SEO Testing & Diagnostics

    SEO Testing & Diagnostics Guide

    How DataJelly Analyzes Your Site for SEO Health and AI-Era Crawl Readiness

    Modern SEO is no longer just about keywords and backlinks — it's about technical clarity, clean structure, machine-readable HTML, and consistent metadata. Search engines and AI crawlers expect predictable, optimized markup that reduces ambiguity and improves indexing speed.

    DataJelly automatically scans your site using the same standards modern search engines expect, identifying structural issues before they cost you rankings or visibility. This guide explains exactly what we test, why it matters, and how DataJelly uses your prerendered snapshots to deliver the most accurate SEO diagnostics possible.

    Overview: How Our SEO Review Works

    Every time DataJelly captures a snapshot, we run your page through a deep technical audit. The system loads the fully rendered HTML (SSR/prerendered) and evaluates:

    Core SEO Tags

    Title, meta description, canonical, viewport, H1, OG/Twitter, robots meta

    Structural HTML Health

    Heading hierarchy, empty DOM, thin content, missing language tags, broken anchors

    Indexing Infrastructure

    robots.txt, sitemap.xml, canonical consistency, hreflang rules

    Content & Accessibility

    Image ALT text, noscript fallbacks, JSON-LD validity, mixed content

    Link-Level Integrity

    Broken internal links, invalid anchors, external link rel-security

    Cross-Page Checks

    Duplicate titles and duplicate meta descriptions across your crawl session

    These tests map directly to ranking factors, crawlability signals, and the requirements AI crawlers use when ingesting HTML for their retrieval pipelines.

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    Why Technical SEO Matters More Than Ever

    Search engines and AI assistants both rely on machine-friendly HTML. When critical tags are missing or malformed, your pages become harder to index, harder to classify, and less likely to appear in search results or AI answers.

    Common symptoms of poor technical SEO include:

    • Slow indexing
    • Missing snippets
    • Incorrect page titles
    • Low mobile rankings
    • Duplicate detection issues
    • Declines in organic traffic

    DataJelly's snapshot-based testing ensures the version of your page that search engines see is the version we test.

    What DataJelly Tests (and Why It Matters)

    All tests below come directly from the logic in SeoReviewService.

    1. Critical Meta Tags & Page Identity

    Title Tag

    Missing or long titles directly impact click-through rate and relevance. We test for:

    • Missing title
    • Title longer than ~60 characters
    • Duplicate titles across your crawl session

    Meta Description

    Required for high-quality snippets. We detect:

    • Missing or empty
    • Duplicate across multiple pages

    Canonical Tag

    Ensures search engines know which URL is the "master" version. We detect:

    • Missing canonical
    • Relative canonical (invalid)
    • Non-HTTPS canonical
    • Cross-domain canonical (dangerous)
    • Multiple canonical tags

    Viewport Tag

    Required for mobile-first indexing and Core Web Vitals. We test for:

    • Missing viewport
    • Missing width=device-width
    • Missing initial-scale

    2. Heading Structure & Semantic Layout

    Search engines map your page into a hierarchy. Missing or incorrect headings cause indexing ambiguity.

    We detect:

    • Missing <h1>
    • Multiple <h1> tags
    • Heading hierarchy jumps (e.g., <h1> → <h3>)
    • Missing <h2> for long-form content

    3. Content Visibility & Render Quality

    DataJelly evaluates the rendered DOM to ensure your content is indexable.

    We detect:

    • Empty DOM (JS-only pages without SSR)
    • Thin content (<150 characters)
    • Placeholder text (e.g., "lorem ipsum")

    These are common SPA issues that prevent indexing entirely.

    4. Crawlability & Indexing Controls

    robots.txt

    We check:

    • If robots.txt exists
    • If it blocks all crawlers
    • If it incorrectly contains "noindex"

    sitemap.xml

    Essential for crawl discovery. We check:

    • If sitemap exists
    • If it is reachable

    Meta Robots

    We detect:

    • noindex
    • nofollow
    • unexpected blocking rules

    5. Social Preview Metadata (OG & Twitter)

    We test for:

    • Missing og:title
    • Missing og:image
    • Invalid or non-HTTPS og:image
    • Missing Twitter card metadata

    These tags improve sharing previews, which impact click-through and brand trust.

