Talk Shop
Home
Learn More
About Us
Follow Us
Blog
Tools
Newsletter
Join Discord
Join

Community

  • Developers
  • Growth
  • Entrepreneurs
  • Support
  • Experts
  • Tools

Location

123 Mars, Crater City, Red Planet

(WiFi may be spotty)

Hours

Who has time for breaks? We're here 24/7!

Contact

hello@letstalkshop.com

Talk Shop
Talk Shop

Built for real builders. Not affiliated with Shopify Inc.

Home
Privacy
Terms
  1. Home
  2. >Blog
  3. >Conversion Optimization
  4. >How to Audit Your Shopify Store for Free: The Complete 2026 Checklist
Conversion Optimization20 min read

How to Audit Your Shopify Store for Free: The Complete 2026 Checklist

A thorough Shopify store audit uncovers the hidden issues killing your conversions, SEO rankings, and page speed. This free checklist covers every audit phase — technical SEO, UX, performance, content, and checkout — using tools that cost nothing.

Talk Shop

Talk Shop

Mar 26, 2026

How to Audit Your Shopify Store for Free: The Complete 2026 Checklist

In this article

  • A Free Shopify Store Audit Can Uncover Thousands of Dollars in Lost Revenue
  • Phase 1: Preparation and Baseline Documentation
  • Phase 2: Technical SEO Audit
  • Phase 3: Page Speed and Performance Audit
  • Phase 4: On-Page SEO and Content Audit
  • Phase 5: Image and Media Audit
  • Phase 6: User Experience and Conversion Audit
  • Phase 7: Checkout and Cart Audit
  • Phase 8: App and Theme Bloat Audit
  • Phase 9: Content and Blog Audit
  • Creating Your Audit Action Plan
  • Free Tools Summary: Your Complete Audit Toolkit

A Free Shopify Store Audit Can Uncover Thousands of Dollars in Lost Revenue

Most Shopify merchants know their store has issues. Pages load slowly on mobile, product descriptions feel thin, checkout abandonment hovers around 70%, and organic traffic has plateaued. What they do not know is which issues matter most — or where to start fixing them.

A structured store audit answers both questions. It systematically examines every layer of your Shopify store — technical SEO, page speed, user experience, content quality, and checkout flow — to identify the specific problems costing you the most revenue. The best part: you can do it entirely with free tools.

If you are wondering how to audit your Shopify store for free, this guide walks through the complete process step by step. You will use Google Search Console, PageSpeed Insights, Lighthouse, Shopify's built-in analytics, and other free resources to run a professional-grade audit without spending a dollar. For a quick automated check, Talk Shop's free SEO audit tool can scan your store across 50+ metrics in minutes — but this manual checklist goes deeper. The conversion optimization resources on our blog cover how to fix the issues you find.

Phase 1: Preparation and Baseline Documentation

Jumping straight into fixes without documenting your starting point is the most common audit mistake. You need baselines to measure whether your changes actually moved the needle.

Gather Your Current Metrics

Before touching anything, record your store's current performance. Open these dashboards and save screenshots or export CSVs:

  1. Shopify Analytics — navigate to Analytics > Dashboards for total sessions, conversion rate, AOV, and revenue over the past 90 days
  2. Google Analytics 4 — check acquisition channels, landing page performance, and engagement rate
  3. Google Search Console — export your top 50 queries by clicks and impressions for the past 3 months
  4. Shopify Speed Report — go to Online Store > Themes and note your current speed score

Create a simple spreadsheet with these columns:

MetricCurrent ValueTargetPriority
Overall conversion rate2.5%+High
Mobile conversion rate1.5%+High
Average page load (mobile)< 3sHigh
Organic sessions/month+20%Medium
Cart abandonment rate< 65%Medium
Bounce rate (homepage)< 45%Medium
Core Web Vitals (LCP)< 2.5sHigh
Core Web Vitals (CLS)< 0.1Medium
Core Web Vitals (INP)< 200msMedium

Set Up Google Search Console (If You Haven't Already)

Google Search Console is the single most valuable free tool for auditing your Shopify store's SEO health. If you have not verified your property yet:

  1. Go to search.google.com/search-console
  2. Add your property using the URL prefix method (enter your full store URL)
  3. Verify ownership using the HTML tag method — paste the meta tag into your Shopify theme's <head> section via Online Store > Themes > Edit Code > theme.liquid
  4. Allow 48-72 hours for initial data to populate

Once verified, Search Console provides free data on index coverage, mobile usability, Core Web Vitals, and keyword performance that would cost hundreds of dollars per month from third-party tools.

