Screaming Frog vs Semrush Site Audit

Screaming Frog and Semrush are the two tools I keep coming back to for technical SEO audits. They solve different problems, and they create different problems, and I’ve hit both kinds enough times to have opinions.

The Frog

Screaming Frog is a desktop app. You download it, point it at a URL, and it crawls. For small sites it’s fantastic. First time I ran it on a client’s marketing site, I found broken redirects, missing canonicals, and a 302 chain pointing at some staging server that hadn’t been touched in two years. Twenty minutes in.

The problem is what happens when the site gets big. I had a client with an ecommerce catalog in the low hundreds of thousands of URLs. My laptop fan sounded like it was trying to achieve liftoff. Frog crashes, or it just sits there eating RAM for three hours while you watch the progress bar move like it owes you money. You can configure database storage mode, throw more RAM at it, split the crawl into segments. At some point you have become a sysadmin who occasionally thinks about meta tags.

The other catch is that it only runs where you run it. If you want a scheduled weekly crawl, you need a dedicated machine sitting there doing it. Possible, but annoying.

Semrush Site Audit

Semrush is the other end of the spectrum. Cloud-based, scheduled crawls, dashboard that looks like a product designer actually cared. If you’re already paying for Semrush for keyword research and backlink data, the Site Audit tool is right there.

But Semrush has limits. The crawl caps, the sampling, and the deeper technical checks are weaker than Frog. I worked on a single-page app last year where half the content rendered client-side. Semrush said everything was fine. Running it through Frog with JS rendering on showed console errors on three of the main product pages. Semrush missed them completely.

Every report has a little nudge about upgrading your plan. After a while the audit tool starts to feel like a loss leader for the rest of the suite. If that pattern frustrates you, there are technical SEO crawlers built without crawl quotas or upgrade prompts worth looking at.

Where BSA fits

I’ve been using BSA (Black SEO Analyzer) on a few projects, and it’s the tool I kept wishing existed when Frog was melting my laptop and Semrush was missing things. It runs on your own machine like Frog, with crawl depth and configurability to match, but it writes every page to a local SQLite database as it goes instead of holding the crawl in memory. No desktop memory drama, no nudges to upgrade your plan every time you open a report.

On that same SPA client, BSA rendered the pages in headless Chrome (--spa) and audited the client-side content Semrush never saw. It also flagged a hreflang problem that Frog found but took forty minutes to surface. BSA had it in a readable report in about eight minutes. For a deeper look at exactly where Frog falls short on JavaScript-heavy sites and large catalogs, the crawler built to close those gaps comparison is worth a read.

It’s not perfect. The GUI is newer and there’s no log file integration, so I still join server logs myself. I keep wanting more there. But for running recurring audits on medium and large sites (I schedule the CLI with cron) without paying for a full marketing suite, it’s the tool I reach for now.

What I actually do

For a quick spot check on a small site, I still open Frog. It’s fast and I know the keyboard shortcuts.

For ongoing monitoring on a client retainer, I use BSA. A cron job running the CLI, clean reports, and it doesn’t punish my laptop.

I only use Semrush Site Audit when the client is already on Semrush and doesn’t want another login. Then I cross-check the big stuff with one of the other two.

BSA has a free 14-day trial with no page limit. Point it at a site you already know inside out and see what it finds. That tells you more than any feature comparison chart.

If you’re shopping for a Screaming Frog replacement, run the same audit in BSA. Free 14-day trial — no credit card.

-Sethers