diff --git a/Telegram/SourceFiles/core/local_url_handlers.cpp b/Telegram/SourceFiles/core/local_url_handlers.cpp
index de59f999a..da9879415 100644
--- a/Telegram/SourceFiles/core/local_url_handlers.cpp
+++ b/Telegram/SourceFiles/core/local_url_handlers.cpp
@@ -39,6 +39,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "mainwidget.h"
 #include "main/main_session.h"
 #include "main/main_session_settings.h"
+#include "history/history.h"
 #include "apiwrap.h"
 
 #include <QtGui/QGuiApplication>
@@ -464,6 +465,29 @@ bool ShowInviteLink(
 	return true;
 }
 
+bool ResolveTestChatTheme(
+		Window::SessionController *controller,
+		const Match &match,
+		const QVariant &context) {
+	if (!controller) {
+		return false;
+	}
+	const auto params = url_parse_params(
+		match->captured(1),
+		qthelp::UrlParamNameTransform::ToLower);
+	if (const auto history = controller->activeChatCurrent().history()) {
+		controller->clearCachedChatThemes();
+		const auto theme = history->owner().cloudThemes().updateThemeFromLink(
+			history->peer->themeEmoji(),
+			params);
+		if (theme) {
+			[[maybe_unused]] auto value = controller->cachedChatThemeValue(
+				*theme);
+		}
+	}
+	return true;
+}
+
 } // namespace
 
 const std::vector<LocalUrlHandler> &LocalUrlHandlers() {
@@ -524,6 +548,10 @@ const std::vector<LocalUrlHandler> &LocalUrlHandlers() {
 			qsl("^settings(/folders|/devices|/language)?$"),
 			ResolveSettings
 		},
+		{
+			qsl("^test_chat_theme/?\\?(.+)(#|$)"),
+			ResolveTestChatTheme,
+		},
 		{
 			qsl("^([^\\?]+)(\\?|#|$)"),
 			HandleUnknown
diff --git a/Telegram/SourceFiles/data/data_cloud_themes.cpp b/Telegram/SourceFiles/data/data_cloud_themes.cpp
index 2ebddb8ce..abe374334 100644
--- a/Telegram/SourceFiles/data/data_cloud_themes.cpp
+++ b/Telegram/SourceFiles/data/data_cloud_themes.cpp
@@ -27,6 +27,8 @@ namespace {
 constexpr auto kFirstReloadTimeout = 10 * crl::time(1000);
 constexpr auto kReloadTimeout = 3600 * crl::time(1000);
 
+bool IsTestingColors/* = false*/;
+
 } // namespace
 
 CloudTheme CloudTheme::Parse(
@@ -395,12 +397,24 @@ std::optional<ChatTheme> CloudThemes::themeForEmoji(
 
