts b/frontend/tests/features/profile-form-schema.test.ts
index 7c09c67..2f5ab9c 100644
--- a/frontend/tests/features/profile-form-schema.test.ts
+++ b/frontend/tests/features/profile-form-schema.test.ts
@@ -63,4 +63,13 @@ describe("PROFILE_FORM_SCHEMA", () => {
     });
     expect(result.success).toBe(false);
   });
+
+  it("accepts and trims a portfolio URL with surrounding whitespace", () => {
+    const result = PROFILE_FORM_SCHEMA.safeParse({
+      ...blank,
+      portfolio: "  https://ada.dev  ",
+    });
+    expect(result.success).toBe(true);
+    if (result.success) expect(result.data.portfolio).toBe("https://ada.dev");
+  });
 });