Create Your Audit Checklist

Organize your audit into five phases: technical SEO, page speed and performance, on-page SEO and content, user experience and conversion, and checkout optimization. Working through them in this order ensures you fix foundational issues (crawling, indexing, speed) before optimizing higher-level elements (content, UX, checkout).

Phase 2: Technical SEO Audit

A mobile device displaying a product page for technical review.

Technical SEO is the foundation everything else sits on. If Google cannot crawl and index your pages properly, no amount of content optimization will help.

Check Index Coverage

In Google Search Console, navigate to Pages (formerly "Coverage"). This report shows:

  • Indexed pages — pages Google has found and included in search results
  • Not indexed pages — pages Google found but chose not to index (and why)
  • Errors — pages with critical issues preventing indexing

Common Shopify indexing issues include:

  • Duplicate content from product variants — Shopify creates separate URLs for each variant (e.g., /products/shirt?variant=123), which can cause duplicate content flags
  • Collection pagination — paginated collection pages (/collections/all?page=2) sometimes get indexed as separate thin-content pages
  • Tag pages — Shopify auto-generates /collections/vendor-name and /collections/tag-name pages that often contain duplicate content

According to SEOmator's 2026 Shopify SEO audit guide, fixing technical crawl issues should always be your first priority because crawlability problems prevent all other SEO efforts from producing results.

Audit Your Sitemap

Shopify auto-generates a sitemap at yourstore.com/sitemap.xml. Open it in a browser and verify:

  • All important product pages are included
  • All collection pages are included
  • Blog posts are included
  • No broken or redirected URLs appear in the sitemap
  • No pages you intentionally noindexed still appear

Submit your sitemap in Google Search Console under Sitemaps if you haven't already. Check the status — it should show "Success" with a count matching your expected page total.

Check for Broken Links and Redirects

Broken links (404 errors) waste crawl budget and frustrate visitors. Use the free version of Screaming Frog (crawls up to 500 URLs for free — sufficient for most Shopify stores) to identify:

  • 404 errors — pages that no longer exist
  • Redirect chains — URLs that redirect to another redirect (A -> B -> C instead of A -> C)
  • Mixed content — HTTP resources loaded on HTTPS pages
  • Missing canonical tags — pages without a canonical URL specified

For every broken link found, either create a 301 redirect to the most relevant live page or update the source link to point to the correct URL.

IssueSeverityFree Tool to Find ItFix
404 errorsHighScreaming Frog, Search Console301 redirect or fix link
Redirect chainsMediumScreaming FrogShorten to single redirect
Duplicate contentHighSearch Console, Screaming FrogCanonical tags, noindex
Missing sitemap pagesMediumManual sitemap reviewAdd to sitemap or publish
Orphaned pagesLowScreaming FrogAdd internal links

Phase 3: Page Speed and Performance Audit

Page speed directly impacts both conversions and SEO rankings. According to Mastroke's 2026 Shopify store audit research, a one-second delay in page load time can drop conversions by 7%, and even a 0.1-second improvement can measurably increase revenue.

Run Google PageSpeed Insights

Go to pagespeed.web.dev and test these pages in order of priority:

  1. Homepage — your most-visited page
  2. Top collection page — your highest-traffic category
  3. Best-selling product page — your most important conversion page
  4. Cart page — the gateway to checkout

For each page, record both the mobile and desktop scores. Focus on mobile — Google uses mobile-first indexing, meaning your mobile score determines your search rankings.

Target scores:

  • Performance: 70+ (good), 90+ (excellent)
  • Largest Contentful Paint (LCP): under 2.5 seconds
  • Cumulative Layout Shift (CLS): under 0.1
  • Interaction to Next Paint (INP): under 200 milliseconds

Identify Speed Killers

PageSpeed Insights lists specific opportunities to improve speed. The most common Shopify speed issues are:

Unoptimized images — hero images and product photos that are not compressed or served in modern formats (WebP/AVIF). Fix: use Shopify's built-in image optimization (it auto-converts to WebP) and resize images to the maximum display size rather than uploading 4000px originals.

