diff --git a/app/assets/javascripts/discourse-common/addon/resolver.js b/app/assets/javascripts/discourse-common/addon/resolver.js
index 7ad517b2c46..4fcc1966d15 100644
--- a/app/assets/javascripts/discourse-common/addon/resolver.js
+++ b/app/assets/javascripts/discourse-common/addon/resolver.js
@@ -52,6 +52,24 @@ export function buildResolver(baseName) {
         return "service:app-events";
       }
 
+      for (const [key, value] of Object.entries({
+        "controller:discovery.categoryWithID": "controller:discovery.category",
+        "controller:discovery.parentCategory": "controller:discovery.category",
+        "controller:tags-show": "controller:tag-show",
+        "controller:tags.show": "controller:tag.show",
+        "controller:tagsShow": "controller:tagShow",
+        "route:discovery.categoryWithID": "route:discovery.category",
+        "route:discovery.parentCategory": "route:discovery.category",
+        "route:tags-show": "route:tag-show",
+        "route:tags.show": "route:tag.show",
+        "route:tagsShow": "route:tagShow",
+      })) {
+        if (fullName === key) {
+          deprecated(`${key} was replaced with ${value}`, { since: "2.6.0" });
+          return value;
+        }
+      }
+
       const split = fullName.split(":");
       if (split.length > 1) {
         const appBase = `${baseName}/${split[0]}s/`;
diff --git a/app/assets/javascripts/discourse/app/controllers/rename-tag.js b/app/assets/javascripts/discourse/app/controllers/rename-tag.js
index 0993aa852e1..64a17026d7a 100644
--- a/app/assets/javascripts/discourse/app/controllers/rename-tag.js
+++ b/app/assets/javascripts/discourse/app/controllers/rename-tag.js
@@ -26,7 +26,7 @@ export default Controller.extend(ModalFunctionality, BufferedContent, {
           this.send("closeModal");
 
           if (result.responseJson.tag) {
-            this.transitionToRoute("tags.show", result.responseJson.tag.id);
+            this.transitionToRoute("tag.show", result.responseJson.tag.id);
           } else {
             this.flash(extractError(result.responseJson.errors[0]), "error");
           }
diff --git a/app/assets/javascripts/discourse/app/controllers/tags-show.js b/app/assets/javascripts/discourse/app/controllers/tag-show.js
similarity index 100%
rename from app/assets/javascripts/discourse/app/controllers/tags-show.js
rename to app/assets/javascripts/discourse/app/controllers/tag-show.js
diff --git a/app/assets/javascripts/discourse/app/models/nav-item.js b/app/assets/javascripts/discourse/app/models/nav-item.js
index d0979d4f8ba..ae8caa882c7 100644
--- a/app/assets/javascripts/discourse/app/models/nav-item.js
+++ b/app/assets/javascripts/discourse/app/models/nav-item.js
@@ -122,7 +122,7 @@ NavItem.reopenClass({
 
     if (context.tagId && Site.currentProp("filters").includes(filterType)) {
       includesTagContext = true;
-      path += "/tags";
+      path += "/tag";
     }
 
     if (context.category) {
diff --git a/app/assets/javascripts/discourse/app/pre-initializers/dynamic-route-builders.js b/app/assets/javascripts/discourse/app/pre-initializers/dynamic-route-builders.js
index 66febe7f1bf..aada8bab6b7 100644
--- a/app/assets/javascripts/discourse/app/pre-initializers/dynamic-route-builders.js
+++ b/app/assets/javascripts/discourse/app/pre-initializers/dynamic-route-builders.js
@@ -1,7 +1,7 @@
 import buildCategoryRoute from "discourse/routes/build-category-route";
 import buildTopicRoute from "discourse/routes/build-topic-route";
 import DiscoverySortableController from "discourse/controllers/discovery-sortable";
-import TagsShowRoute from "discourse/routes/tags-show";
+import TagShowRoute from "discourse/routes/tag-show";
 import Site from "discourse/models/site";
 import User from "discourse/models/user";
 
