diff --git a/docs/cheat-sheet.md b/docs/cheat-sheet.md
index ce53075..642260c 100644
--- a/docs/cheat-sheet.md
+++ b/docs/cheat-sheet.md
@@ -285,6 +285,15 @@ This is an opposite of core `without` filter and adds properties instead of remo
 {{ content|with(['field_image', '#title'], 'Photo'|t) }}
 ```
 
+## Data URI
+The filter generates a URL using the data scheme as defined in [RFC 2397](https://datatracker.ietf.org/doc/html/rfc2397)
+```twig
+{# Inline image. #}
+<img src="{{ '<svg xmlns="http://www.w3.org/2000/svg"><rect width="100" height="50" fill="lime"/></svg>'|data_uri('image/svg+xml') }}" alt="{{ 'Rectangle'|t }}"/>
+{# Image from file system. #}
+<img src="{{ source(directory ~ '/images/logo.svg')|data_uri('image/svg+xml') }}" alt="{{ 'Logo'|t }}"/>
+```
+
 ## Children
 ```twig
 <ul>
diff --git a/src/TwigTweakExtension.php b/src/TwigTweakExtension.php
index cc88132..36e3004 100644
--- a/src/TwigTweakExtension.php
+++ b/src/TwigTweakExtension.php
@@ -110,6 +110,7 @@ class TwigTweakExtension extends AbstractExtension {
       new TwigFilter('truncate', [Unicode::class, 'truncate']),
       new TwigFilter('view', [self::class, 'viewFilter']),
       new TwigFilter('with', [self::class, 'withFilter']),
+      new TwigFilter('data_uri', [self::class, 'dataUriFilter']),
       new TwigFilter('children', [self::class, 'childrenFilter']),
       new TwigFilter('file_uri', [self::class, 'fileUriFilter']),
       new TwigFilter('file_url', [self::class, 'fileUrlFilter']),
@@ -570,6 +571,19 @@ class TwigTweakExtension extends AbstractExtension {
     return $build;
   }
 
+  /**
+   * Creates a data URI (RFC 2397).
+   */
+  public static function dataUriFilter(string $data, string $mime, array $parameters = []): string {
+    $uri = 'data:' . $mime;
+    foreach ($parameters as $key => $value) {
+      $uri .= ';' . $key . '=' . rawurlencode($value);
+    }
+    $uri .= \str_starts_with($data, 'text/') ?
+       ',' . rawurlencode($data) : ';base64,' . base64_encode($data);
+    return $uri;
+  }
+
   /**
    * Adds new element to the array.
    *
diff --git a/tests/src/Functional/TwigTweakTest.php b/tests/src/Functional/TwigTweakTest.php
index 23716cf..a22b4ce 100644
--- a/tests/src/Functional/TwigTweakTest.php
+++ b/tests/src/Functional/TwigTweakTest.php
@@ -342,6 +342,14 @@ final class TwigTweakTest extends BrowserTestBase {
     $xpath = '//div[@class = "tt-with-nested" and text() = "{alpha:{beta:{gamma:456}}}"]';
     $this->assertXpath($xpath);
 
+    // -- Data URI (SVG).
+    $xpath = '//div[@class = "tt-data-uri-svg"]/img[@src = "data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjxyZWN0IHdpZHRoPSIxMDAiIGhlaWdodD0iNTAiIGZpbGw9ImxpbWUiLz48L3N2Zz4="]';
+    $this->assertXpath($xpath);
+
+    // -- Data URI (Iframe).
+    $xpath = '//div[@class = "tt-data-uri-iframe"]/iframe[@src = "data:text/html;charset=UTF-8;base64,PGgxPkhlbGxvIHdvcmxkITwvaDE+"]';
+    $this->assertXpath($xpath);
+
     // -- 'children'.
     $xpath = '//div[@class = "tt-children" and text() = "doremi"]';
     $this->assertXpath($xpath);
diff --git a/tests/twig_tweak_test/templates/twig-tweak-test.html.twig b/tests/twig_tweak_test/templates/twig-tweak-test.html.twig
index 2490f0c..09ae148 100644
--- a/tests/twig_tweak_test/templates/twig-tweak-test.html.twig
+++ b/tests/twig_tweak_test/templates/twig-tweak-test.html.twig
@@ -67,10 +67,16 @@
   <div class="tt-image-style">{{ 'public://images/ocean.jpg'|image_style('thumbnail') }}</div>
   <div class="tt-transliterate">{{ 'Привет!'|transliterate('ru') }}</div>
   <div class="tt-check-markup">{{ '<b>bold</b> <strong>strong</strong>'|check_markup('twig_tweak_test') }}</div>
-  <div class="tt-format-size">{{ 12345|format_size() }}</div>
+  <div class="tt-format-size">{{ 12345|format_size }}</div>
   <div class="tt-truncate">{{ 'Hello world!'|truncate(10, true, true) }}</div>
   <div class="tt-with">{{ {'#markup':'Example'}|with('#prefix', '<b>')|with('#suffix', '</b>') }}</div>
   <div class="tt-with-nested">{{ {alpha: {beta: {gamma: 123}}}|with(['alpha', 'beta', 'gamma'], 456)|json_encode|replace({'"':''}) }}</div>
+  <div class="tt-data-uri-svg">
+    <img src="{{ '<svg xmlns="http://www.w3.org/2000/svg"><rect width="100" height="50" fill="lime"/></svg>'|data_uri('image/svg+xml') }}" alt="{{ 'Rectangle'|t }}" style="height: 50px;"/>
+  </div>
+  <div class="tt-data-uri-iframe">
+    <iframe src="{{ '<h1>Hello world!</h1>'|data_uri('text/html', {charset: 'UTF-8'}) }}"></iframe>
+  </div>
   <div class="tt-children">
     {%-
       set build = {
diff --git a/twig_tweak.api.php b/twig_tweak.api.php
index a920c3d..c2ef429 100644
--- a/twig_tweak.api.php
+++ b/twig_tweak.api.php
@@ -23,6 +23,7 @@ use Twig\TwigTest;
  *   Twig functions to alter.
  */
 function hook_twig_tweak_functions_alter(array &$functions): void {
+  // @phpcs:disable
   // A simple way to implement lazy loaded global variables.
   $callback = static fn (string $name): ?string =>
     match ($name) {
@@ -31,6 +32,7 @@ function hook_twig_tweak_functions_alter(array &$functions): void {
       default => NULL,
     };
   $functions[] = new TwigFunction('var', $callback);
+  // @phpcs:enable
 }
 
 /**