diff --git a/.github/workflows/test-phpcpd.yml b/.github/workflows/test-phpcpd.yml
index 31dcdb232749..f08945514386 100644
--- a/.github/workflows/test-phpcpd.yml
+++ b/.github/workflows/test-phpcpd.yml
@@ -55,4 +55,5 @@ jobs:
             --exclude system/Database/OCI8/Builder.php
             --exclude system/Database/Postgre/Builder.php
             --exclude system/Debug/Exceptions.php
+            --exclude system/HTTP/SiteURI.php
             -- app/ public/ system/
diff --git a/system/HTTP/SiteURI.php b/system/HTTP/SiteURI.php
new file mode 100644
index 000000000000..e64080974940
--- /dev/null
+++ b/system/HTTP/SiteURI.php
@@ -0,0 +1,366 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace CodeIgniter\HTTP;
+
+use BadMethodCallException;
+use CodeIgniter\Exceptions\ConfigException;
+use CodeIgniter\HTTP\Exceptions\HTTPException;
+use Config\App;
+
+/**
+ * URI for the application site
+ */
+class SiteURI extends URI
+{
+    /**
+     * The current baseURL.
+     */
+    private URI $baseURL;
+
+    /**
+     * The path part of baseURL.
+     *
+     * The baseURL "http://example.com/" → '/'
+     * The baseURL "http://localhost:8888/ci431/public/" → '/ci431/public/'
+     */
+    private string $basePathWithoutIndexPage;
+
+    /**
+     * The Index File.
+     */
+    private string $indexPage;
+
+    /**
+     * List of URI segments in baseURL and indexPage.
+     *
+     * If the URI is "http://localhost:8888/ci431/public/index.php/test?a=b",
+     * and the baseURL is "http://localhost:8888/ci431/public/", then:
+     *   $baseSegments = [
+     *       0 => 'ci431',
+     *       1 => 'public',
+     *       2 => 'index.php',
+     *   ];
+     */
+    private array $baseSegments;
+
+    /**
+     * List of URI segments after indexPage.
+     *
+     * The word "URI Segments" originally means only the URI path part relative
+     * to the baseURL.
+     *
+     * If the URI is "http://localhost:8888/ci431/public/index.php/test?a=b",
+     * and the baseURL is "http://localhost:8888/ci431/public/", then:
+     *   $segments = [
+     *       0 => 'test',
+     *   ];
+     *
+     * @var array
+     *
+     * @deprecated This property will be private.
+     */
+    protected $segments;
+
+    /**
+     * URI path relative to baseURL.
+     *
+     * If the baseURL contains sub folders, this value will be different from
+     * the current URI path.
+     *
+     * This value never starts with '/'.
+     */
+    private string $routePath;
+
+    /**
+     * @param string      $relativePath URI path relative to baseURL. May include
+     *                                  queries or fragments.
+     * @param string|null $host         Optional current hostname.
+     * @param string|null $scheme       Optional scheme. 'http' or 'https'.
+     * @phpstan-param 'http'|'https'|null $scheme
+     */
+    public function __construct(
+        App $configApp,
+        string $relativePath = '',
+        ?string $host = null,
+        ?string $scheme = null
+    ) {
+        $this->indexPage = $configApp->indexPage;
+
+        $this->baseURL = $this->determineBaseURL($configApp, $host, $scheme);
+
+        $this->setBasePath();
+
+        // Fix routePath, query, fragment
+        [$routePath, $query, $fragment] = $this->parseRelativePath($relativePath);
+
+        // Fix indexPage and routePath
+        $indexPageRoutePath = $this->getIndexPageRoutePath($routePath);
+
+        // Fix the current URI
+        $uri = $this->baseURL . $indexPageRoutePath;
+
+        // applyParts
+        $parts = parse_url($uri);
+        if ($parts === false) {
+            throw HTTPException::forUnableToParseURI($uri);
+        }
+        $parts['query']    = $query;
+        $parts['fragment'] = $fragment;
+        $this->applyParts($parts);
+
+        $this->setRoutePath($routePath);
+    }
+
+    private function parseRelativePath(string $relativePath): array
+    {
+        $parts = parse_url('http://dummy/' . $relativePath);
+        if ($parts === false) {
+            throw HTTPException::forUnableToParseURI($relativePath);
+        }
+
+        $routePath = $relativePath === '/' ? '/' : ltrim($parts['path'], '/');
+
+        $query    = $parts['query'] ?? '';
+        $fragment = $parts['fragment'] ?? '';
+
+        return [$routePath, $query, $fragment];
+    }
+
+    private function determineBaseURL(
+        App $configApp,
+        ?string $host,
+        ?string $scheme
+    ): URI {
+        $baseURL = $this->normalizeBaseURL($configApp);
+
+        $uri = new URI($baseURL);
+
+        // Update scheme
+        if ($scheme !== null) {
+            $uri->setScheme($scheme);
+        } elseif ($configApp->forceGlobalSecureRequests) {
+            $uri->setScheme('https');
+        }
+
+        // Update host
+        if ($host !== null) {
+            $uri->setHost($host);
+        }
+
+        return $uri;
+    }
+
+    private function getIndexPageRoutePath(string $routePath): string
+    {
+        // Remove starting slash unless it is `/`.
