Magento 1 to Magento 2 migration – SEO data loss and 301 redirects

After migrating from Magento 1 to Magento 2, the shop lost 60% of organic traffic within 2 weeks. Ahrefs showed 4000 404 errors. Old product and category URLs were not being redirected. Fix time: 3 days.

Symptoms

• Drastic drop in organic traffic after migration
• Google Search Console: thousands of 404 errors
• Old Magento 1 URLs (e.g. /catalog/product/view/id/123) return 404
• External links and customer bookmarks stopped working

Diagnosis

# Export all URLs from old M1 database
SELECT request_path, target_path, options
FROM core_url_rewrite
WHERE store_id = 1
INTO OUTFILE '/tmp/m1_urls.csv'
FIELDS TERMINATED BY ','
ENCLOSED BY '"'
LINES TERMINATED BY '
';

Solution

<?php
// Import M1 redirects into M2
$m1Urls = array_map('str_getcsv', file('/tmp/m1_urls.csv'));

foreach ($m1Urls as $row) {
    [$requestPath, $targetPath] = $row;

    $existing = $rewriteCollection
        ->addFieldToFilter('request_path', $requestPath)
        ->getFirstItem();

    if ($existing->getId()) continue;

    $rewrite = $rewriteFactory->create();
    $rewrite->setStoreId(1)
        ->setIdPath('custom_' . md5($requestPath))
        ->setRequestPath($requestPath)
        ->setTargetPath($targetPath)
        ->setRedirectType(301)
        ->setIsSystem(0);

    $rewriteResource->save($rewrite);
}

# Alternative - nginx redirects (faster for large sets)
map $request_uri $new_uri {
    /old-product.html  /new-product.html;
    /old-category/     /new-category/;
}
if ($new_uri) { return 301 $new_uri; }

Takeaways

The SEO migration plan must be part of the migration project – not an afterthought. Before launching M2: export all M1 URLs, generate a redirect map, test every redirect. Monitoring Google Search Console for the first 4 weeks after migration is mandatory.