301 vs 302 Decision Trees for Technical Site Migrations

Context

Selecting the correct HTTP status code dictates crawler behavior, cache control, and link equity transfer. A 301 (Moved Permanently) instructs search engines to replace the old index entry and transfer full PageRank. A 302 (Found) signals temporary routing, preserving the original URL’s indexing and authority. Misalignment fragments index topology and delays equity consolidation. Align your status code selection with the broader URL Mapping & Redirect Architecture to maintain consistent routing across edge and origin layers.

Pre-flight Checks

• Lower legacy domain DNS TTL to 300s at least 48 hours before cutover.
• Maintain active A/CNAME records for the legacy domain throughout the migration window.
• Audit existing internal canonical tags and hreflang attributes.
• Verify zero application-layer redirects are intercepting traffic.
• Prepare a clean legacy-to-destination URL inventory with strict 1:1 matching.
• Validate all destination URLs return 200 OK before mapping.
• Confirm CDN edge configurations allow custom header overrides.

Execution Steps

Evaluate content permanence before assigning status codes. Use 301 for permanent consolidation, URL cleanup, or domain changes. Reserve 302 for A/B testing, seasonal routing, or temporary staging handoffs. Map phased rollout triggers to staging validation, traffic shifting, and canonical handoff milestones. For incremental transitions, consult When to Use 302 Redirects During Phased Migrations to manage temporary routing without fragmenting crawl budgets.

Structure your redirect inventory to prevent soft 404s. Process enterprise-scale mappings through automated pipelines. Standardize data preparation and pre-deployment QA using CSV Mapping Workflows to ensure accurate bulk imports and version control.

Deploy rules at the web server or CDN edge. Prioritize return 301 over rewrite in Nginx to minimize latency. Apply Apache RedirectMatch or mod_rewrite with strict anchor boundaries. Handle legacy path transformations and capture groups safely by referencing Regex Redirect Rules to prevent backtracking and route collisions.

Configs/Commands

Nginx Configuration

server {
 listen 80;
 server_name legacy-domain.com;
 location / {
 return 301 https://target-domain.com$request_uri;
 }
}

Apache Configuration

RewriteEngine On
RewriteCond %{HTTP_HOST} ^legacy-domain\.com$ [NC]
RewriteRule ^(.*)$ https://target-domain.com/$1 [R=301,L]

Cloudflare Page Rules If URL matches *legacy-domain.com/* → Forwarding URL (301) → https://target-domain.com/$1

Validation

Enforce direct path resolution. Every request must resolve in a single hop (301/302 → 200).

• Run headless crawlers to map redirect chains and circular references.
• Execute pre-flight validation to catch mixed status codes before deployment.
• Parse access logs to verify response integrity:

curl -sI -o /dev/null -w '%{http_code} %{redirect_url}' https://legacy-domain.com/test-path
grep -r '301\|302' /var/log/nginx/access.log | awk '{print $7}' | sort | uniq -c | sort -nr
screaming-frog --crawl --redirects-only --export-csv redirect_audit.csv

• Flatten any detected chains by updating the origin rule to point directly to the final destination.
• Preserve query strings using $request_uri or %{QUERY_STRING}.

Rollback Triggers

Browser and CDN cache TTLs dictate rollback feasibility. 301 responses cache aggressively (days to months), while 302s cache temporarily (minutes to hours).

• Monitor post-deployment drift with automated log parsing.
• Set cache invalidation headers (Cache-Control: no-cache or max-age=0) during the initial rollout window.
• If equity transfer stalls or crawl errors spike, revert to the previous routing state immediately.
• Clear edge CDN caches and purge browser caches via Cache-Control headers before reapplying corrected rules.
• Maintain a versioned backup of all pre-migration server configs.

FAQ

Does Google treat 302 redirects as 301s after a certain period? Google may eventually interpret a persistent 302 as permanent, but this is heuristic and unreliable. Relying on this behavior risks index fragmentation. Explicitly use 301 for permanent moves to guarantee predictable equity transfer and canonicalization.

How do I eliminate redirect chains without breaking legacy bookmarks? Audit the chain using log analysis or headless crawlers, then update the origin rule to point directly to the final destination. Preserve query strings using $request_uri or %{QUERY_STRING} variables, and deploy the flattened rule at the edge/CDN layer before origin changes.

Should 301 redirects be implemented at the DNS, CDN, or web server level? DNS cannot issue HTTP redirects; it only resolves IPs. Implement 301s at the CDN edge (e.g., Cloudflare Page Rules, AWS CloudFront Functions) for lowest latency, or at the web server (Nginx/Apache) if CDN routing is unavailable. Avoid application-layer redirects to prevent unnecessary origin processing.

What is the maximum safe number of redirects per URL path? Zero chains. Every request should resolve in a single hop (301/302 → 200). Browsers and crawlers typically cap at 5-10 hops, but any chain degrades Core Web Vitals (LCP, TTFB), wastes crawl budget, and increases the risk of timeout errors during traffic spikes.