+        if ($routePath !== '' && $routePath[0] === '/' && $routePath !== '/') {
+            $routePath = ltrim($routePath, '/');
+        }
+
+        // Check for an index page
+        $indexPage = '';
+        if ($this->indexPage !== '') {
+            $indexPage = $this->indexPage;
+
+            // Check if we need a separator
+            if ($routePath !== '' && $routePath[0] !== '/' && $routePath[0] !== '?') {
+                $indexPage .= '/';
+            }
+        }
+
+        $indexPageRoutePath = $indexPage . $routePath;
+
+        if ($indexPageRoutePath === '/') {
+            $indexPageRoutePath = '';
+        }
+
+        return $indexPageRoutePath;
+    }
+
+    private function normalizeBaseURL(App $configApp): string
+    {
+        // It's possible the user forgot a trailing slash on their
+        // baseURL, so let's help them out.
+        $baseURL = rtrim($configApp->baseURL, '/ ') . '/';
+
+        // Validate baseURL
+        if (filter_var($baseURL, FILTER_VALIDATE_URL) === false) {
+            throw new ConfigException(
+                'Config\App::$baseURL is invalid.'
+            );
+        }
+
+        return $baseURL;
+    }
+
+    /**
+     * Sets basePathWithoutIndexPage and baseSegments.
+     */
+    private function setBasePath(): void
+    {
+        $this->basePathWithoutIndexPage = $this->baseURL->getPath();
+
+        $this->baseSegments = $this->convertToSegments($this->basePathWithoutIndexPage);
+
+        if ($this->indexPage) {
+            $this->baseSegments[] = $this->indexPage;
+        }
+    }
+
+    /**
+     * @deprecated
+     */
+    public function setBaseURL(string $baseURL): void
+    {
+        throw new BadMethodCallException('Cannot use this method.');
+    }
+
+    /**
+     * @deprecated
+     */
+    public function setURI(?string $uri = null)
+    {
+        throw new BadMethodCallException('Cannot use this method.');
+    }
+
+    /**
+     * Returns the baseURL.
+     *
+     * @interal
+     */
+    public function getBaseURL(): string
+    {
+        return (string) $this->baseURL;
+    }
+
+    /**
+     * Returns the URI path relative to baseURL.
+     *
+     * @return string The Route path.
+     */
+    public function getRoutePath(): string
+    {
+        return $this->routePath;
+    }
+
+    /**
+     * Formats the URI as a string.
+     */
+    public function __toString(): string
+    {
+        return static::createURIString(
+            $this->getScheme(),
+            $this->getAuthority(),
+            $this->getPath(),
+            $this->getQuery(),
+            $this->getFragment()
+        );
+    }
+
+    /**
+     * Sets the route path (and segments).
+     *
+     * @return $this
+     */
+    public function setPath(string $path)
+    {
+        $this->setRoutePath($path);
+
+        return $this;
+    }
+
+    /**
+     * Sets the route path (and segments).
+     */
+    private function setRoutePath(string $routePath): void
+    {
+        $routePath = $this->filterPath($routePath);
+
+        $indexPageRoutePath = $this->getIndexPageRoutePath($routePath);
+
+        $this->path = $this->basePathWithoutIndexPage . $indexPageRoutePath;
+
+        $this->routePath = ltrim($routePath, '/');
+
+        $this->segments = $this->convertToSegments($this->routePath);
+    }
+
+    /**
+     * Converts path to segments
+     */
+    private function convertToSegments(string $path): array
+    {
+        $tempPath = trim($path, '/');
+
+        return ($tempPath === '') ? [] : explode('/', $tempPath);
+    }
+
+    /**
+     * Sets the path portion of the URI based on segments.
