diff --git a/.env.vagrant b/.env.vagrant
index 69c1bf1fb3d801..0d17d78554535e 100644
--- a/.env.vagrant
+++ b/.env.vagrant
@@ -5,4 +5,4 @@ DB_HOST=/var/run/postgresql/
 
 ES_ENABLED=true
 ES_HOST=localhost
-ES_PORT=9200
\ No newline at end of file
+ES_PORT=9200
diff --git a/app/controllers/settings/profiles_controller.rb b/app/controllers/settings/profiles_controller.rb
index 8ae69b7fe066d1..8da323f2786991 100644
--- a/app/controllers/settings/profiles_controller.rb
+++ b/app/controllers/settings/profiles_controller.rb
@@ -20,7 +20,7 @@ def update
   private
 
   def account_params
-    params.require(:account).permit(:display_name, :note, :avatar, :header, :bot, fields_attributes: [:name, :value])
+    params.require(:account).permit(:display_name, :note, :avatar, :header, :bot, :account_css, fields_attributes: [:name, :value])
   end
 
   def set_account
diff --git a/app/javascript/flavours/glitch/api_types/accounts.ts b/app/javascript/flavours/glitch/api_types/accounts.ts
index 5bf3e64288c76e..d6dada067b6678 100644
--- a/app/javascript/flavours/glitch/api_types/accounts.ts
+++ b/app/javascript/flavours/glitch/api_types/accounts.ts
@@ -44,4 +44,5 @@ export interface ApiAccountJSON {
   limited?: boolean;
   memorial?: boolean;
   hide_collections: boolean;
+  account_css?: string;
 }
diff --git a/app/javascript/flavours/glitch/features/account/components/header.jsx b/app/javascript/flavours/glitch/features/account/components/header.jsx
index 62c8c84c66eafa..d504ff260cf174 100644
--- a/app/javascript/flavours/glitch/features/account/components/header.jsx
+++ b/app/javascript/flavours/glitch/features/account/components/header.jsx
@@ -3,8 +3,8 @@ import PropTypes from 'prop-types';
 import { defineMessages, injectIntl, FormattedMessage } from 'react-intl';
 
 import classNames from 'classnames';
-import { Helmet } from 'react-helmet';
-import { withRouter } from 'react-router-dom';
+import {Helmet} from 'react-helmet';
+import {withRouter} from 'react-router-dom';
 
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import ImmutablePureComponent from 'react-immutable-pure-component';
@@ -405,6 +405,11 @@ class Header extends ImmutablePureComponent {
           <title>{titleFromAccount(account)}</title>
           <meta name='robots' content={(isLocal && isIndexable) ? 'all' : 'noindex'} />
           <link rel='canonical' href={account.get('url')} />
+          {account.account_css && (
+            <style id={"account-css"} nonce={document.querySelector('meta[name=style-nonce]').content}>
+              {account.account_css}
+            </style>
+          )}
         </Helmet>
       </div>
     );
diff --git a/app/javascript/flavours/glitch/models/account.ts b/app/javascript/flavours/glitch/models/account.ts
index 0b698ead3d1930..eaad1fd3d9a9fb 100644
--- a/app/javascript/flavours/glitch/models/account.ts
+++ b/app/javascript/flavours/glitch/models/account.ts
@@ -95,6 +95,7 @@ export const accountDefaultValues: AccountShape = {
   limited: false,
   moved: null,
   hide_collections: false,
+  account_css: '',
 };
 
