diff --git a/internal/app/app.go b/internal/app/app.go
index 936bba61..448d52e1 100644
--- a/internal/app/app.go
+++ b/internal/app/app.go
@@ -15,6 +15,7 @@ import (
 	"github.com/anfragment/zen/internal/certstore"
 	"github.com/anfragment/zen/internal/cfg"
 	"github.com/anfragment/zen/internal/cosmetic"
+	"github.com/anfragment/zen/internal/cssrule"
 	"github.com/anfragment/zen/internal/filter"
 	"github.com/anfragment/zen/internal/jsrule"
 	"github.com/anfragment/zen/internal/logger"
@@ -174,9 +175,10 @@ func (a *App) StartProxy() (err error) {
 	}
 
 	cosmeticRulesInjector := cosmetic.NewInjector()
+	cssRulesInjector := cssrule.NewInjector()
 	jsRuleInjector := jsrule.NewInjector()
 
-	filter, err := filter.NewFilter(a.config, ruleMatcher, exceptionRuleMatcher, scriptletInjector, cosmeticRulesInjector, jsRuleInjector, a.eventsHandler)
+	filter, err := filter.NewFilter(a.config, ruleMatcher, exceptionRuleMatcher, scriptletInjector, cosmeticRulesInjector, cssRulesInjector, jsRuleInjector, a.eventsHandler)
 	if err != nil {
 		return fmt.Errorf("create filter: %v", err)
 	}
diff --git a/internal/cssrule/injector.go b/internal/cssrule/injector.go
new file mode 100644
index 00000000..2fc4895d
--- /dev/null
+++ b/internal/cssrule/injector.go
@@ -0,0 +1,78 @@
+package cssrule
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"log"
+	"net/http"
+	"regexp"
+	"strings"
+
+	"github.com/anfragment/zen/internal/hostmatch"
+	"github.com/anfragment/zen/internal/htmlrewrite"
+	"github.com/anfragment/zen/internal/logger"
+)
+
+var (
+	RuleRegex          = regexp.MustCompile(`.*#@?\$#.+`)
+	primaryRuleRegex   = regexp.MustCompile(`(.*?)#\$#(.*)`)
+	exceptionRuleRegex = regexp.MustCompile(`(.*?)#@\$#(.+)`)
+
+	injectionStart = []byte("<style>")
+	injectionEnd   = []byte("</style>")
+)
+
+type store interface {
+	AddPrimaryRule(hostnamePatterns string, css string) error
+	AddExceptionRule(hostnamePatterns string, css string) error
+	Get(hostname string) []string
+}
+
+type Injector struct {
+	store store
+}
+
+func NewInjector() *Injector {
+	return &Injector{
+		store: hostmatch.NewHostMatcher[string](),
+	}
+}
+
+func (inj *Injector) AddRule(rule string) error {
+	if match := primaryRuleRegex.FindStringSubmatch(rule); match != nil {
+		if err := inj.store.AddPrimaryRule(match[1], match[2]); err != nil {
+			return fmt.Errorf("add primary rule: %w", err)
+		}
+		return nil
+	}
+
+	if match := exceptionRuleRegex.FindStringSubmatch(rule); match != nil {
+		if err := inj.store.AddExceptionRule(match[1], match[2]); err != nil {
+			return fmt.Errorf("add exception rule: %w", err)
+		}
+		return nil
+	}
+
+	return errors.New("unsupported syntax")
+}
+
+func (inj *Injector) Inject(req *http.Request, res *http.Response) error {
+	hostname := req.URL.Hostname()
+	cssRules := inj.store.Get(hostname)
+	log.Printf("got %d css rules for %q", len(cssRules), logger.Redacted(hostname))
+	if len(cssRules) == 0 {
+		return nil
+	}
+
+	var ruleInjection bytes.Buffer
+	ruleInjection.Write(injectionStart)
+	ruleInjection.WriteString(strings.Join(cssRules, ""))
+	ruleInjection.Write(injectionEnd)
+
+	htmlrewrite.ReplaceHeadContents(res, func(match []byte) []byte {
+		return bytes.Join([][]byte{match, ruleInjection.Bytes()}, nil)
+	})
+
+	return nil
+}
diff --git a/internal/filter/filter.go b/internal/filter/filter.go
index 57390135..1dab6a98 100644
--- a/internal/filter/filter.go
+++ b/internal/filter/filter.go
@@ -16,6 +16,7 @@ import (
 
