diff --git a/client/src/app/shared/forms/form-validators/user-validators.service.ts b/client/src/app/shared/forms/form-validators/user-validators.service.ts
index 1fd1cdf68ed3..967583cd218d 100644
--- a/client/src/app/shared/forms/form-validators/user-validators.service.ts
+++ b/client/src/app/shared/forms/form-validators/user-validators.service.ts
@@ -23,15 +23,15 @@ export class UserValidatorsService {
     this.USER_USERNAME = {
       VALIDATORS: [
         Validators.required,
-        Validators.minLength(3),
-        Validators.maxLength(20),
-        Validators.pattern(/^[a-z0-9._]+$/)
+        Validators.minLength(1),
+        Validators.maxLength(50),
+        Validators.pattern(/^[a-zA-Z0-9][a-zA-Z0-9-._]*$/)
       ],
       MESSAGES: {
         'required': this.i18n('Username is required.'),
-        'minlength': this.i18n('Username must be at least 3 characters long.'),
-        'maxlength': this.i18n('Username cannot be more than 20 characters long.'),
-        'pattern': this.i18n('Username should be only lowercase alphanumeric characters.')
+        'minlength': this.i18n('Username must be at least 1 character long.'),
+        'maxlength': this.i18n('Username cannot be more than 50 characters long.'),
+        'pattern': this.i18n('Username should start with a letter or number; dots, dashes and underscores are allowed.')
       }
     }
 
@@ -88,13 +88,13 @@ export class UserValidatorsService {
     this.USER_DISPLAY_NAME = {
       VALIDATORS: [
         Validators.required,
-        Validators.minLength(3),
-        Validators.maxLength(120)
+        Validators.minLength(1),
+        Validators.maxLength(50)
       ],
       MESSAGES: {
         'required': this.i18n('Display name is required.'),
-        'minlength': this.i18n('Display name must be at least 3 characters long.'),
-        'maxlength': this.i18n('Display name cannot be more than 120 characters long.')
+        'minlength': this.i18n('Display name must be at least 1 characters long.'),
+        'maxlength': this.i18n('Display name cannot be more than 50 characters long.')
       }
     }
 
diff --git a/client/src/app/shared/forms/form-validators/video-channel-validators.service.ts b/client/src/app/shared/forms/form-validators/video-channel-validators.service.ts
index 1ce3a0dcacea..25d6e44840dc 100644
--- a/client/src/app/shared/forms/form-validators/video-channel-validators.service.ts
+++ b/client/src/app/shared/forms/form-validators/video-channel-validators.service.ts
@@ -14,28 +14,28 @@ export class VideoChannelValidatorsService {
     this.VIDEO_CHANNEL_NAME = {
       VALIDATORS: [
         Validators.required,
-        Validators.minLength(3),
-        Validators.maxLength(20),
-        Validators.pattern(/^[a-z0-9._]+$/)
+        Validators.minLength(1),
+        Validators.maxLength(50),
+        Validators.pattern(/^[a-zA-Z0-9][a-zA-Z0-9-._]*$/)
       ],
       MESSAGES: {
         'required': this.i18n('Name is required.'),
-        'minlength': this.i18n('Name must be at least 3 characters long.'),
-        'maxlength': this.i18n('Name cannot be more than 20 characters long.'),
-        'pattern': this.i18n('Name should be only lowercase alphanumeric characters.')
+        'minlength': this.i18n('Name must be at least 1 characters long.'),
+        'maxlength': this.i18n('Name cannot be more than 50 characters long.'),
+        'pattern': this.i18n('Name should start with a letter; numbers, dots, dashes and underscores are allowed.')
       }
     }
 
     this.VIDEO_CHANNEL_DISPLAY_NAME = {
       VALIDATORS: [
         Validators.required,
-        Validators.minLength(3),
-        Validators.maxLength(120)
+        Validators.minLength(1),
+        Validators.maxLength(50)
       ],
       MESSAGES: {
         'required': i18n('Display name is required.'),
-        'minlength': i18n('Display name must be at least 3 characters long.'),
-        'maxlength': i18n('Display name cannot be more than 120 characters long.')
+        'minlength': i18n('Display name must be at least 1 characters long.'),
+        'maxlength': i18n('Display name cannot be more than 50 characters long.')
       }
     }
 
diff --git a/server/initializers/constants.ts b/server/initializers/constants.ts
index e08fd75cd855..2c5b0af74ee7 100644
--- a/server/initializers/constants.ts
+++ b/server/initializers/constants.ts
@@ -291,9 +291,9 @@ const CONFIG = {
 
 const CONSTRAINTS_FIELDS = {
   USERS: {
-    NAME: { min: 3, max: 120 }, // Length
+    NAME: { min: 1, max: 50 }, // Length
     DESCRIPTION: { min: 3, max: 250 }, // Length
-    USERNAME: { min: 3, max: 20 }, // Length
+    USERNAME: { min: 1, max: 50 }, // Length
     PASSWORD: { min: 6, max: 255 }, // Length
     VIDEO_QUOTA: { min: -1 },
     VIDEO_QUOTA_DAILY: { min: -1 },
@@ -307,7 +307,7 @@ const CONSTRAINTS_FIELDS = {
     REASON: { min: 2, max: 300 } // Length
   },
   VIDEO_CHANNELS: {
-    NAME: { min: 3, max: 120 }, // Length
+    NAME: { min: 1, max: 50 }, // Length
     DESCRIPTION: { min: 3, max: 500 }, // Length
     SUPPORT: { min: 3, max: 500 }, // Length
     URL: { min: 3, max: 2000 } // Length
diff --git a/server/tests/api/check-params/users.ts b/server/tests/api/check-params/users.ts
index cbfa0c137cd8..e0f0965f5e0d 100644
--- a/server/tests/api/check-params/users.ts
+++ b/server/tests/api/check-params/users.ts
@@ -99,13 +99,13 @@ describe('Test users API validators', function () {
     }
 
     it('Should fail with a too small username', async function () {
-      const fields = immutableAssign(baseCorrectParams, { username: 'fi' })
+      const fields = immutableAssign(baseCorrectParams, { username: '' })
 
       await makePostBodyRequest({ url: server.url, path, token: server.accessToken, fields })
     })
 
     it('Should fail with a too long username', async function () {
-      const fields = immutableAssign(baseCorrectParams, { username: 'my_super_username_which_is_very_long' })
+      const fields = immutableAssign(baseCorrectParams, { username: 'super'.repeat(11) })
 
       await makePostBodyRequest({ url: server.url, path, token: server.accessToken, fields })
     })
@@ -541,13 +541,13 @@ describe('Test users API validators', function () {
     }
 
     it('Should fail with a too small username', async function () {
-      const fields = immutableAssign(baseCorrectParams, { username: 'ji' })
+      const fields = immutableAssign(baseCorrectParams, { username: '' })
 
       await makePostBodyRequest({ url: server.url, path: registrationPath, token: server.accessToken, fields })
     })
 
     it('Should fail with a too long username', async function () {
-      const fields = immutableAssign(baseCorrectParams, { username: 'my_super_username_which_is_very_long' })
+      const fields = immutableAssign(baseCorrectParams, { username: 'super'.repeat(11) })
 
       await makePostBodyRequest({ url: server.url, path: registrationPath, token: server.accessToken, fields })
     })