+     *
+     * @return $this
+     *
+     * @deprecated This method will be private.
+     */
+    public function refreshPath()
+    {
+        $allSegments = array_merge($this->baseSegments, $this->segments);
+        $this->path  = '/' . $this->filterPath(implode('/', $allSegments));
+
+        if ($this->routePath === '/' && $this->path !== '/') {
+            $this->path .= '/';
+        }
+
+        $this->routePath = $this->filterPath(implode('/', $this->segments));
+
+        return $this;
+    }
+
+    /**
+     * Saves our parts from a parse_url() call.
+     */
+    protected function applyParts(array $parts)
+    {
+        if (! empty($parts['host'])) {
+            $this->host = $parts['host'];
+        }
+        if (! empty($parts['user'])) {
+            $this->user = $parts['user'];
+        }
+        if (isset($parts['path']) && $parts['path'] !== '') {
+            $this->path = $this->filterPath($parts['path']);
+        }
+        if (! empty($parts['query'])) {
+            $this->setQuery($parts['query']);
+        }
+        if (! empty($parts['fragment'])) {
+            $this->fragment = $parts['fragment'];
+        }
+
+        // Scheme
+        if (isset($parts['scheme'])) {
+            $this->setScheme(rtrim($parts['scheme'], ':/'));
+        } else {
+            $this->setScheme('http');
+        }
+
+        // Port
+        if (isset($parts['port']) && $parts['port'] !== null) {
+            // Valid port numbers are enforced by earlier parse_url() or setPort()
+            $this->port = $parts['port'];
+        }
+
+        if (isset($parts['pass'])) {
+            $this->password = $parts['pass'];
+        }
+    }
+}
diff --git a/system/HTTP/URI.php b/system/HTTP/URI.php
index 1e11953051bb..d27598b6bfb1 100644
--- a/system/HTTP/URI.php
+++ b/system/HTTP/URI.php
@@ -14,6 +14,7 @@
 use BadMethodCallException;
 use CodeIgniter\HTTP\Exceptions\HTTPException;
 use Config\App;
+use InvalidArgumentException;
 
 /**
  * Abstraction for a uniform resource identifier (URI).
@@ -34,11 +35,15 @@ class URI
      * Current URI string
      *
      * @var string
+     *
+     * @deprecated Not used.
      */
     protected $uriString;
 
     /**
      * The Current baseURL.
+     *
+     * @deprecated Use SiteURI instead.
      */
     private ?string $baseURL = null;
 
@@ -259,6 +264,8 @@ public function __construct(?string $uri = null)
      * If $silent == true, then will not throw exceptions and will
      * attempt to continue gracefully.
      *
+     * @deprecated 4.4.0 Method not in PSR-7
+     *
      * @return URI
      */
     public function setSilent(bool $silent = true)
@@ -272,6 +279,8 @@ public function setSilent(bool $silent = true)
      * If $raw == true, then will use parseStr() method
      * instead of native parse_str() function.
      *
+     * Note: Method not in PSR-7
+     *
      * @return URI
      */
     public function useRawQueryString(bool $raw = true)
@@ -287,6 +296,8 @@ public function useRawQueryString(bool $raw = true)
      * @return URI
      *
      * @throws HTTPException
+     *
+     * @deprecated This method will be private.
      */
     public function setURI(?string $uri = null)
     {
@@ -404,6 +415,8 @@ public function getUserInfo()
      * Temporarily sets the URI to show a password in userInfo. Will
      * reset itself after the first call to authority().
      *
+     * Note: Method not in PSR-7
+     *
      * @return URI
      */
     public function showPassword(bool $val = true)
@@ -563,6 +576,8 @@ public function getSegment(int $number, string $default = ''): string
      * Set the value of a specific segment of the URI path.
      * Allows to set only existing segments or add new one.
      *
+     * Note: Method not in PSR-7
+     *
      * @param int        $number Segment number starting at 1
      * @param int|string $value
      *
@@ -594,6 +609,8 @@ public function setSegment(int $number, $value)
 
     /**
      * Returns the total number of segments.
