SEO testing · Free tool

JavaScript SEO & Rendering Checker.

Find what JavaScript changes, what search engines might miss and what’s stopping pages from rendering correctly. Get clear explanations, visual evidence and fixes your developers can use.

Independent desktop and mobile analysis
Before-and-after screenshots of affected content
Jira-ready fix documents with technical evidence

Free to use. Google Search Console evidence is optional.

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Start with one page. See exactly what JavaScript does.

Website address

Desktop Mobile

Advanced test options

Test clicks and hovers (adds 1–5 min, up to 15 on big sites) Also click links Block known analytics

Stops known tools recording the test, and the report lists them. It can’t stop tracking through the site’s own domain or by its server, and blocking a tag manager can change what the page shows.

Blocked by a firewall? How to allow the audit

01Scan your pageRaw HTML, rendering and interactions

02See the evidencePlain-English findings and screenshots

03Give developers the fixA Jira-ready ticket with acceptance criteria

Built for SEOs and developers

From SEO problem to developer-ready fix.

Understand what’s happening on the page, then pass on the technical evidence needed to resolve it. Both reports use the same findings.

On-screen SEO reportSimple language · Visual evidence

● Confirmed issue · Mobile only

Product description disappears after JavaScript runs

Desktop: content present

Product image

Product description remains visible after rendering.

Mobile: content missing

Product image

Description removed after hydration

What’s happening

The description was in the server HTML but disappeared when the mobile page rendered.

Why it matters

Google primarily uses the mobile version when indexing, so important product information may be lost.

How to fix it

Keep the server-rendered description in place when the client-side code runs.

Jira-ready fix documentTechnical detail · Screenshots

Rendering / hydrationConfirmed issue

SEO: JavaScript replaces the server’s main content (example.com/product)

Affected URLexample.com/productDevicesMobile onlyEvidenceServer HTML, rendered page, screenshots

What

The server HTML contains a product description. It’s missing from the finished mobile page.

Evidence

Server HTML: <div class="description">…</div> After JavaScript: <div class="description"></div>

Acceptance criteria

The main content, main heading and key details in the server HTML are still on the page after JavaScript runs.

▧ With and without JavaScript screenshots

For SEO teamsFindings in plain English with screenshots, Confirmed issue or Indexing risk ratings and practical recommendations.

For developersOne ticket for the page, with each problem’s evidence, fix, source and clear acceptance criteria.

Illustrative example, not a real audit.

Comprehensive, not complicated

Everything you need to understand JavaScript SEO.

Deep technical checks, presented as findings you can understand and act on. Desktop and mobile are analysed independently.

HTML & content changes

Find text, headings, links and key information JavaScript adds, removes, replaces, hides or moves.

Can it be rendered?

Check robots.txt and noindex rules that stop rendering, canonicals changed by JavaScript, non-crawlable links and JavaScript redirects.

Rendering & hydration

Detect JavaScript failures, missing resources, broken HTML heads and content lost during hydration.

Desktop & mobile

See which problems affect one device or both, including mobile-only rendering and navigation defects.

Hidden content & links

Find what only appears after clicks, hovers or scrolling, and whether search engines can discover it.

Evidence & fixes

View screenshots, technical causes where established, Google’s own data and Jira-ready developer recommendations.

View the full technical check list

Content JavaScript changes

Title, meta description, canonical and robots tags before and after JavaScript
Language, text direction, base URL and viewport tags
H1–H6 headings, body text and word count
Links, compared by where they actually go
Images, videos and embedded frames
Open Graph and Twitter cards
Other head tags, meta tags and <noscript> fallbacks
Content replaced in place, with key words, prices and dates lost
Main content moved into the navigation, sidebar or footer
Content hidden with no way to show it, and repeated blocks or H1s

Where content comes from

Readable in the server HTML
Embedded data in the server response
A data request after the page loads
A JavaScript file
Built in the browser, or only in a <noscript> fallback

Can it be crawled and rendered?

robots.txt for this page, for search engines and AI crawlers
noindex added or removed by JavaScript, or sent in the X-Robots-Tag header
nofollow, snippet and preview directives, and data-nosnippet
A canonical changed or duplicated by JavaScript
Head closing early, invalid head markup and SEO tags pushed out of the head
Markup that loses links, headings or images in the parsed page
JavaScript redirects
“Not found” pages that return 200
Links search engines can’t follow
Infinite scroll without crawlable pagination

Rendering and hydration

JavaScript errors
Hydration errors, including silent rebuilds of the server’s content
Failed scripts, styles and data requests
Requests blocked by browser security rules (CSP and CORS)
Files blocked by robots.txt, and a simulated render without them
Streamed sections that never finish, and HTML that’s cut short
Loading placeholders left on the page
Content that disappears or changes during loading
When content and each key SEO signal first appear
Largest content timing
Content that only loads when scrolled
Content inside web components
Images search engines can’t index
Google’s 2 MB limit, for HTML and individual files
Service workers and long-cached JavaScript without fingerprints
Browser features Google’s renderer can’t use
Content that depends on a repeat visit

Clicks and navigation

Content that only appears on click or hover
Each page reached inside the app, refreshed and loaded directly
Whether Back returns to the page

Signals JavaScript breaks

Product data only added by JavaScript
Structured data entities duplicated by JavaScript
Prices, availability, names and FAQ questions that stop matching after JavaScript
Title, H1, canonical and structured data that contradict each other after JavaScript

Google’s own data (separate from the test)

Search Console: index status, last crawl, crawler, Google-selected canonical and rich results
Google’s record compared with this test
Real-visitor LCP, INP and CLS, with trends
Lighthouse performance score and JavaScript costs
Link to Google’s Rich Results Test

In every report

Desktop and mobile tested independently
Confirmed issue, Indexing risk or Informational ratings
Sources for findings, usually Google’s documentation
Screenshots with and without JavaScript
Causes kept separate from coincidences, and held back for A/B variations
Jira ticket, PDF and editable developer report

Find the problem. See the evidence. Give developers the fix.

Run a free JavaScript SEO audit and turn complicated rendering issues into clear, actionable findings.

Run your free audit →