Too many Shopify apps — every installed app injects JavaScript into your theme, even apps you no longer actively use. An audit of your installed apps often reveals 3-5 apps that can be uninstalled or consolidated. Check Settings > Apps and sales channels and remove anything you are not actively using.

Render-blocking JavaScript — third-party scripts (chat widgets, analytics, social proof popups) that block the browser from rendering your page content. Fix: defer non-critical scripts by adding defer or async attributes, or load them after the main content renders.

Excessive Liquid code — complex theme customizations that generate slow server-side rendering. Check your theme's Liquid profiler via yourstore.com/?profile=true (available in development themes) to identify slow-rendering sections.

Run a Lighthouse Audit

Google Lighthouse (built into Chrome DevTools) provides a more detailed performance analysis than PageSpeed Insights alone. Open Chrome DevTools (F12), navigate to the Lighthouse tab, and run an audit with these settings:

  • Device: Mobile
  • Categories: Performance, Accessibility, Best Practices, SEO

Lighthouse generates a report with specific, actionable recommendations ranked by estimated time savings. Focus on the "Opportunities" section first — these are the changes that will produce the largest speed improvements.

The audit will also flag accessibility issues (missing alt text, low contrast ratios, missing form labels) that impact both usability and SEO. For a deeper understanding of how performance connects to rankings, explore our SEO resources.

Phase 4: On-Page SEO and Content Audit

A monitor displaying a performance waterfall chart for speed optimization.

Technical SEO gets your pages indexed. On-page SEO determines where they rank. This phase examines whether your content is optimized for the keywords your customers actually search for.

Audit Title Tags and Meta Descriptions

Open Google Search Console and navigate to Performance. Sort by impressions to see your most-visible queries. For each of your top 20 pages:

  • Title tag — does it include the primary keyword? Is it under 60 characters? Does it compel a click?
  • Meta description — does it summarize the page content? Is it under 155 characters? Does it include a call to action?
  • URL slug — is it short, descriptive, and keyword-rich?

Common Shopify title tag mistakes:

MistakeExampleBetter Version
Too long (truncated in SERPs)"Premium Handcrafted Organic Cotton T-Shirt for Men and Women - All Sizes Available""Organic Cotton T-Shirt - Men & Women
YourBrand"No keyword
"Our Best Product - YourBrand""Organic Cotton T-Shirt - Soft, SustainableYourBrand"
Duplicate across pagesEvery product has "YourBrand Store"Unique title per product with target keyword
Keyword stuffed"T-Shirt Cotton Shirt Tee Cotton T-Shirt Buy"Natural keyword placement, one primary keyword

Check Heading Structure

Every page should have exactly one H1 tag (Shopify handles this automatically with the product or page title) and a logical hierarchy of H2s and H3s. Use Chrome DevTools or the free SEO Meta in 1 Click browser extension to inspect heading structure on your key pages.

Look for:

  • Missing H1 tags (some custom theme sections omit them)
  • Multiple H1 tags on a single page (common when hero banners use H1 styling)
  • Headings that skip levels (H1 directly to H3 with no H2)
  • Headings used for visual styling rather than content structure

Audit Product Descriptions

Thin product descriptions are one of the most common SEO weaknesses on Shopify stores. Google needs at least 300 words of unique content to understand what a page is about and rank it competitively.

For each product page, check:

  • Word count — aim for 300+ words on key products, 150+ on others
  • Unique content — is the description original or copied from the manufacturer?
  • Keyword inclusion — does the description naturally include search terms customers use?
  • Feature/benefit balance — features tell what it is; benefits tell why they should care

Products with manufacturer-copied descriptions compete against every other store selling the same item. Rewriting descriptions in your brand voice with unique angles creates a genuine ranking advantage.

Phase 5: Image and Media Audit

Images account for 40-60% of total page weight on most Shopify stores. Optimizing them is often the single fastest way to improve load times.

Check Image Alt Text

Alt text serves two purposes: accessibility (screen readers describe images to visually impaired visitors) and SEO (Google uses alt text to understand image content). In Shopify admin, navigate to Products and spot-check 20 products for:

  • Missing alt text — images with no alt attribute (bad for accessibility and SEO)
  • Generic alt text — "product image" or "IMG_4532.jpg" (useless for SEO)
  • Keyword-stuffed alt text — "best cheap organic cotton t-shirt buy online free shipping" (penalized by Google)

Good alt text is descriptive and natural: "Light blue organic cotton crew-neck t-shirt on white background."