 const AccountFactory = ImmutableRecord<AccountShape>(accountDefaultValues);
diff --git a/app/javascript/flavours/glitch/styles/neuromatchstodon/index.scss b/app/javascript/flavours/glitch/styles/neuromatchstodon/index.scss
index 9c3885ff72ad8f..ee9c375fc20f0f 100644
--- a/app/javascript/flavours/glitch/styles/neuromatchstodon/index.scss
+++ b/app/javascript/flavours/glitch/styles/neuromatchstodon/index.scss
@@ -1,3 +1,4 @@
 @import 'latex';
 @import 'bigger_collapsed_statuses';
 @import 'better_code_blocks';
+@import 'myspace';
diff --git a/app/javascript/flavours/glitch/styles/neuromatchstodon/myspace.scss b/app/javascript/flavours/glitch/styles/neuromatchstodon/myspace.scss
new file mode 100644
index 00000000000000..7bcb775aa1a9b9
--- /dev/null
+++ b/app/javascript/flavours/glitch/styles/neuromatchstodon/myspace.scss
@@ -0,0 +1,4 @@
+#account_account_css {
+  font-family: $font-monospace;
+  height: 15em;
+}
diff --git a/app/models/account.rb b/app/models/account.rb
index c344a30bbe98b9..f07cecb4600fa4 100644
--- a/app/models/account.rb
+++ b/app/models/account.rb
@@ -45,12 +45,13 @@
 #  avatar_storage_schema_version :integer
 #  header_storage_schema_version :integer
 #  devices_url                   :string
-#  suspension_origin             :integer
 #  sensitized_at                 :datetime
+#  suspension_origin             :integer
 #  trendable                     :boolean
 #  reviewed_at                   :datetime
 #  requested_review_at           :datetime
 #  indexable                     :boolean          default(FALSE), not null
+#  account_css                   :text
 #
 
 class Account < ApplicationRecord
@@ -114,6 +115,7 @@ class Account < ApplicationRecord
   validates :followers_url, absence: true, if: :local?, on: :create
 
   normalizes :username, with: ->(username) { username.squish }
+  normalizes :account_css, with: ->(account_css) { Sanitize::CSS.stylesheet(account_css, Sanitize::Config::RELAXED) }
 
   scope :without_internal, -> { where(id: 1...) }
   scope :remote, -> { where.not(domain: nil) }
diff --git a/app/serializers/rest/account_serializer.rb b/app/serializers/rest/account_serializer.rb
index a10d6988817370..dbaa15944b5e28 100644
--- a/app/serializers/rest/account_serializer.rb
+++ b/app/serializers/rest/account_serializer.rb
@@ -8,7 +8,8 @@ class REST::AccountSerializer < ActiveModel::Serializer
 
   attributes :id, :username, :acct, :display_name, :locked, :bot, :discoverable, :indexable, :group, :created_at,
              :note, :url, :uri, :avatar, :avatar_static, :header, :header_static,
-             :followers_count, :following_count, :statuses_count, :last_status_at, :hide_collections
+             :followers_count, :following_count, :statuses_count, :last_status_at, :hide_collections,
+             :account_css
 
   has_one :moved_to_account, key: :moved, serializer: REST::AccountSerializer, if: :moved_and_not_nested?
 
diff --git a/app/views/settings/profiles/show.html.haml b/app/views/settings/profiles/show.html.haml
index 61ba79c4491f02..fc44f01402e1d1 100644
--- a/app/views/settings/profiles/show.html.haml
+++ b/app/views/settings/profiles/show.html.haml
@@ -67,5 +67,10 @@
   .fields-group
     = f.input :bot, as: :boolean, wrapper: :with_label, hint: t('simple_form.hints.defaults.bot')
 
+  %h4= t 'edit_profile.myspace_mode'
+
+  .fields-group
+    = f.input :account_css, as: :text, wrapper: :with_block_label, label: I18n.t('simple_form.labels.account.account_css'), hint: I18n.t('simple_form.hints.account.account_css'), neuromatchstodon_only: true
+
   .actions
     = f.button :button, t('generic.save_changes'), type: :submit
diff --git a/config/initializers/simple_form.rb b/config/initializers/simple_form.rb
index 2fd87acc8aca64..fc7fc21999ce0d 100644
--- a/config/initializers/simple_form.rb
+++ b/config/initializers/simple_form.rb
@@ -38,10 +38,20 @@ def glitch_only(_wrapper_options = nil)
   end
 end
 
+module NeuromatchstodonOnlyComponent
+  def neuromatchstodon_only(_wrapper_options = nil)
+    return unless options[:neuromatchstodon_only]
+
+    options[:label_text] = ->(raw_label_text, _required_label_text, _label_present) { safe_join([raw_label_text, ' ', content_tag(:span, I18n.t('simple_form.neuromatchstodon_only'), class: 'glitch_only')]) }
+    nil
+  end
+end
+
 SimpleForm.include_component(AppendComponent)
 SimpleForm.include_component(RecommendedComponent)
 SimpleForm.include_component(WarningHintComponent)
 SimpleForm.include_component(GlitchOnlyComponent)
+SimpleForm.include_component(NeuromatchstodonOnlyComponent)
 