 	"github.com/anfragment/zen/internal/cfg"
 	"github.com/anfragment/zen/internal/cosmetic"
+	"github.com/anfragment/zen/internal/cssrule"
 	"github.com/anfragment/zen/internal/jsrule"
 	"github.com/anfragment/zen/internal/logger"
 	"github.com/anfragment/zen/internal/rule"
@@ -52,6 +53,11 @@ type cosmeticRulesInjector interface {
 	AddRule(string) error
 }
 
+type cssRulesInjector interface {
+	Inject(*http.Request, *http.Response) error
+	AddRule(string) error
+}
+
 type jsRuleInjector interface {
 	AddRule(rule string) error
 	Inject(*http.Request, *http.Response) error
@@ -66,6 +72,7 @@ type Filter struct {
 	exceptionRuleMatcher  ruleMatcher
 	scriptletsInjector    scriptletsInjector
 	cosmeticRulesInjector cosmeticRulesInjector
+	cssRulesInjector      cssRulesInjector
 	jsRuleInjector        jsRuleInjector
 	eventsEmitter         filterEventsEmitter
 }
@@ -80,7 +87,7 @@ var (
 )
 
 // NewFilter creates and initializes a new filter.
-func NewFilter(config config, ruleMatcher ruleMatcher, exceptionRuleMatcher ruleMatcher, scriptletsInjector scriptletsInjector, cosmeticRulesInjector cosmeticRulesInjector, jsRuleInjector jsRuleInjector, eventsEmitter filterEventsEmitter) (*Filter, error) {
+func NewFilter(config config, ruleMatcher ruleMatcher, exceptionRuleMatcher ruleMatcher, scriptletsInjector scriptletsInjector, cosmeticRulesInjector cosmeticRulesInjector, cssRulesInjector cssRulesInjector, jsRuleInjector jsRuleInjector, eventsEmitter filterEventsEmitter) (*Filter, error) {
 	if config == nil {
 		return nil, errors.New("config is nil")
 	}
@@ -96,6 +103,9 @@ func NewFilter(config config, ruleMatcher ruleMatcher, exceptionRuleMatcher rule
 	if cosmeticRulesInjector == nil {
 		return nil, errors.New("cosmeticRulesInjector is nil")
 	}
+	if cssRulesInjector == nil {
+		return nil, errors.New("cssRulesInjector is nil")
+	}
 	if jsRuleInjector == nil {
 		return nil, errors.New("jsRuleInjector is nil")
 	}
@@ -109,6 +119,7 @@ func NewFilter(config config, ruleMatcher ruleMatcher, exceptionRuleMatcher rule
 		exceptionRuleMatcher:  exceptionRuleMatcher,
 		scriptletsInjector:    scriptletsInjector,
 		cosmeticRulesInjector: cosmeticRulesInjector,
+		cssRulesInjector:      cssRulesInjector,
 		jsRuleInjector:        jsRuleInjector,
 		eventsEmitter:         eventsEmitter,
 	}
@@ -195,6 +206,13 @@ func (f *Filter) AddRule(rule string, filterListName *string, filterListTrusted
 		}
 	}
 
+	if filterListTrusted && cssrule.RuleRegex.MatchString(rule) {
+		if err := f.cssRulesInjector.AddRule(rule); err != nil {
+			return false, fmt.Errorf("add css rule: %w", err)
+		}
+		return false, nil
+	}
+
 	if filterListTrusted && jsrule.RuleRegex.MatchString(rule) {
 		if err := f.jsRuleInjector.AddRule(rule); err != nil {
 			return false, fmt.Errorf("add js rule: %w", err)
@@ -268,6 +286,9 @@ func (f *Filter) HandleResponse(req *http.Request, res *http.Response) error {
 		if err := f.cosmeticRulesInjector.Inject(req, res); err != nil {
 			log.Printf("error injecting cosmetic rules for %q: %v", logger.Redacted(req.URL), err)
 		}
+		if err := f.cssRulesInjector.Inject(req, res); err != nil {
+			log.Printf("error injecting css rules for %q: %v", logger.Redacted(req.URL), err)
+		}
 		if err := f.jsRuleInjector.Inject(req, res); err != nil {
 			// The error is recoverable, so we log it and continue processing the response.
 			log.Printf("error injecting js rules for %q: %v", logger.Redacted(req.URL), err)