 rpl::producer<std::optional<ChatTheme>> CloudThemes::themeForEmojiValue(
 		const QString &emoji) {
+	const auto testing = TestingColors();
 	if (emoji.isEmpty()) {
 		return rpl::single<std::optional<ChatTheme>>(std::nullopt);
 	} else if (auto result = themeForEmoji(emoji)) {
+		if (testing) {
+			return rpl::single(
+				std::move(result)
+			) | rpl::then(chatThemesUpdated(
+			) | rpl::map([=] {
+				return themeForEmoji(emoji);
+			}) | rpl::filter([](const std::optional<ChatTheme> &theme) {
+				return theme.has_value();
+			}));
+		}
 		return rpl::single(std::move(result));
 	}
 	refreshChatThemes();
+	const auto limit = testing ? (1 << 20) : 1;
 	return rpl::single<std::optional<ChatTheme>>(
 		std::nullopt
 	) | rpl::then(chatThemesUpdated(
@@ -408,7 +422,112 @@ rpl::producer<std::optional<ChatTheme>> CloudThemes::themeForEmojiValue(
 		return themeForEmoji(emoji);
 	}) | rpl::filter([](const std::optional<ChatTheme> &theme) {
 		return theme.has_value();
-	}) | rpl::take(1));
+	}) | rpl::take(limit));
+}
+
+bool CloudThemes::TestingColors() {
+	return IsTestingColors;
+}
+
+void CloudThemes::SetTestingColors(bool testing) {
+	IsTestingColors = testing;
+}
+
+QString CloudThemes::PrepareTestingLink(const CloudTheme &theme) {
+	const auto hex = [](int value) {
+		return QChar((value < 10) ? ('0' + value) : ('a' + (value - 10)));
+	};
+	const auto hex2 = [&](int value) {
+		return QString() + hex(value / 16) + hex(value % 16);
+	};
+	const auto color = [&](const QColor &color) {
+		return hex2(color.red()) + hex2(color.green()) + hex2(color.blue());
+	};
+	const auto colors = [&](const std::vector<QColor> &colors) {
+		auto list = QStringList();
+		for (const auto &c : colors) {
+			list.push_back(color(c));
+		}
+		return list.join(",");
+	};
+	auto arguments = QStringList();
+	if (theme.basedOnDark) {
+		arguments.push_back("dark=1");
+	}
+	if (theme.accentColor) {
+		arguments.push_back("accent=" + color(*theme.accentColor));
+	}
+	if (theme.paper && !theme.paper->backgroundColors().empty()) {
+		arguments.push_back("bg=" + colors(theme.paper->backgroundColors()));
+	}
+	if (theme.outgoingAccentColor) {
+		arguments.push_back("out_accent" + color(*theme.outgoingAccentColor));
+	}
+	if (!theme.outgoingMessagesColors.empty()) {
+		arguments.push_back("out_bg=" + colors(theme.outgoingMessagesColors));
+	}
+	return arguments.isEmpty()
+		? QString()
+		: ("tg://test_chat_theme?" + arguments.join("&"));
+}
+
+std::optional<CloudTheme> CloudThemes::updateThemeFromLink(
+		const QString &emoji,
+		const QMap<QString, QString> &params) {
+	if (!TestingColors()) {
+		return std::nullopt;
+	}
+	const auto i = ranges::find(_chatThemes, emoji, &ChatTheme::emoji);
+	if (i == end(_chatThemes)) {
+		return std::nullopt;
+	}
+	const auto hex = [](const QString &value) {
+		return (value.size() != 1)
+			? std::nullopt
+			: (value[0] >= 'a' && value[0] <= 'f')
+			? std::make_optional(10 + int(value[0].unicode() - 'a'))
+			: (value[0] >= '0' && value[0] <= '9')
+			? std::make_optional(int(value[0].unicode() - '0'))
+			: std::nullopt;
+	};
+	const auto hex2 = [&](const QString &value) {
+		const auto first = hex(value.mid(0, 1));
+		const auto second = hex(value.mid(1, 1));
+		return (first && second)
+			? std::make_optional((*first) * 16 + (*second))
+			: std::nullopt;
+	};
+	const auto color = [&](const QString &value) {
+		const auto red = hex2(value.mid(0, 2));
+		const auto green = hex2(value.mid(2, 2));
+		const auto blue = hex2(value.mid(4, 2));
+		return (red && green && blue)
+			? std::make_optional(QColor(*red, *green, *blue))
+			: std::nullopt;
+	};
+	const auto colors = [&](const QString &value) {
+		auto list = value.split(",");
+		auto result = std::vector<QColor>();
+		for (const auto &single : list) {
+			if (const auto c = color(single)) {
+				result.push_back(*c);
+			} else {
+				return std::vector<QColor>();
+			}
+		}
+		return (result.size() > 4) ? std::vector<QColor>() : result;
+	};
+
+	auto &applyTo = params["dark"].isEmpty() ? i->light : i->dark;
+	applyTo.accentColor = color(params["accent"]);
+	const auto bg = colors(params["bg"]);
+	applyTo.paper = (applyTo.paper && !bg.empty())
+		? std::make_optional(applyTo.paper->withBackgroundColors(bg))
+		: std::nullopt;
+	applyTo.outgoingAccentColor = color(params["out_accent"]);
+	applyTo.outgoingMessagesColors = colors(params["out_bg"]);
+	_chatThemesUpdates.fire({});
+	return applyTo;
 }
 
 void CloudThemes::parseChatThemes(const QVector<MTPChatTheme> &list) {
diff --git a/Telegram/SourceFiles/data/data_cloud_themes.h b/Telegram/SourceFiles/data/data_cloud_themes.h
index b684d76a1..22db36461 100644
--- a/Telegram/SourceFiles/data/data_cloud_themes.h
+++ b/Telegram/SourceFiles/data/data_cloud_themes.h
@@ -75,6 +75,13 @@ public:
 	[[nodiscard]] rpl::producer<std::optional<ChatTheme>> themeForEmojiValue(
 		const QString &emoji);
 
+	[[nodiscard]] static bool TestingColors();
+	[[nodiscard]] static void SetTestingColors(bool testing);
+	[[nodiscard]] static QString PrepareTestingLink(const CloudTheme &theme);
+	[[nodiscard]] std::optional<CloudTheme> updateThemeFromLink(
+		const QString &emoji,
+		const QMap<QString, QString> &params);
+
 	void applyUpdate(const MTPTheme &theme);
 