@@ -11,20 +11,16 @@ export default {
 
   initialize(registry, app) {
     app.DiscoveryCategoryController = DiscoverySortableController.extend();
-    app.DiscoveryParentCategoryController = DiscoverySortableController.extend();
     app.DiscoveryCategoryNoneController = DiscoverySortableController.extend();
     app.DiscoveryCategoryAllController = DiscoverySortableController.extend();
-    app.DiscoveryCategoryWithIDController = DiscoverySortableController.extend();
 
     app.DiscoveryCategoryRoute = buildCategoryRoute("default");
-    app.DiscoveryParentCategoryRoute = buildCategoryRoute("default");
     app.DiscoveryCategoryNoneRoute = buildCategoryRoute("default", {
       no_subcategories: true,
     });
     app.DiscoveryCategoryAllRoute = buildCategoryRoute("default", {
       no_subcategories: false,
     });
-    app.DiscoveryCategoryWithIDRoute = buildCategoryRoute("default");
 
     const site = Site.current();
     site.get("filters").forEach((filter) => {
@@ -35,9 +31,6 @@ export default {
       app[
         `Discovery${filterCapitalized}CategoryController`
       ] = DiscoverySortableController.extend();
-      app[
-        `Discovery${filterCapitalized}ParentCategoryController`
-      ] = DiscoverySortableController.extend();
       app[
         `Discovery${filterCapitalized}CategoryNoneController`
       ] = DiscoverySortableController.extend();
@@ -48,9 +41,6 @@ export default {
       app[`Discovery${filterCapitalized}CategoryRoute`] = buildCategoryRoute(
         filter
       );
-      app[
-        `Discovery${filterCapitalized}ParentCategoryRoute`
-      ] = buildCategoryRoute(filter);
       app[
         `Discovery${filterCapitalized}CategoryNoneRoute`
       ] = buildCategoryRoute(filter, { no_subcategories: true });
@@ -74,9 +64,6 @@ export default {
       app[
         `DiscoveryTop${periodCapitalized}CategoryController`
       ] = DiscoverySortableController.extend();
-      app[
-        `DiscoveryTop${periodCapitalized}ParentCategoryController`
-      ] = DiscoverySortableController.extend();
       app[
         `DiscoveryTop${periodCapitalized}CategoryNoneController`
       ] = DiscoverySortableController.extend();
@@ -86,38 +73,26 @@ export default {
       app[`DiscoveryTop${periodCapitalized}CategoryRoute`] = buildCategoryRoute(
         "top/" + period
       );
-      app[
-        `DiscoveryTop${periodCapitalized}ParentCategoryRoute`
-      ] = buildCategoryRoute("top/" + period);
       app[
         `DiscoveryTop${periodCapitalized}CategoryNoneRoute`
       ] = buildCategoryRoute("top/" + period, { no_subcategories: true });
     });
 
-    app["TagsShowCategoryRoute"] = TagsShowRoute.extend();
-    app["TagsShowCategoryNoneRoute"] = TagsShowRoute.extend({
+    app["TagsShowCategoryRoute"] = TagShowRoute.extend();
+    app["TagsShowCategoryNoneRoute"] = TagShowRoute.extend({
       noSubcategories: true,
     });
-    app["TagsShowParentCategoryRoute"] = TagsShowRoute.extend();
-
-    app["TagShowRoute"] = TagsShowRoute;
 
     site.get("filters").forEach(function (filter) {
-      app["TagsShow" + filter.capitalize() + "Route"] = TagsShowRoute.extend({
-        navMode: filter,
-      });
-      app["TagShow" + filter.capitalize() + "Route"] = TagsShowRoute.extend({
+      app["TagShow" + filter.capitalize() + "Route"] = TagShowRoute.extend({
         navMode: filter,
       });
       app[
         "TagsShowCategory" + filter.capitalize() + "Route"
-      ] = TagsShowRoute.extend({ navMode: filter });
+      ] = TagShowRoute.extend({ navMode: filter });
       app[
         "TagsShowNoneCategory" + filter.capitalize() + "Route"
-      ] = TagsShowRoute.extend({ navMode: filter, noSubcategories: true });
-      app[
-        "TagsShowParentCategory" + filter.capitalize() + "Route"
-      ] = TagsShowRoute.extend({ navMode: filter });
+      ] = TagShowRoute.extend({ navMode: filter, noSubcategories: true });
     });
   },
 };
diff --git a/app/assets/javascripts/discourse/app/routes/app-route-map.js b/app/assets/javascripts/discourse/app/routes/app-route-map.js
index c3c5f17193f..5352b1ff7c9 100644
--- a/app/assets/javascripts/discourse/app/routes/app-route-map.js
+++ b/app/assets/javascripts/discourse/app/routes/app-route-map.js
@@ -34,9 +34,6 @@ export default function () {
   );
 
