Is the Crawlpit Monster Firefox add-on free?

Yes. It is free, with no account and nothing to configure. Click the toolbar icon and it reports the on-page SEO of the page you are viewing.

Does the add-on work on JavaScript and logged-in pages?

Yes. It reads the page as Firefox renders it, so JavaScript-built content, staging sites, and pages behind a login are all read correctly, which raw-HTML checkers miss.

What data does the Firefox add-on collect?

None. The analysis runs locally in your browser. It reads a tab only when you click the icon, keeps no background process, and sends nothing to a server. Its one request fetches the site's robots.txt to judge indexability.

What does the add-on report?

Title and meta length, the heading outline and H1 count, Open Graph tags, JSON-LD structured data and the declared type, images and missing alt text, internal and external link counts, an indexable verdict, a SERP preview, and a ranked list of issues to fix.

Mozilla Firefox add-on · Free

Crawlpit Monster on-page SEO checker for Mozilla Firefox

Q: How is the add-on different from the Crawlpit Monster desktop app?

The add-on inspects one page. Site-wide checks such as HTTP status, TTFB, redirect chains, duplicate tags, inlinks, and orphan pages come from the Crawlpit Monster desktop app for Mac, which crawls up to 50,000 pages.

Check the on-page SEO of whatever tab you are in, straight from Firefox. Quick On-page SEO Check inspects the fully rendered page, so JavaScript-heavy sites and pages behind a login are read correctly. You get a plain report and a ranked fix list, with nothing to sign up for and nothing leaving your browser.

Add to Firefox See what it reports Free · Private · Works on staging & logged-in pages

What does the Firefox add-on report?

One click reads the page in front of you and lays out every on-page SEO signal, sorted so the issues worth fixing sit at the top. Nothing to open, no dashboard to learn.

Title tag and meta description, each with a live character count
The heading outline, with a flag for missing or repeated H1s
Open Graph tags used when the page is shared
JSON-LD structured data and the content type it declares
A count of images and the exact ones with no alt text
How many internal and external links the page points to
Whether the page is indexable, read from its canonical, meta robots, and robots.txt
A Google search-result preview, plus a ranked list of issues to fix

Reads the page Firefox actually renders

The add-on inspects the rendered DOM rather than the raw source, so single-page apps, content injected by JavaScript, staging builds, and anything gated behind a login are all audited the same way a plain static page would be.

Private, the way Firefox users expect

The whole check runs inside your browser. It looks at a tab only when you click the toolbar button, keeps no background process, and sends nothing to a server. The single request it makes fetches the site's robots.txt to judge indexability. Details are in the privacy policy.

What needs a full site crawl?

A single page can only tell you so much, so anything that depends on seeing the whole site is labelled "not checked here" and belongs in the desktop app. Those site-wide checks are:

HTTP status code
Response time (TTFB)
Redirect chains
Duplicate titles & descriptions
Inlinks
Orphan pages
Crawl depth

When you need the site-wide picture, the free Crawlpit Monster desktop app for Mac crawls up to 50,000 pages. Treat the add-on as the quick look and the app as the deep audit.

Who uses it

It fits anyone who checks pages for a living. SEO specialists auditing a client site, developers verifying a build before release, and editors making sure a new article is set up to rank. Because it reads the live page, it is just as at home on a staging URL or a members-only page as it is on a public one. Prefer Chrome? The same tool ships as the Chrome extension.

Firefox add-on FAQs

Is the Firefox add-on free?

Yes, completely. There is no account, no trial, and nothing to configure. Install it, click the toolbar icon, and you see the on-page SEO of the current page.

Does it handle JavaScript and logged-in pages?

Yes. It works from the page as Firefox renders it, so content added by JavaScript and pages that need a login are read correctly, which raw-HTML checkers usually get wrong.

What data does the add-on collect?

None. The analysis happens locally in Firefox. It reads a tab only when you ask it to, keeps no background process, and transmits nothing. The one exception is fetching the site's robots.txt to work out indexability. See the privacy policy.

How is it different from the Mac app?

The add-on inspects one page at a time. Site-wide checks such as HTTP status, TTFB, redirect chains, duplicate tags, inlinks, and orphan pages come from the desktop app for Mac, which crawls the whole site.

Add the free on-page SEO check to Firefox

One click on any tab breaks down its title, meta, headings, structured data, images, and whether it can be indexed. Free, private, no account.

Add to Firefox Free · Firefox Add-ons