+     *
+     * Note: Method not in PSR-7
      */
     public function getTotalSegments(): int
     {
@@ -661,6 +678,8 @@ private function changeSchemeAndPath(string $scheme, string $path): array
     /**
      * Parses the given string and saves the appropriate authority pieces.
      *
+     * Note: Method not in PSR-7
+     *
      * @return $this
      */
     public function setAuthority(string $str)
@@ -690,6 +709,8 @@ public function setAuthority(string $str)
      * @see https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml
      *
      * @return $this
+     *
+     * @deprecated Use `withScheme()` instead.
      */
     public function setScheme(string $str)
     {
@@ -699,6 +720,34 @@ public function setScheme(string $str)
         return $this;
     }
 
+    /**
+     * Return an instance with the specified scheme.
+     *
+     * This method MUST retain the state of the current instance, and return
+     * an instance that contains the specified scheme.
+     *
+     * Implementations MUST support the schemes "http" and "https" case
+     * insensitively, and MAY accommodate other schemes if required.
+     *
+     * An empty scheme is equivalent to removing the scheme.
+     *
+     * @param string $scheme The scheme to use with the new instance.
+     *
+     * @return static A new instance with the specified scheme.
+     *
+     * @throws InvalidArgumentException for invalid or unsupported schemes.
+     */
+    public function withScheme(string $scheme)
+    {
+        $uri = clone $this;
+
+        $scheme = strtolower($scheme);
+
+        $uri->scheme = preg_replace('#:(//)?$#', '', $scheme);
+
+        return $uri;
+    }
+
     /**
      * Sets the userInfo/Authority portion of the URI.
      *
@@ -706,6 +755,8 @@ public function setScheme(string $str)
      * @param string $pass The user's password
      *
      * @return $this
+     *
+     * @TODO PSR-7: Should be `withUserInfo($user, $password = null)`.
      */
     public function setUserInfo(string $user, string $pass)
     {
@@ -719,6 +770,8 @@ public function setUserInfo(string $user, string $pass)
      * Sets the host name to use.
      *
      * @return $this
+     *
+     * @TODO PSR-7: Should be `withHost($host)`.
      */
     public function setHost(string $str)
     {
@@ -733,6 +786,8 @@ public function setHost(string $str)
      * @param int $port
      *
      * @return $this
+     *
+     * @TODO PSR-7: Should be `withPort($port)`.
      */
     public function setPort(?int $port = null)
     {
@@ -757,6 +812,8 @@ public function setPort(?int $port = null)
      * Sets the path portion of the URI.
      *
      * @return $this
+     *
+     * @TODO PSR-7: Should be `withPath($port)`.
      */
     public function setPath(string $path)
     {
@@ -773,6 +830,8 @@ public function setPath(string $path)
      * Sets the current baseURL.
      *
      * @interal
+     *
+     * @deprecated Use SiteURI instead.
      */
     public function setBaseURL(string $baseURL): void
     {
@@ -783,6 +842,8 @@ public function setBaseURL(string $baseURL): void
      * Returns the current baseURL.
      *
      * @interal
+     *
+     * @deprecated Use SiteURI instead.
      */
     public function getBaseURL(): string
     {
@@ -797,6 +858,8 @@ public function getBaseURL(): string
      * Sets the path portion of the URI based on segments.
      *
      * @return $this
+     *
+     * @deprecated This method will be private.
      */
     public function refreshPath()
     {
@@ -814,6 +877,8 @@ public function refreshPath()
      * to clean the various parts of the query keys and values.
      *
      * @return $this
+     *
+     * @TODO PSR-7: Should be `withQuery($query)`.
      */
     public function setQuery(string $query)
     {
@@ -844,6 +909,8 @@ public function setQuery(string $query)
      * portion of the URI.
      *
      * @return URI
+     *
+     * @TODO: PSR-7: Should be `withQueryParams(array $query)`
      */
     public function setQueryArray(array $query)
     {
@@ -855,7 +922,9 @@ public function setQueryArray(array $query)
     /**
      * Adds a single new element to the query vars.
      *
-     * @param int|string $value
+     * Note: Method not in PSR-7
+     *
+     * @param int|string|null $value
      *
      * @return $this
      */
@@ -869,6 +938,8 @@ public function addQuery(string $key, $value = null)
     /**
      * Removes one or more query vars from the URI.