 	void resolve(
diff --git a/Telegram/SourceFiles/history/history_widget.cpp b/Telegram/SourceFiles/history/history_widget.cpp
index 0b748fa60..c6c919693 100644
--- a/Telegram/SourceFiles/history/history_widget.cpp
+++ b/Telegram/SourceFiles/history/history_widget.cpp
@@ -632,6 +632,7 @@ HistoryWidget::HistoryWidget(
 		| PeerUpdateFlag::Slowmode
 		| PeerUpdateFlag::BotStartToken
 		| PeerUpdateFlag::MessagesTTL
+		| PeerUpdateFlag::ChatThemeEmoji
 	) | rpl::filter([=](const Data::PeerUpdate &update) {
 		return (update.peer.get() == _peer);
 	}) | rpl::map([](const Data::PeerUpdate &update) {
@@ -675,6 +676,31 @@ HistoryWidget::HistoryWidget(
 		if (flags & PeerUpdateFlag::MessagesTTL) {
 			checkMessagesTTL();
 		}
+		if ((flags & PeerUpdateFlag::ChatThemeEmoji) && _list) {
+			const auto emoji = _peer->themeEmoji();
+			if (Data::CloudThemes::TestingColors() && !emoji.isEmpty()) {
+				_peer->owner().cloudThemes().themeForEmojiValue(
+					emoji
+				) | rpl::filter_optional(
+				) | rpl::take(
+					1
+				) | rpl::start_with_next([=](const Data::ChatTheme &theme) {
+					auto text = QStringList();
+					const auto push = [&](QString label, const auto &theme) {
+						using namespace Data;
+						const auto l = CloudThemes::PrepareTestingLink(theme);
+						if (!l.isEmpty()) {
+							text.push_back(label + ": " + l);
+						}
+					};
+					push("Light", theme.light);
+					push("Dark", theme.dark);
+					if (!text.isEmpty()) {
+						_field->setText(text.join("\n\n"));
+					}
+				}, _list->lifetime());
+			}
+		}
 	}, lifetime());
 
 	rpl::merge(
diff --git a/Telegram/SourceFiles/settings/settings_codes.cpp b/Telegram/SourceFiles/settings/settings_codes.cpp
index cbfd994d5..3ce089635 100644
--- a/Telegram/SourceFiles/settings/settings_codes.cpp
+++ b/Telegram/SourceFiles/settings/settings_codes.cpp
@@ -12,6 +12,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "mainwidget.h"
 #include "mainwindow.h"
 #include "data/data_session.h"
+#include "data/data_cloud_themes.h"
 #include "main/main_session.h"
 #include "main/main_account.h"
 #include "main/main_domain.h"
@@ -274,6 +275,11 @@ auto GenerateCodes() {
 			});
 		});
 	});
+	codes.emplace(qsl("testchatcolors"), [](SessionController *window) {
+		const auto now = !Data::CloudThemes::TestingColors();
+		Data::CloudThemes::SetTestingColors(now);
+		Ui::Toast::Show(now ? "Testing chat theme colors!" : "Not testing..");
+	});
 
 	return codes;
 }
diff --git a/Telegram/SourceFiles/window/window_session_controller.cpp b/Telegram/SourceFiles/window/window_session_controller.cpp
index 2ce860f41..b4ab89537 100644
--- a/Telegram/SourceFiles/window/window_session_controller.cpp
+++ b/Telegram/SourceFiles/window/window_session_controller.cpp
@@ -1399,13 +1399,14 @@ auto SessionController::cachedChatThemeValue(
 	if (i == end(_customChatThemes)) {
 		cacheChatTheme(data);
 	}
+	const auto limit = Data::CloudThemes::TestingColors() ? (1 << 20) : 1;
 	using namespace rpl::mappers;
 	return rpl::single(
 		_defaultChatTheme
 	) | rpl::then(_cachedThemesStream.events(
 	) | rpl::filter([=](const std::shared_ptr<Ui::ChatTheme> &theme) {
 		return (theme->key() == key);
-	}) | rpl::take(1));
+	}) | rpl::take(limit));
 }
 
 void SessionController::setChatStyleTheme(
@@ -1417,6 +1418,10 @@ void SessionController::setChatStyleTheme(
 	_chatStyle->apply(theme.get());
 }
 
+void SessionController::clearCachedChatThemes() {
+	_customChatThemes.clear();
+}
+
 void SessionController::pushDefaultChatBackground() {
 	const auto background = Theme::Background();
 	const auto &paper = background->paper();
diff --git a/Telegram/SourceFiles/window/window_session_controller.h b/Telegram/SourceFiles/window/window_session_controller.h
index d02bfe851..6904dbded 100644
--- a/Telegram/SourceFiles/window/window_session_controller.h
+++ b/Telegram/SourceFiles/window/window_session_controller.h
@@ -407,6 +407,7 @@ public:
 		const Data::CloudTheme &data)
 	-> rpl::producer<std::shared_ptr<Ui::ChatTheme>>;
 	void setChatStyleTheme(const std::shared_ptr<Ui::ChatTheme> &theme);
+	void clearCachedChatThemes();
 
 	struct PaintContextArgs {
 		not_null<Ui::ChatTheme*> theme;