   this.route("discovery", { path: "/", resetNamespace: true }, function () {
-    // legacy route
-    this.route("topParentCategory", { path: "/c/:slug/l/top" });
-
     // top
     this.route("top");
     this.route("topCategoryNone", {
@@ -48,9 +45,6 @@ export default function () {
     Site.currentProp("periods").forEach((period) => {
       const top = "top" + period.capitalize();
 
-      // legacy route
-      this.route(top + "ParentCategory", { path: "/c/:slug/l/top/" + period });
-
       this.route(top, { path: "/top/" + period });
       this.route(top + "CategoryNone", {
         path: "/c/*category_slug_path_with_id/none/l/top/" + period,
@@ -62,9 +56,6 @@ export default function () {
 
     // filters (e.g. bookmarks, posted, read, unread, latest)
     Site.currentProp("filters").forEach((filter) => {
-      // legacy route
-      this.route(filter + "ParentCategory", { path: "/c/:slug/l/" + filter });
-
       this.route(filter, { path: "/" + filter });
       this.route(filter + "CategoryNone", {
         path: "/c/*category_slug_path_with_id/none/l/" + filter,
@@ -76,10 +67,6 @@ export default function () {
 
     this.route("categories");
 
-    // legacy routes
-    this.route("parentCategory", { path: "/c/:slug" });
-    this.route("categoryWithID", { path: "/c/:parentSlug/:slug/:id" });
-
     // default filter for a category
     this.route("categoryNone", { path: "/c/*category_slug_path_with_id/none" });
     this.route("categoryAll", { path: "/c/*category_slug_path_with_id/all" });
@@ -259,14 +246,6 @@ export default function () {
     this.route("intersection", {
       path: "intersection/:tag_id/*additional_tags",
     });
-
-    // legacy routes
-    this.route("show", { path: "/:tag_id" });
-    Site.currentProp("filters").forEach((filter) => {
-      this.route("show" + filter.capitalize(), {
-        path: "/:tag_id/l/" + filter,
-      });
-    });
   });
 
   this.route(
diff --git a/app/assets/javascripts/discourse/app/routes/new-topic.js b/app/assets/javascripts/discourse/app/routes/new-topic.js
index c82cc0681d3..538254dff0c 100644
--- a/app/assets/javascripts/discourse/app/routes/new-topic.js
+++ b/app/assets/javascripts/discourse/app/routes/new-topic.js
@@ -33,17 +33,9 @@ export default DiscourseRoute.extend({
         }
       }
 
-      if (Boolean(category)) {
-        let route = "discovery.parentCategory";
-        let params = { category, slug: category.slug };
-        if (category.parentCategory) {
-          route = "discovery.category";
-          params = {
-            category,
-            parentSlug: category.parentCategory.slug,
-            slug: category.slug,
-          };
-        }
+      if (category) {
+        let route = "discovery.category";
+        let params = { category, id: category.id };
 
         this.replaceWith(route, params).then((e) => {
           if (this.controllerFor("navigation/category").canCreateTopic) {
diff --git a/app/assets/javascripts/discourse/app/routes/tags-show.js b/app/assets/javascripts/discourse/app/routes/tag-show.js
similarity index 95%
rename from app/assets/javascripts/discourse/app/routes/tags-show.js
rename to app/assets/javascripts/discourse/app/routes/tag-show.js
index c6d2aa7a294..8fec14ea398 100644
--- a/app/assets/javascripts/discourse/app/routes/tags-show.js
+++ b/app/assets/javascripts/discourse/app/routes/tag-show.js
@@ -23,7 +23,7 @@ export default DiscourseRoute.extend(FilterModeMixin, {
   queryParams,
 
   renderTemplate() {
-    const controller = this.controllerFor("tags.show");
+    const controller = this.controllerFor("tag.show");
     this.render("tags.show", { controller });
   },
 