Audit Image File Sizes

Large, uncompressed images are the most common cause of slow Shopify stores. Use PageSpeed Insights or Lighthouse to identify oversized images, then:

  1. Resize to display dimensions — if an image displays at 800px wide, do not upload a 3000px original
  2. Compress before uploading — use free tools like Squoosh (squoosh.app) or TinyPNG to reduce file sizes by 50-80% without visible quality loss
  3. Use Shopify's image CDN — Shopify automatically serves images from its global CDN and converts to WebP format when the browser supports it

Check for Missing Product Images

Products without images convert at drastically lower rates. Run through your product catalog and flag:

  • Products with no images at all
  • Products with only one image (multiple angles improve conversion by 15-25%)
  • Products where images are low resolution or poorly lit
  • Variant images that are missing (customers want to see each color/size option)

Phase 6: User Experience and Conversion Audit

A monitor displaying an A/B test comparison of different storefront layouts.

This phase shifts focus from search engines to human visitors. A technically perfect store that confuses or frustrates shoppers still fails.

Navigation and Information Architecture

Your store's navigation should get any visitor to any product in 3 clicks or fewer. Test this yourself:

  1. Start on the homepage
  2. Try to find a specific product using only the main navigation
  3. Count clicks — if it takes more than 3, your navigation needs restructuring

Check for these common UX issues:

  • Mega menus that overwhelm — more than 7-8 top-level categories creates decision paralysis
  • Missing search bar — 30% of ecommerce visitors use site search, and they convert at 2-3x higher rates
  • Dead-end pages — collection pages with no products, category pages with no subcategories
  • Inconsistent breadcrumbs — breadcrumb navigation that does not match the actual site hierarchy

Mobile Experience Audit

Over 60% of Shopify traffic arrives on mobile devices, but mobile conversion rates are typically half of desktop rates. According to the Baymard Institute's research on checkout usability, mobile-specific friction is a leading driver of the 70%+ cart abandonment rate in ecommerce.

Test your store on a real phone — not just Chrome DevTools responsive mode, which does not replicate touch interactions, actual network speeds, or device-specific rendering:

  • Tap targets — are buttons and links large enough to tap accurately? (minimum 44x44px)
  • Text readability — can you read product descriptions without pinching to zoom?
  • Image loading — do images load fast enough on a cellular connection?
  • Sticky elements — do sticky headers, chat widgets, or cookie banners overlap important content?
  • Form inputs — do form fields trigger the correct mobile keyboard (numeric for phone numbers, email for email)?

Trust Signals Audit

Trust signals reduce purchase anxiety and directly impact conversion rates across industries. Audit your store for:

  • SSL certificate — the padlock icon should appear on every page (Shopify handles this automatically)
  • Payment badges — Visa, Mastercard, PayPal, Shop Pay logos visible near the Add to Cart button
  • Return policy — clearly linked from product pages, not buried in the footer
  • Contact information — phone number, email, or chat widget accessible from every page
  • Reviews and ratings — social proof on product pages and collection pages
  • Shipping information — delivery timeframes and costs visible before checkout
Trust SignalLocationImpact on Conversion
Payment badgesProduct page, footerReduces payment anxiety
Return policy linkBelow Add to CartLowers purchase risk
Customer reviewsProduct pageProvides social proof
Security badgesCheckout, footerBuilds trust in transaction
Contact infoHeader, footerSignals legitimacy
Shipping detailsProduct pageEliminates surprise costs

Phase 7: Checkout and Cart Audit

The checkout is where revenue is won or lost. According to the Baymard Institute, the average ecommerce checkout still contains 34 usability issues, and better checkout design could improve conversion rates by 35%.

Audit the Add-to-Cart Experience

Complete a test purchase on your own store (use a test order with Shopify's Bogus Gateway or a 100% discount code). Time the journey from product page to order confirmation and note every friction point:

  • Does the Add to Cart button stand out visually? (high contrast, above the fold)
  • Does the cart drawer open immediately after adding, or does it redirect to a separate cart page?
  • Can you see cart contents without leaving the current page?
  • Is the "Continue to Checkout" button prominent and unambiguous?