    6. Structured Data (JSON-LD)

    We check:

    • Presence of JSON-LD
    • Valid JSON syntax (we parse it)
    • Multiple structured data blocks
    • Malformed schemas

    Search engines use structured data to power:

    • Rich snippets
    • Breadcrumbs
    • FAQ panels
    • Product cards

    7. Links, Navigation & Internal Integrity

    Broken Internal Links

    We simulate bot requests using a DataJelly test user agent to detect:

    • 404 pages
    • 410 pages
    • Over 5 broken links (major issue)

    Invalid Anchors

    We flag:

    • href="#"
    • Empty href
    • javascript: URLs

    External Link Security

    We detect:

    • Missing rel="noopener noreferrer" on _blank links

    8. Image & Media Health

    ALT Text

    Missing ALT attributes hurt accessibility and SEO relevance.

    We check:

    • At least one image has missing or empty ALT
    • We show the offending <img> node

    Mixed Content

    We detect:

    • HTTP images or scripts on HTTPS pages
    • Potential blocking by browsers

    9. Internationalization & Localization

    For global sites, we validate:

    • hreflang attributes
    • Duplicate hreflang values
    • Invalid ISO language codes
    • Missing href on alternate-language tags

    10. HTML, Head, and Layout Quality Checks

    We test for:

    • Missing <html lang>
    • Missing <meta charset>
    • Missing favicon
    • Too many inline scripts in <head>
    • <style> tags inside <body> (performance issue)

    11. SPA & JavaScript Rendering Issues

    Because many crawlers do not execute JavaScript, we check for:

    • Missing <noscript> fallback
    • Empty DOM after script execution
    • Thin text content
    • Mixed or invalid layout/content

    This is especially important for React, Vite, Vue, Angular, and Next-based SPA sites.

    12. Cross-Page Duplicate Detection

    (Unique to DataJelly)

    Across your entire crawl session, we automatically detect:

    • Duplicate titles
    • Duplicate meta descriptions

    This helps avoid:

    • Cannibalization
    • Duplicate clusters
    • Incorrect canonicalization
    • Snapshot-level content conflicts

    No other SPA SEO tool provides this cross-page inspection automatically.

    How DataJelly Turns These Checks into Actionable SEO Insights

    After running the full diagnostic suite, we produce:

    • A detailed issue list
    • Severity scoring (critical / warning / info)
    • Page-level and snapshot-level insights
    • A 0–100 SEO score
    • Clean JSON metadata for dashboards, APIs, and enrichment systems
    • Stored results in Postgres for long-term tracking

    Combined with DataJelly's prerendering engine, this gives you a real view of what Google, Bing, and AI crawlers actually see.

    Why This Is Essential for SPA Sites

    JavaScript-heavy websites often fail SEO audits because crawlers struggle to:

    • Wait for hydration
    • Process client-side rendering
    • Execute third-party scripts
    • Interpret dynamic content
    • Discover routes
    • Build canonical clusters

    DataJelly solves this by:

    • Serving fully-rendered HTML snapshots
    • Detecting SEO problems in the rendered output (not your raw code)
    • Highlighting SPA-specific pitfalls like empty DOM, multiple H1s, and JS-only content
    • Ensuring consistency across your entire crawl session

    Conclusion: Technical SEO Is Foundational SEO

    Search engines reward sites that are:

    Crawlable
    Structurally sound
    Semantically clear
    Fully rendered
    Consistently tagged
    Accessible

    DataJelly's SEO Review Service ensures your site meets these standards automatically — using the same rendered HTML that search engines see, giving you the most accurate and realistic diagnostics possible.

    Ready to Turn Your SPA into a Fully Indexable, AI-Ready Website?

    Just run a crawl — DataJelly handles the rest.

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