 SimpleForm.setup do |config|
   # Wrappers are used by the form builder to generate a
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 1df9af88d95306..dccc71a8b65e9c 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -1236,6 +1236,7 @@ en:
     basic_information: Basic information
     hint_html: "<strong>Customize what people see on your public profile and next to your posts.</strong> Other people are more likely to follow you back and interact with you when you have a filled out profile and a profile picture."
     other: Other
+    myspace_mode: "MySpace Mode"
   errors:
     '400': The request you submitted was invalid or malformed.
     '403': You don't have permission to view this page.
diff --git a/config/locales/simple_form.en.yml b/config/locales/simple_form.en.yml
index fee3a6151ad419..9300b0f862d076 100644
--- a/config/locales/simple_form.en.yml
+++ b/config/locales/simple_form.en.yml
@@ -10,6 +10,7 @@ en:
         note: 'You can @mention other people or #hashtags.'
         show_collections: People will be able to browse through your follows and followers. People that you follow will see that you follow them regardless.
         unlocked: People will be able to follow you without requesting approval. Uncheck if you want to review follow requests and chose whether to accept or reject new followers.
+        account_css: Custom CSS that is applied to your account page
       account_alias:
         acct: Specify the username@domain of the account you want to move from
       account_migration:
@@ -150,6 +151,7 @@ en:
         indexable: Include public posts in search results
         show_collections: Show follows and followers on profile
         unlocked: Automatically accept new followers
+        account_css: Account CSS
       account_alias:
         acct: Handle of the old account
       account_migration:
@@ -339,3 +341,4 @@ en:
       sessions:
         webauthn: Use one of your security keys to sign in
     'yes': 'Yes'
+    neuromatchstodon_only: "Neuromatchstodon Only"
diff --git a/db/migrate/20240828084252_add_account_css_to_account.rb b/db/migrate/20240828084252_add_account_css_to_account.rb
new file mode 100644
index 00000000000000..01a14f31f37a37
--- /dev/null
+++ b/db/migrate/20240828084252_add_account_css_to_account.rb
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddAccountCssToAccount < ActiveRecord::Migration[7.1]
+  def change
+    add_column :accounts, :account_css, :text, null: true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index a3afab78167fe8..5ac44d4d653c3f 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2024_08_08_125420) do
+ActiveRecord::Schema[7.1].define(version: 2024_08_28_084252) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -200,6 +200,7 @@
     t.datetime "reviewed_at", precision: nil
     t.datetime "requested_review_at", precision: nil
     t.boolean "indexable", default: false, null: false
+    t.text "account_css"
     t.index "(((setweight(to_tsvector('simple'::regconfig, (display_name)::text), 'A'::\"char\") || setweight(to_tsvector('simple'::regconfig, (username)::text), 'B'::\"char\")) || setweight(to_tsvector('simple'::regconfig, (COALESCE(domain, ''::character varying))::text), 'C'::\"char\")))", name: "search_index", using: :gin
     t.index "lower((username)::text), COALESCE(lower((domain)::text), ''::text)", name: "index_accounts_on_username_and_domain_lower", unique: true
     t.index ["domain", "id"], name: "index_accounts_on_domain_and_id"
@@ -1428,9 +1429,9 @@
   add_index "instances", ["domain"], name: "index_instances_on_domain", unique: true
 
   create_view "user_ips", sql_definition: <<-SQL
-      SELECT user_id,
-      ip,
-      max(used_at) AS used_at
+      SELECT t0.user_id,
+      t0.ip,
+      max(t0.used_at) AS used_at
      FROM ( SELECT users.id AS user_id,
               users.sign_up_ip AS ip,
               users.created_at AS used_at
@@ -1447,7 +1448,7 @@
               login_activities.created_at
              FROM login_activities
             WHERE (login_activities.success = true)) t0
-    GROUP BY user_id, ip;
+    GROUP BY t0.user_id, t0.ip;
   SQL
   create_view "account_summaries", materialized: true, sql_definition: <<-SQL
       SELECT accounts.id AS account_id,
@@ -1468,9 +1469,9 @@
   add_index "account_summaries", ["account_id"], name: "index_account_summaries_on_account_id", unique: true
 