      *
+     * Note: Method not in PSR-7
+     *
      * @param string ...$params
      *
      * @return $this
@@ -886,6 +957,8 @@ public function stripQuery(...$params)
      * Filters the query variables so that only the keys passed in
      * are kept. The rest are removed from the object.
      *
+     * Note: Method not in PSR-7
+     *
      * @param string ...$params
      *
      * @return $this
@@ -913,6 +986,8 @@ public function keepQuery(...$params)
      * @see https://tools.ietf.org/html/rfc3986#section-3.5
      *
      * @return $this
+     *
+     * @TODO PSR-7: Should be `withFragment($fragment)`.
      */
     public function setFragment(string $string)
     {
diff --git a/tests/system/HTTP/SiteURITest.php b/tests/system/HTTP/SiteURITest.php
new file mode 100644
index 000000000000..f2b665b94a38
--- /dev/null
+++ b/tests/system/HTTP/SiteURITest.php
@@ -0,0 +1,492 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace CodeIgniter\HTTP;
+
+use BadMethodCallException;
+use CodeIgniter\Exceptions\ConfigException;
+use CodeIgniter\HTTP\Exceptions\HTTPException;
+use CodeIgniter\Test\CIUnitTestCase;
+use Config\App;
+
+/**
+ * @backupGlobals enabled
+ *
+ * @internal
+ *
+ * @group Others
+ */
+final class SiteURITest extends CIUnitTestCase
+{
+    /**
+     * @dataProvider provideConstructor
+     */
+    public function testConstructor(
+        string $baseURL,
+        string $indexPage,
+        string $relativePath,
+        string $expectedURI,
+        string $expectedRoutePath,
+        string $expectedPath,
+        string $expectedQuery,
+        string $expectedFragment,
+        array $expectedSegments,
+        int $expectedTotalSegments
+    ) {
+        $config            = new App();
+        $config->indexPage = $indexPage;
+        $config->baseURL   = $baseURL;
+
+        $uri = new SiteURI($config, $relativePath);
+
+        $this->assertInstanceOf(SiteURI::class, $uri);
+
+        $this->assertSame($expectedURI, (string) $uri);
+        $this->assertSame($expectedRoutePath, $uri->getRoutePath());
+        $this->assertSame($expectedPath, $uri->getPath());
+        $this->assertSame($expectedQuery, $uri->getQuery());
+        $this->assertSame($expectedFragment, $uri->getFragment());
+        $this->assertSame($baseURL, $uri->getBaseURL());
+
+        $this->assertSame($expectedSegments, $uri->getSegments());
+        $this->assertSame($expectedTotalSegments, $uri->getTotalSegments());
+    }
+
+    public function provideConstructor()
+    {
+        return array_merge($this->provideURIs(), $this->provideRelativePathWithQueryOrFragment());
+    }
+
+    public function provideURIs()
+    {
+        return [
+            '' => [
+                'http://example.com/',          // $baseURL
+                'index.php',                    // $indexPage
+                '',                             // $relativePath
+                'http://example.com/index.php', // $expectedURI
+                '',                             // $expectedRoutePath
+                '/index.php',                   // $expectedPath
+                '',                             // $expectedQuery
+                '',                             // $expectedFragment
+                [],                             // $expectedSegments
+                0,                              // $expectedTotalSegments
+            ],
+            '/' => [
+                'http://example.com/',
+                'index.php',
+                '/',
+                'http://example.com/index.php/',
+                '',
+                '/index.php/',
+                '',
+                '',
+                [],
+                0,
+            ],
+            'one/two' => [
+                'http://example.com/',
+                'index.php',
+                'one/two',
+                'http://example.com/index.php/one/two',
+                'one/two',
+                '/index.php/one/two', '',
+                '',
+                ['one', 'two'],
+                2,
+            ],
+            '/one/two' => [
+                'http://example.com/',
+                'index.php',
+                '/one/two',
+                'http://example.com/index.php/one/two',
+                'one/two',
+                '/index.php/one/two',
+                '',
+                '',
+                ['one', 'two'],
+                2,
+            ],
+            '/one/two/' => [
+                'http://example.com/',
+                'index.php',
+                '/one/two/',