@@ -62,7 +62,7 @@ export default DiscourseRoute.extend(FilterModeMixin, {
   },
 
   afterModel(tag, transition) {
-    const controller = this.controllerFor("tags.show");
+    const controller = this.controllerFor("tag.show");
     controller.setProperties({
       loading: true,
       showInfo: false,
@@ -122,7 +122,7 @@ export default DiscourseRoute.extend(FilterModeMixin, {
     const filterText = I18n.t(
       `filters.${this.navMode.replace("/", ".")}.title`
     );
-    const controller = this.controllerFor("tags.show");
+    const controller = this.controllerFor("tag.show");
 
     if (controller.get("model.id")) {
       if (this.category) {
@@ -152,7 +152,7 @@ export default DiscourseRoute.extend(FilterModeMixin, {
   },
 
   setupController(controller, model) {
-    this.controllerFor("tags.show").setProperties({
+    this.controllerFor("tag.show").setProperties({
       model,
       tag: model,
       additionalTags: this.additionalTags,
@@ -180,7 +180,7 @@ export default DiscourseRoute.extend(FilterModeMixin, {
     },
 
     createTopic() {
-      const controller = this.controllerFor("tags.show");
+      const controller = this.controllerFor("tag.show");
 
       if (controller.get("list.draft")) {
         this.openTopicDraft(controller.get("list"));
@@ -233,7 +233,7 @@ export default DiscourseRoute.extend(FilterModeMixin, {
     resetParams,
 
     didTransition() {
-      this.controllerFor("tags.show")._showFooter();
+      this.controllerFor("tag.show")._showFooter();
       return true;
     },
   },
diff --git a/app/assets/javascripts/discourse/app/routes/tags-intersection.js b/app/assets/javascripts/discourse/app/routes/tags-intersection.js
index e8b784f0eed..7dd65e72b1c 100644
--- a/app/assets/javascripts/discourse/app/routes/tags-intersection.js
+++ b/app/assets/javascripts/discourse/app/routes/tags-intersection.js
@@ -1,6 +1,6 @@
-import TagsShowRoute from "discourse/routes/tags-show";
+import TagShowRoute from "discourse/routes/tag-show";
 
-export default TagsShowRoute.extend({});
+export default TagShowRoute.extend({});
 
 // The tags-intersection route is exactly the same as the tags-show route, but the wildcard at the
 // end of the route (*additional_tags) will cause a match when query parameters are present,
diff --git a/app/controllers/list_controller.rb b/app/controllers/list_controller.rb
index 24797d6b8f2..910e2ed5d84 100644
--- a/app/controllers/list_controller.rb
+++ b/app/controllers/list_controller.rb
@@ -336,25 +336,14 @@ class ListController < ApplicationController
   end
 
   def set_category
-    parts = params.require(:category_slug_path_with_id).split('/')
+    category_slug_path_with_id = params.require(:category_slug_path_with_id)
 
-    if !parts.empty? && parts.last =~ /\A\d+\Z/
-      id = parts.pop.to_i
-    end
-    slug_path = parts unless parts.empty?
-
-    if id.present?
-      @category = Category.find_by_id(id)
-    elsif slug_path.present?
-      @category = Category.find_by_slug_path(slug_path)
-
-      # Legacy paths
-      if @category.nil? && parts.last =~ /\A\d+-category/
-        @category = Category.find_by_id(parts.last.to_i)
-      end
+    @category = Category.find_by_slug_path_with_id(category_slug_path_with_id)
+    if @category.nil?
+      raise Discourse::NotFound.new("category not found", check_permalinks: true)
     end
 
-    raise Discourse::NotFound.new("category not found", check_permalinks: true) if @category.nil?
+    params[:category] = @category.id.to_s
 
     if !guardian.can_see?(@category)
       if SiteSetting.detailed_404
@@ -364,13 +353,13 @@ class ListController < ApplicationController
       end
     end
 
-    current_slug = params.require(:category_slug_path_with_id)
-    real_slug = @category.full_slug("/")
-
+    # Check if the category slug is incorrect and redirect to a link containing
+    # the correct one.
+    current_slug = category_slug_path_with_id
     if SiteSetting.slug_generation_method == "encoded"
       current_slug = current_slug.split("/").map { |slug| CGI.escape(slug) }.join("/")
     end
-
+    real_slug = @category.full_slug("/")
     if current_slug != real_slug
       url = request.fullpath.gsub(current_slug, real_slug)
       if ActionController::Base.config.relative_url_root
@@ -380,14 +369,13 @@ class ListController < ApplicationController
       return redirect_to path(url), status: 301
     end
 