Check for Surprise Costs

48% of cart abandonment happens because of unexpected costs revealed at checkout. Audit your store for surprise cost issues:

  • Shipping costs — are they shown on the product page or only revealed at checkout?
  • Taxes — does your store show tax-inclusive pricing or add taxes at checkout?
  • Handling fees — are there any hidden fees that appear late in the checkout?

The fix is transparency: show estimated shipping costs on the product page, display tax-inclusive pricing where possible, and use a free shipping threshold ("Free shipping on orders over $50") to reduce abandonment. For deeper cart recovery strategies, our Shopify abandoned cart recovery guide covers email and SMS recovery flows in detail.

Evaluate Checkout Options

Shopify's checkout has improved significantly, but configuration matters. Verify these settings in Settings > Checkout:

  • Guest checkout enabled — forcing account creation causes 24% of checkouts to be abandoned
  • Express checkout options — Shop Pay, Apple Pay, Google Pay, and PayPal Express should all be enabled for one-tap purchasing
  • Autofill compatibility — test that browser autofill correctly populates address and payment fields
  • One-page checkout — Shopify now offers a one-page checkout layout that reduces steps and friction

Audit Post-Purchase Experience

The audit does not end at the confirmation page. Check your post-purchase flow:

  • Order confirmation email — does it arrive within minutes? Is it branded and clear?
  • Shipping notification — does the customer receive tracking information promptly?
  • Review request — is there an automated email asking for a product review 7-14 days after delivery?
  • Cross-sell opportunity — does the confirmation page or email include relevant product recommendations?

Phase 8: App and Theme Bloat Audit

A tablet displaying a visual representation of a checkout process flow.

Shopify apps are the most common hidden cause of slow stores and poor performance scores. Every app you install injects code into your theme — and many leave code behind even after uninstallation.

Audit Installed Apps

Navigate to Settings > Apps and sales channels and review every installed app:

  • Is it actively used? — if you have not opened the app in 30+ days, consider removing it
  • Is it duplicated? — many merchants have 2-3 apps serving the same function (multiple review apps, multiple popup tools, multiple SEO apps)
  • Is it necessary? — some app functions are now built into Shopify natively (basic SEO, product reviews, email marketing)

According to Shopify's SEO checklist for 2026, cleaning up unused apps is one of the highest-impact speed optimizations because it removes unnecessary JavaScript from every page load.

Check for Leftover App Code

Uninstalling an app does not always remove its code from your theme. Open your theme code editor (Online Store > Themes > Edit Code) and search for:

  • <script> tags referencing apps you no longer use
  • Liquid snippets in /snippets/ named after removed apps
  • CSS files or inline styles injected by former apps

Remove any orphaned code carefully — make a backup of your theme first via Actions > Download theme file.

Theme Performance Check

Some Shopify themes are inherently slower than others. Run Lighthouse on your store and compare your performance score against the theme's demo store (most theme developers link to a live demo). If the demo scores significantly higher, the issue is likely your customizations or apps, not the theme itself.

CheckWhere to LookWarning Sign
Unused appsSettings > AppsNot opened in 30+ days
Duplicate functionalityApp list2+ apps doing same job
Leftover app codeTheme editor > snippetsScript tags for removed apps
Theme bloatLighthouse auditDemo scores 20+ points higher
Excessive sectionsTheme customizer15+ sections on homepage

Phase 9: Content and Blog Audit

If your Shopify store has a blog (and it should for organic traffic growth), audit it for quality, SEO optimization, and conversion potential.

Evaluate Existing Blog Posts

For each published blog post, check:

  • Organic traffic — is the post attracting search traffic? (Check Google Analytics or Search Console)
  • Keyword targeting — does the post target a specific keyword with adequate search volume?
  • Content freshness — is the information current, or does it reference outdated data/tools?
  • Internal linking — does the post link to relevant products, collections, or other blog posts?
  • Call to action — does each post guide readers toward a next step (product, collection, email signup)?

Blog posts that generate no traffic after 6 months are candidates for either updating (refresh content, improve keyword targeting) or consolidating (merge thin related posts into one comprehensive guide).

Identify Content Gaps

Compare your blog topics against what your competitors rank for. Use Google Search Console's Performance report to find queries where your store appears on page 2-3 of results — these are "striking distance" keywords where a content update or new dedicated post could push you onto page 1.

