If you need to get current URL in Magento 2 PHTML file the easiest way to do this is to use the following code:

$currentUrl = $block->getUrl('*/*/*', ['_current' => true, '_use_rewrite' => true]);

This is the best method since you don't even need to use the Object Manager.

The same code works for block PHP classes as well. But you need to replace $block with $this.

Example:

$currentUrl = $this->getUrl('*/*/*', ['_current' => true, '_use_rewrite' => true]);

But...

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The Best Way to Get Current URL in Magento 2

The best way is to use UrlInterface.

Example:

$urlInterface = \Magento\Framework\App\ObjectManager::getInstance()
    ->get(\Magento\Framework\UrlInterface::class);
$currentUrl = $urlInterface->getCurrentUrl();

Using the object manager directly is not recommended, so you need to include UrlInterface dependence in your class constructor to be able to use it.

Example:

private $urlInterface;

public function __construct(
...
\Magento\Framework\UrlInterface $urlInterface
...
) {
$this->urlInterface = $urlInterface;
}

public function getCurrentUrl()
{
    return $this->urlInterface->getCurrentUrl();
}

Also in some guides, you can find the solution with the store manager:

$storeManager = \Magento\Framework\App\ObjectManager::getInstance()
    ->get(\Magento\Store\Model\StoreManagerInterface::class);
$currentUrl = $storeManager->getStore()->getCurrentUrl();

This method works as well, but it will return the URL with some extra GET parameters ___store and ___from_store, which is not a preferred result, for example:

https://domain.com/some-path?___store=default&___from_store=default

Also if you have a request object you can use its method getUriString to get the current URL.

Example:

$currentUrl = $this->request->getUriString();

And that's how you can get current URL in Magento 2. However, you need a different guide to get the store ID, code, name, or website ID.