-    params[:category] = @category.id.to_s
-
     @description_meta = if @category.uncategorized?
-      I18n.t('category.uncategorized_description', locale: SiteSetting.default_locale)
-    else
+      I18n.t("category.uncategorized_description", locale: SiteSetting.default_locale)
+    elsif @category.description_text.present?
       @category.description_text
+    else
+      SiteSetting.site_description
     end
-    @description_meta = SiteSetting.site_description if @description_meta.blank?
 
     if use_crawler_layout?
       @subcategories = @category.subcategories.select { |c| guardian.can_see?(c) }
diff --git a/app/controllers/tags_controller.rb b/app/controllers/tags_controller.rb
index c6e5810a4e5..bc2e5c106b2 100644
--- a/app/controllers/tags_controller.rb
+++ b/app/controllers/tags_controller.rb
@@ -18,7 +18,7 @@ class TagsController < ::ApplicationController
 
   skip_before_action :check_xhr, only: [:tag_feed, :show, :index]
 
-  before_action :set_category_from_params, except: [:index, :update, :destroy,
+  before_action :set_category, except: [:index, :update, :destroy,
     :tag_feed, :search, :notifications, :update_notifications, :personal_messages, :info]
 
   before_action :fetch_tag, only: [:info, :create_synonyms, :destroy_synonym]
@@ -92,8 +92,9 @@ class TagsController < ::ApplicationController
       @description_meta = I18n.t("rss_by_tag", tag: tag_params.join(' & '))
       @title = @description_meta
 
-      path_name = url_method(params.slice(:category, :parent_category))
-      canonical_url "#{Discourse.base_url_no_prefix}#{public_send(path_name, *(params.slice(:parent_category, :category, :tag_id).values.map { |t| t.force_encoding("UTF-8") }))}"
+      canonical_params = params.slice(:category_slug_path_with_id, :tag_id)
+      canonical_method = url_method(canonical_params)
+      canonical_url "#{Discourse.base_url_no_prefix}#{public_send(canonical_method, *(canonical_params.values.map { |t| t.force_encoding("UTF-8") }))}"
 
       if @list.topics.size == 0 && params[:tag_id] != 'none' && !Tag.where_name(@tag_id).exists?
         raise Discourse::NotFound.new("tag not found", check_permalinks: true)
@@ -347,25 +348,9 @@ class TagsController < ::ApplicationController
     end.compact
   end
 
-  def set_category_from_params
+  def set_category
     if request.path_parameters.include?(:category_slug_path_with_id)
-      parts = params[:category_slug_path_with_id].split('/')
-
-      if !parts.empty? && parts.last =~ /\A\d+\Z/
-        id = parts.pop.to_i
-      end
-      slug_path = parts unless parts.empty?
-
-      if id.present?
-        @filter_on_category = Category.find_by_id(id)
-      elsif slug_path.present?
-        @filter_on_category = Category.find_by_slug_path(slug_path)
-
-        # Legacy paths
-        if @filter_on_category.nil? && parts.last =~ /\A\d+-category/
-          @filter_on_category = Category.find_by_id(parts.last.to_i)
-        end
-      end
+      @filter_on_category = Category.find_by_slug_path_with_id(params[:category_slug_path_with_id])
     else
       slug_or_id = params[:category]
       return true if slug_or_id.nil?
@@ -373,9 +358,16 @@ class TagsController < ::ApplicationController
       @filter_on_category = Category.query_category(slug_or_id, nil)
     end
 
