Tool Comparison · August 2026
Compare SEMrush Site Audit vs. Nebula to Get Verified Audit Results
SEMrush Site Audit finds broken links and crawl errors. Nebula checks which conversion signals your landing page is failing.
Bottom line up front
SEMrush Site Audit is a technical SEO crawler for whole sites - broken links, redirects, crawl errors. Nebula is a conversion audit for a single landing page. SEMrush finds missing alt tags; Nebula finds a headline that does not match the ad. The difference is crawling versus converting.
| Feature | Nebula | SEMrush Site Audit |
|---|---|---|
| Cost | Free audit + $97 repair sprint | SEMrush Pro $139.95/mo (includes Site Audit) |
| Checks conversion criteria | Yes - message match, CTA, trust, above-fold, form friction | No - 130+ technical SEO checks only |
| Technical SEO crawl (broken links, redirects) | No | Yes - core feature with 130+ checks |
| Above-fold analysis | Yes - checks what visitors see without scrolling | No |
| Message-match check | Yes - verifies ad claim matches page headline | No |
| Ad signal detection | Yes - checks page readiness for paid traffic | No - designed for organic SEO health |
| Audience | Founders running paid ads on landing pages | SEO professionals managing site-wide technical health |
| Fix path included | $97 repair sprint - conversion-specific remediation | Issue list with priority scores - no ad/conversion guidance |
Bottom line
SEMrush Site Audit is the right tool for an SEO team fixing crawl errors, thin content, and broken internal links across a large site. If you are running Google or Meta ads to a specific landing page and want to know why it is not converting, SEMrush will tell you the page has a missing alt tag - not that your headline does not match your ad copy. Nebula is built for that diagnosis.
Frequently asked questions
How much does SEMrush cost?
SEMrush Pro starts at $139.95/month and includes Site Audit as one module. Nebula's audit is free with no subscription; the optional repair sprint is a one-time $97.
Does SEMrush check conversions?
No - SEMrush Site Audit runs 130+ technical SEO checks (crawl errors, broken links, metadata, Core Web Vitals) across a whole site. It does not check headline message match, CTA clarity, trust evidence, or above-fold structure on a landing page.
What is a cheap landing page audit alternative to SEMrush?
For a single landing page conversion diagnosis, Nebula is the direct alternative: free instant audit with evidence per finding, plus a $97 one-time fix kit - versus $139.95/month for SEMrush's site-wide technical crawler.
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