+                'http://example.com/index.php/one/two/',
+                'one/two/',
+                '/index.php/one/two/',
+                '',
+                '',
+                ['one', 'two'],
+                2,
+            ],
+            '//one/two' => [
+                'http://example.com/',
+                'index.php',
+                '//one/two',
+                'http://example.com/index.php/one/two',
+                'one/two',
+                '/index.php/one/two',
+                '',
+                '',
+                ['one', 'two'],
+                2,
+            ],
+            'one/two//' => [
+                'http://example.com/',
+                'index.php',
+                'one/two//',
+                'http://example.com/index.php/one/two/',
+                'one/two/',
+                '/index.php/one/two/',
+                '',
+                '',
+                ['one', 'two'],
+                2,
+            ],
+            '///one///two///' => [
+                'http://example.com/',
+                'index.php',
+                '///one///two///',
+                'http://example.com/index.php/one/two/',
+                'one/two/',
+                '/index.php/one/two/',
+                '',
+                '',
+                ['one', 'two'],
+                2,
+            ],
+            'Subfolder: ' => [
+                'http://example.com/ci4/',
+                'index.php',
+                '',
+                'http://example.com/ci4/index.php',
+                '',
+                '/ci4/index.php',
+                '',
+                '',
+                [],
+                0,
+            ],
+            'Subfolder: one/two' => [
+                'http://example.com/ci4/',
+                'index.php',
+                'one/two',
+                'http://example.com/ci4/index.php/one/two',
+                'one/two',
+                '/ci4/index.php/one/two',
+                '',
+                '',
+                ['one', 'two'],
+                2,
+            ],
+            'EmptyIndexPage: ' => [
+                'http://example.com/',
+                '',
+                '',
+                'http://example.com/',
+                '',
+                '/',
+                '',
+                '',
+                [],
+                0,
+            ],
+            'EmptyIndexPage: /' => [
+                'http://example.com/',
+                '',
+                '/',
+                'http://example.com/',
+                '',
+                '/',
+                '',
+                '',
+                [],
+                0,
+            ],
+        ];
+    }
+
+    public function provideRelativePathWithQueryOrFragment()
+    {
+        return [
+            'one/two?foo=1&bar=2' => [
+                'http://example.com/',                              // $baseURL
+                'index.php',                                        // $indexPage
+                'one/two?foo=1&bar=2',                              // $relativePath
+                'http://example.com/index.php/one/two?foo=1&bar=2', // $expectedURI
+                'one/two',                                          // $expectedRoutePath
+                '/index.php/one/two',                               // $expectedPath
+                'foo=1&bar=2',                                      // $expectedQuery
+                '',                                                 // $expectedFragment
+                ['one', 'two'],                                     // $expectedSegments
+                2,                                                  // $expectedTotalSegments
+            ],
+            'one/two#sec1' => [
+                'http://example.com/',
+                'index.php',
+                'one/two#sec1',
+                'http://example.com/index.php/one/two#sec1',
+                'one/two',
+                '/index.php/one/two',
+                '',
+                'sec1',
+                ['one', 'two'],
+                2,
+            ],
+            'one/two?foo=1&bar=2#sec1' => [
+                'http://example.com/',
+                'index.php',
+                'one/two?foo=1&bar=2#sec1',
+                'http://example.com/index.php/one/two?foo=1&bar=2#sec1',
+                'one/two',
+                '/index.php/one/two',
+                'foo=1&bar=2',
+                'sec1',
+                ['one', 'two'],
+                2,
+            ],
+            'Subfolder: one/two?foo=1&bar=2' => [