   create_view "global_follow_recommendations", materialized: true, sql_definition: <<-SQL
-      SELECT account_id,
-      sum(rank) AS rank,
-      array_agg(reason) AS reason
+      SELECT t0.account_id,
+      sum(t0.rank) AS rank,
+      array_agg(t0.reason) AS reason
      FROM ( SELECT account_summaries.account_id,
               ((count(follows.id))::numeric / (1.0 + (count(follows.id))::numeric)) AS rank,
               'most_followed'::text AS reason
@@ -1494,8 +1495,8 @@
                     WHERE (follow_recommendation_suppressions.account_id = statuses.account_id)))))
             GROUP BY account_summaries.account_id
            HAVING (sum((status_stats.reblogs_count + status_stats.favourites_count)) >= (5)::numeric)) t0
-    GROUP BY account_id
-    ORDER BY (sum(rank)) DESC;
+    GROUP BY t0.account_id
+    ORDER BY (sum(t0.rank)) DESC;
   SQL
   add_index "global_follow_recommendations", ["account_id"], name: "index_global_follow_recommendations_on_account_id", unique: true
 
diff --git a/spec/controllers/settings/profiles_controller_spec.rb b/spec/controllers/settings/profiles_controller_spec.rb
index e3197f0a6d7882..6450c95444c884 100644
--- a/spec/controllers/settings/profiles_controller_spec.rb
+++ b/spec/controllers/settings/profiles_controller_spec.rb
@@ -48,4 +48,31 @@
       expect(ActivityPub::UpdateDistributionWorker).to have_received(:perform_async).with(account.id)
     end
   end
+
+  describe 'PUT #account_css with custom css' do
+    it 'hopefully removes malicious css' do
+      put :update, params: {
+        account: {
+          account_css: <<~CSS,
+            @import url(swear_words.css);
+            a { text-decoration: none; }
+
+            a:hover {
+            left: expression(alert('xss!'));
+            text-decoration: underline;
+            }
+          CSS
+        },
+      }
+      expect(account.reload.account_css).to eq <<~CSS
+
+        a { text-decoration: none; }
+
+        a:hover {
+
+        text-decoration: underline;
+        }
+      CSS
+    end
+  end
 end
diff --git a/spec/support/stories/profile_stories.rb b/spec/support/stories/profile_stories.rb
index 07eaaca9fb93b0..45c02875a28aab 100644
--- a/spec/support/stories/profile_stories.rb
+++ b/spec/support/stories/profile_stories.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module ProfileStories
-  attr_reader :bob, :alice, :alice_bio
+  attr_reader :bob, :alice, :alice_bio, :chupacabra, :chupacabra_css
 
   def fill_in_auth_details(email, password)
     fill_in 'user_email', with: email
@@ -43,6 +43,21 @@ def with_alice_as_local_user
     )
   end
 
+  def with_chupacabras_fancy_profile
+    @chupacabra_css = <<~CSS
+      body {
+        background-color: red !important;
+      }
+    CSS
+
+    @chupacabra = Fabricate(
+      :user,
+      email: 'chupacabra@example.com', password: password, confirmed_at: confirmed_at,
+      account: Fabricate(:account, username: 'chupacabra', note: 'I am gonna getcha!', account_css: @chupacabra_css)
+    )
+    Web::Setting.where(user: chupacabra).first_or_initialize(user: chupacabra).update!(data: { introductionVersion: 2018_12_16_044202 })
+  end
+
   def confirmed_at
     @confirmed_at ||= Time.zone.now
   end
diff --git a/spec/system/profile_spec.rb b/spec/system/profile_spec.rb
index 2517e823b50c5f..cb8e74285ed868 100644
--- a/spec/system/profile_spec.rb
+++ b/spec/system/profile_spec.rb
@@ -30,4 +30,21 @@
 
     expect(subject).to have_content 'Changes successfully saved!'
   end
+
+  describe 'with JS', :js, :streaming do
+    before do
+      with_chupacabras_fancy_profile
+    end
+
+    it 'Can have custom account_css set' do
+      visit account_path('chupacabra')
+      # wait for page to load...
+      page.find '.account__header'
+      expect(subject.html).to have_content('background-color: red !important')
+
+      visit account_path('bob')
+      page.find '.account__header'
+      expect(subject.html).to have_no_content('background-color: red !important')
+    end
+  end
 end