diff --git a/CHANGELOG.md b/CHANGELOG.md
index d1a261b4..b02c8ebf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 
 ### Deprecated
 
+- Deprecate `__toString()` (#1006)
 - Deprecate greedy calculation of selector specificity (#1018)
 - Deprecate the IE hack in `Rule` (#993, #1003)
 - `OutputFormat` properties for space around list separators as an array (#880)
diff --git a/src/CSSList/AtRuleBlockList.php b/src/CSSList/AtRuleBlockList.php
index 5930b932..a424adbe 100644
--- a/src/CSSList/AtRuleBlockList.php
+++ b/src/CSSList/AtRuleBlockList.php
@@ -50,6 +50,8 @@ public function atRuleArgs()
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/CSSList/CSSList.php b/src/CSSList/CSSList.php
index 5b8f41d5..0f40d40a 100644
--- a/src/CSSList/CSSList.php
+++ b/src/CSSList/CSSList.php
@@ -416,6 +416,8 @@ public function removeDeclarationBlockBySelector($mSelector, $bRemoveAll = false
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/CSSList/KeyFrame.php b/src/CSSList/KeyFrame.php
index 69e2e4d9..618308a7 100644
--- a/src/CSSList/KeyFrame.php
+++ b/src/CSSList/KeyFrame.php
@@ -61,6 +61,8 @@ public function getAnimationName()
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Comment/Comment.php b/src/Comment/Comment.php
index 8c02f3de..1d8810ec 100644
--- a/src/Comment/Comment.php
+++ b/src/Comment/Comment.php
@@ -59,6 +59,8 @@ public function setComment($sComment)
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Property/CSSNamespace.php b/src/Property/CSSNamespace.php
index f39c2877..0d90cc3b 100644
--- a/src/Property/CSSNamespace.php
+++ b/src/Property/CSSNamespace.php
@@ -55,6 +55,8 @@ public function getLineNo()
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Property/Charset.php b/src/Property/Charset.php
index 5e25bd4e..de9016ad 100644
--- a/src/Property/Charset.php
+++ b/src/Property/Charset.php
@@ -75,6 +75,8 @@ public function getCharset()
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Property/Import.php b/src/Property/Import.php
index 9b40e304..e3f10474 100644
--- a/src/Property/Import.php
+++ b/src/Property/Import.php
@@ -76,6 +76,8 @@ public function getLocation()
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Property/Selector.php b/src/Property/Selector.php
index dd7bd880..a0611688 100644
--- a/src/Property/Selector.php
+++ b/src/Property/Selector.php
@@ -121,6 +121,8 @@ public function setSelector($sSelector)
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Renderable.php b/src/Renderable.php
index d7c6aba6..1f1b475d 100644
--- a/src/Renderable.php
+++ b/src/Renderable.php
@@ -6,6 +6,8 @@ interface Renderable
 {
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString();
 
diff --git a/src/Rule/Rule.php b/src/Rule/Rule.php
index f6e291fb..984071c0 100644
--- a/src/Rule/Rule.php
+++ b/src/Rule/Rule.php
@@ -359,6 +359,8 @@ public function getIsImportant()
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/RuleSet/AtRuleSet.php b/src/RuleSet/AtRuleSet.php
index 93fd07af..e687cb96 100644
--- a/src/RuleSet/AtRuleSet.php
+++ b/src/RuleSet/AtRuleSet.php
@@ -53,6 +53,8 @@ public function atRuleArgs()
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/RuleSet/DeclarationBlock.php b/src/RuleSet/DeclarationBlock.php
index 60d0b0c4..3b6c8775 100644
--- a/src/RuleSet/DeclarationBlock.php
+++ b/src/RuleSet/DeclarationBlock.php
@@ -831,6 +831,8 @@ public function createFontShorthand()
      * @return string
      *
      * @throws OutputException
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/RuleSet/RuleSet.php b/src/RuleSet/RuleSet.php
index 0cf7ac95..bc87856b 100644
--- a/src/RuleSet/RuleSet.php
+++ b/src/RuleSet/RuleSet.php
@@ -268,6 +268,8 @@ public function removeRule($mRule)
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Value/CSSFunction.php b/src/Value/CSSFunction.php
index de8e558f..fcf641d5 100644
--- a/src/Value/CSSFunction.php
+++ b/src/Value/CSSFunction.php
@@ -88,6 +88,8 @@ public function getArguments()
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Value/CSSString.php b/src/Value/CSSString.php
index 0251dc7c..a6a705b5 100644
--- a/src/Value/CSSString.php
+++ b/src/Value/CSSString.php
@@ -94,6 +94,8 @@ public function getString()
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Value/Color.php b/src/Value/Color.php
index fbbf11a1..d4b7caf0 100644
--- a/src/Value/Color.php
+++ b/src/Value/Color.php
@@ -155,6 +155,8 @@ public function getColorDescription()
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Value/LineName.php b/src/Value/LineName.php
index 5b59fce5..effc827c 100644
--- a/src/Value/LineName.php
+++ b/src/Value/LineName.php
@@ -51,6 +51,8 @@ public static function parse(ParserState $oParserState)
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Value/Size.php b/src/Value/Size.php
index 2e45d272..98876973 100644
--- a/src/Value/Size.php
+++ b/src/Value/Size.php
@@ -222,6 +222,8 @@ public function isRelative()
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Value/URL.php b/src/Value/URL.php
index 7d5bd8e8..1f2a0af7 100644
--- a/src/Value/URL.php
+++ b/src/Value/URL.php
@@ -81,6 +81,8 @@ public function getURL()
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {
diff --git a/src/Value/ValueList.php b/src/Value/ValueList.php
index 9ae3da99..61962258 100644
--- a/src/Value/ValueList.php
+++ b/src/Value/ValueList.php
@@ -90,6 +90,8 @@ public function setListSeparator($sSeparator)
 
     /**
      * @return string
+     *
+     * @deprecated in V8.8.0, will be removed in V9.0.0. Use `render` instead.
      */
     public function __toString()
     {