+                'http://example.com/ci4/',
+                'index.php',
+                'one/two?foo=1&bar=2',
+                'http://example.com/ci4/index.php/one/two?foo=1&bar=2',
+                'one/two',
+                '/ci4/index.php/one/two',
+                'foo=1&bar=2',
+                '',
+                ['one', 'two'],
+                2,
+            ],
+        ];
+    }
+
+    public function testConstructorHost()
+    {
+        $config                   = new App();
+        $config->allowedHostnames = ['sub.example.com'];
+
+        $uri = new SiteURI($config, '', 'sub.example.com');
+
+        $this->assertInstanceOf(SiteURI::class, $uri);
+        $this->assertSame('http://sub.example.com/index.php', (string) $uri);
+        $this->assertSame('', $uri->getRoutePath());
+        $this->assertSame('/index.php', $uri->getPath());
+        $this->assertSame('http://sub.example.com/', $uri->getBaseURL());
+    }
+
+    public function testConstructorScheme()
+    {
+        $config = new App();
+
+        $uri = new SiteURI($config, '', null, 'https');
+
+        $this->assertInstanceOf(SiteURI::class, $uri);
+        $this->assertSame('https://example.com/index.php', (string) $uri);
+        $this->assertSame('https://example.com/', $uri->getBaseURL());
+    }
+
+    public function testConstructorForceGlobalSecureRequests()
+    {
+        $config                            = new App();
+        $config->forceGlobalSecureRequests = true;
+
+        $uri = new SiteURI($config);
+
+        $this->assertSame('https://example.com/index.php', (string) $uri);
+        $this->assertSame('https://example.com/', $uri->getBaseURL());
+    }
+
+    public function testConstructorInvalidBaseURL()
+    {
+        $this->expectException(ConfigException::class);
+
+        $config          = new App();
+        $config->baseURL = 'invalid';
+
+        new SiteURI($config);
+    }
+
+    /**
+     * @dataProvider provideURIs
+     */
+    public function testSetPath(
+        string $baseURL,
+        string $indexPage,
+        string $relativePath,
+        string $expectedURI,
+        string $expectedRoutePath,
+        string $expectedPath,
+        string $expectedQuery,
+        string $expectedFragment,
+        array $expectedSegments,
+        int $expectedTotalSegments
+    ) {
+        $config            = new App();
+        $config->indexPage = $indexPage;
+        $config->baseURL   = $baseURL;
+
+        $uri = new SiteURI($config);
+
+        $uri->setPath($relativePath);
+
+        $this->assertSame($expectedURI, (string) $uri);
+        $this->assertSame($expectedRoutePath, $uri->getRoutePath());
+        $this->assertSame($expectedPath, $uri->getPath());
+        $this->assertSame($expectedQuery, $uri->getQuery());
+        $this->assertSame($expectedFragment, $uri->getFragment());
+        $this->assertSame($baseURL, $uri->getBaseURL());
+
+        $this->assertSame($expectedSegments, $uri->getSegments());
+        $this->assertSame($expectedTotalSegments, $uri->getTotalSegments());
+    }
+
+    public function testSetSegment()
+    {
+        $config = new App();
+
+        $uri = new SiteURI($config);
+        $uri->setPath('test/method');
+
+        $uri->setSegment(1, 'one');
+
+        $this->assertSame('http://example.com/index.php/one/method', (string) $uri);
+        $this->assertSame('one/method', $uri->getRoutePath());
+        $this->assertSame('/index.php/one/method', $uri->getPath());
+        $this->assertSame(['one', 'method'], $uri->getSegments());
+        $this->assertSame('one', $uri->getSegment(1));
+        $this->assertSame(2, $uri->getTotalSegments());
+    }
+
+    public function testSetSegmentOutOfRange()
+    {
+        $this->expectException(HTTPException::class);
+
+        $config = new App();
+        $uri    = new SiteURI($config);
+        $uri->setPath('test/method');
+
+        $uri->setSegment(4, 'four');
+    }
+
+    public function testSetSegmentSilentOutOfRange()
+    {
+        $config = new App();
+        $uri    = new SiteURI($config);
+        $uri->setPath('one/method');
+        $uri->setSilent();
+
+        $uri->setSegment(4, 'four');
+        $this->assertSame(['one', 'method'], $uri->getSegments());
+    }
+
+    public function testSetSegmentZero()
+    {
+        $this->expectException(HTTPException::class);
+
+        $config = new App();
+        $uri    = new SiteURI($config);
+        $uri->setPath('test/method');
+
+        $uri->setSegment(0, 'four');
+    }