Focus on bottom-of-funnel keywords that indicate purchase intent: "best [product type] for [use case]," "how to choose [product type]," and "[product type] vs [product type]" comparisons. These posts attract visitors who are close to making a buying decision, which converts to revenue faster than top-of-funnel informational content.

Creating Your Audit Action Plan

An audit without an action plan is just a list of problems. Prioritize your findings using an impact-effort matrix that ranks every issue by revenue impact (high, medium, low) and implementation effort (easy, moderate, hard).

Priority Framework

Fix issues in this order:

  1. High impact, easy effort — these are your quick wins. Examples: enabling guest checkout, adding payment badges, compressing oversized images, removing unused apps
  2. High impact, moderate effort — schedule these for the next 2-4 weeks. Examples: rewriting product descriptions, fixing mobile UX issues, optimizing checkout flow
  3. Medium impact, easy effort — batch these into a single sprint. Examples: fixing alt text, updating meta descriptions, adding internal links
  4. High impact, hard effort — plan these as projects. Examples: theme migration, headless architecture, full content strategy overhaul

Set Up Ongoing Monitoring

A one-time audit catches current issues, but stores degrade over time as new apps are installed, content is added, and Shopify platform updates change behavior. Set a recurring quarterly audit schedule:

  • Monthly: Check Core Web Vitals in Search Console, review speed scores, scan for new 404 errors
  • Quarterly: Full audit using this checklist, compare metrics against your baselines
  • Annually: Evaluate theme performance, review app stack holistically, assess content strategy

Use Talk Shop's ecommerce tools for quick automated checks between manual audits, and follow our Shopify conversion rate optimization tips to implement the fixes that move the needle most.

Free Tools Summary: Your Complete Audit Toolkit

Every tool mentioned in this audit guide is free. Here is the complete list organized by audit phase:

ToolPhaseWhat It DoesURL
Google Search ConsoleTechnical SEOIndex coverage, keyword performance, mobile usabilitysearch.google.com/search-console
Google PageSpeed InsightsSpeedCore Web Vitals, speed scores, optimization suggestionspagespeed.web.dev
Google LighthouseSpeed, AccessibilityDetailed performance audit, accessibility checksBuilt into Chrome DevTools
Screaming Frog (free tier)Technical SEOCrawl up to 500 URLs, find broken links, redirectsscreamingfrog.co.uk
Shopify AnalyticsConversionSessions, conversion funnels, AOV, revenueBuilt into Shopify admin
Shopify Speed ReportSpeedTheme speed score and trendsOnline Store > Themes
Google Analytics 4All phasesTraffic sources, user behavior, engagementanalytics.google.com
Talk Shop SEO AuditAll phasesAutomated 50+ metric scanletstalkshop.com/ecommerce-tools/seo-audit

According to Promodo's Shopify SEO audit checklist, the tools listed above cover 90%+ of what paid enterprise SEO platforms offer for Shopify stores. The difference between a free audit and a paid one is not the tools — it is the expertise applied to interpreting the results and prioritizing the fixes.

You now have everything you need to audit your Shopify store for free — thoroughly, systematically, and with clear next steps. The merchants in the Talk Shop community regularly share their audit results and help each other prioritize fixes. Start your audit today, and check our guide on how to get sales on Shopify for strategies to convert the traffic your optimizations unlock.

What was the most surprising issue you found when auditing your Shopify store? Share your findings below.

Conversion OptimizationSEOAnalytics & Data
Talk Shop

About Talk Shop

The Talk Shop team — insights from our community of Shopify developers, merchants, and experts.

Related Insights

Related

Best Shopify SEO Apps: 10 Tools Ranked for 2026

Related

Shopify About Us Page Examples: 15 Pages That Build Trust and Convert

The ecommerce newsletter that's actually useful.

Daily trends, teardowns, and tactics from the top 1% of ecommerce brands. Delivered every morning.

No spam. Unsubscribe anytime. · Learn more

Free

SEO Audit Tool

Analyze your store's SEO in seconds. Get a scored report with actionable fixes.

Audit Your Site

Talk Shop Daily

Daily ecommerce news, teardowns, and tactics.

No spam. Unsubscribe anytime. · Learn more

Try our Free SEO Audit