-    category_redirect_or_not_found && (return) if !@filter_on_category
-
     guardian.ensure_can_see!(@filter_on_category)
+
+    if !@filter_on_category
+      permalink = Permalink.find_by_url("c/#{params[:category_slug_path_with_id]}")
+      if permalink.present? && permalink.category_id
+        return redirect_to "#{Discourse::base_path}/tags#{permalink.target_url}/#{params[:tag_id]}", status: :moved_permanently
+      end
+
+      raise Discourse::NotFound
+    end
   end
 
   def page_params
@@ -409,9 +401,7 @@ class TagsController < ::ApplicationController
   end
 
   def url_method(opts = {})
-    if opts[:parent_category] && opts[:category]
-      "tag_parent_category_category_#{action_name}_path"
-    elsif opts[:category]
+    if opts[:category_slug_path_with_id]
       "tag_category_#{action_name}_path"
     else
       "tag_#{action_name}_path"
@@ -472,19 +462,6 @@ class TagsController < ::ApplicationController
     options
   end
 
-  def category_redirect_or_not_found
-    # automatic redirects for renamed categories
-    url = params[:parent_category] ? "c/#{params[:parent_category]}/#{params[:category]}" : "c/#{params[:category]}"
-    permalink = Permalink.find_by_url(url)
-
-    if permalink.present? && permalink.category_id
-      redirect_to "#{Discourse.base_path}/tags#{permalink.target_url}/#{params[:tag_id]}", status: :moved_permanently
-    else
-      # redirect to 404
-      raise Discourse::NotFound
-    end
-  end
-
   def tag_params
     [@tag_id].concat(Array(@additional_tags))
   end
diff --git a/app/models/category.rb b/app/models/category.rb
index 13202e4b521..2623b153de5 100644
--- a/app/models/category.rb
+++ b/app/models/category.rb
@@ -810,6 +810,17 @@ class Category < ActiveRecord::Base
     Category.find_by_id(query)
   end
 
+  def self.find_by_slug_path_with_id(slug_path_with_id)
+    slug_path = slug_path_with_id.split("/")
+
+    if slug_path.last =~ /\A\d+\Z/
+      id = slug_path.pop.to_i
+      Category.find_by_id(id)
+    else
+      Category.find_by_slug_path(slug_path)
+    end
+  end
+
   def self.find_by_slug(category_slug, parent_category_slug = nil)
     return nil if category_slug.nil?
 
diff --git a/app/models/topic_list.rb b/app/models/topic_list.rb
index 8ab04925807..f191af9e5a0 100644
--- a/app/models/topic_list.rb
+++ b/app/models/topic_list.rb
@@ -59,7 +59,7 @@ class TopicList < DraftableList
   def top_tags
     opts = @category ? { category: @category } : {}
     opts[:guardian] = Guardian.new(@current_user)
-    Tag.top_tags(opts)
+    Tag.top_tags(**opts)
   end
 
   def preload_key
diff --git a/config/routes.rb b/config/routes.rb
index 791621e5f4e..c06c1cd3e33 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -921,23 +921,6 @@ Discourse::Application.routes.draw do
 
         get '/intersection/:tag_id/*additional_tag_ids' => 'tags#show', as: 'tag_intersection'
       end
-
-      # legacy routes
-      constraints(tag_id: /[^\/]+?/, format: /json|rss/) do
-        get '/:tag_id.rss' => 'tags#tag_feed'
-        get '/:tag_id' => 'tags#show'
-        get '/:tag_id/info' => 'tags#info'
-        get '/:tag_id/notifications' => 'tags#notifications'
-        put '/:tag_id/notifications' => 'tags#update_notifications'
-        put '/:tag_id' => 'tags#update'
-        delete '/:tag_id' => 'tags#destroy'
-        post '/:tag_id/synonyms' => 'tags#create_synonyms'
-        delete '/:tag_id/synonyms/:synonym_id' => 'tags#destroy_synonym'
-
-        Discourse.filters.each do |filter|
-          get "/:tag_id/l/#{filter}" => "tags#show_#{filter}"
-        end
-      end
     end
 
     resources :tag_groups, constraints: StaffConstraint.new, except: [:edit] do
diff --git a/spec/requests/api/tags_spec.rb b/spec/requests/api/tags_spec.rb
index 7ef2a23bd4f..b5c53cf4fb7 100644
--- a/spec/requests/api/tags_spec.rb
+++ b/spec/requests/api/tags_spec.rb
@@ -235,7 +235,7 @@ describe 'tags' do
     end
   end
 
-  path '/tags/{name}.json' do
+  path '/tag/{name}.json' do
 
     get 'Get a specific tag' do
       tags 'Tags'