+
+    public function testSetSegmentSubfolder()
+    {
+        $config          = new App();
+        $config->baseURL = 'http://example.com/ci4/';
+
+        $uri = new SiteURI($config);
+        $uri->setPath('test/method');
+
+        $uri->setSegment(1, 'one');
+
+        $this->assertSame('http://example.com/ci4/index.php/one/method', (string) $uri);
+        $this->assertSame('one/method', $uri->getRoutePath());
+        $this->assertSame('/ci4/index.php/one/method', $uri->getPath());
+        $this->assertSame(['one', 'method'], $uri->getSegments());
+        $this->assertSame('one', $uri->getSegment(1));
+        $this->assertSame(2, $uri->getTotalSegments());
+    }
+
+    public function testGetRoutePath()
+    {
+        $config = new App();
+        $uri    = new SiteURI($config);
+
+        $this->assertSame('', $uri->getRoutePath());
+    }
+
+    public function testGetSegments()
+    {
+        $config = new App();
+        $uri    = new SiteURI($config);
+
+        $this->assertSame([], $uri->getSegments());
+    }
+
+    public function testGetSegmentZero()
+    {
+        $this->expectException(HTTPException::class);
+
+        $config = new App();
+        $uri    = new SiteURI($config);
+        $uri->setPath('test/method');
+
+        $uri->getSegment(0);
+    }
+
+    public function testGetSegmentOutOfRange()
+    {
+        $this->expectException(HTTPException::class);
+
+        $config = new App();
+        $uri    = new SiteURI($config);
+        $uri->setPath('test/method');
+
+        $uri->getSegment(4);
+    }
+
+    public function testGetTotalSegments()
+    {
+        $config = new App();
+        $uri    = new SiteURI($config);
+
+        $this->assertSame(0, $uri->getTotalSegments());
+    }
+
+    public function testSetURI()
+    {
+        $this->expectException(BadMethodCallException::class);
+
+        $config = new App();
+        $uri    = new SiteURI($config);
+
+        $uri->setURI('http://another.site.example.jp/');
+    }
+
+    public function testSetBaseURI()
+    {
+        $this->expectException(BadMethodCallException::class);
+
+        $config = new App();
+        $uri    = new SiteURI($config);
+
+        $uri->setBaseURL('http://another.site.example.jp/');
+    }
+
+    public function testGetBaseURL()
+    {
+        $config = new App();
+        $uri    = new SiteURI($config);
+
+        $this->assertSame('http://example.com/', $uri->getBaseURL());
+    }
+}
diff --git a/tests/system/HTTP/URITest.php b/tests/system/HTTP/URITest.php
index fa5caafa1a49..ec3443fdf278 100644
--- a/tests/system/HTTP/URITest.php
+++ b/tests/system/HTTP/URITest.php
@@ -240,6 +240,44 @@ public function testSetSchemeSetsValue()
         $this->assertSame($expected, (string) $uri);
     }
 
+    public function testWithScheme()
+    {
+        $url = 'example.com';
+        $uri = new URI('http://' . $url);
+
+        $new = $uri->withScheme('x');
+
+        $this->assertSame('x://' . $url, (string) $new);
+        $this->assertSame('http://' . $url, (string) $uri);
+    }
+
+    public function testWithSchemeSetsHttps()
+    {
+        $url = 'http://example.com/path';
+        $uri = new URI($url);
+
+        $new = $uri->withScheme('https');
+
+        $this->assertSame('https', $new->getScheme());
+        $this->assertSame('http', $uri->getScheme());
+
+        $expected = 'https://example.com/path';
+        $this->assertSame($expected, (string) $new);
+        $expected = 'http://example.com/path';
+        $this->assertSame($expected, (string) $uri);
+    }
+
+    public function testWithSchemeSetsEmpty()
+    {
+        $url = 'example.com';
+        $uri = new URI('http://' . $url);
+
+        $new = $uri->withScheme('');
+
+        $this->assertSame($url, (string) $new);
+        $this->assertSame('http://' . $url, (string) $uri);
+    }
+
     public function testSetUserInfoSetsValue()
     {
         $url = 'http://example.com/path';
diff --git a/user_guide_src/source/changelogs/v4.4.0.rst b/user_guide_src/source/changelogs/v4.4.0.rst
index 87712aff5bb6..475d08e9eaea 100644
--- a/user_guide_src/source/changelogs/v4.4.0.rst
+++ b/user_guide_src/source/changelogs/v4.4.0.rst
@@ -216,6 +216,9 @@ Deprecations
   ``$tokenName``, ``$headerName``, ``$expires``, ``$regenerate``, and
   ``$redirect`` in ``Security`` are deprecated, and no longer used. Use
   ``$config`` instead.
+- **URI:**
+    - ``URI::setSilent()`` is deprecated.
+    - ``URI::setScheme()`` is deprecated. Use ``withScheme()`` instead.
 
 Bugs Fixed
 **********