TheLinksMaster is now available as a Firefox add-on. It opens as a sidebar on the page you are already viewing and runs 97 checks across indexing, on-page tags, content, images, links, structured data, performance, response headers, site files, rendering and AI visibility.
The workflow is deliberately short: click the toolbar icon or press Ctrl+Shift+U, and the audit runs against the current tab. There is no separate crawl queue, no account and no API key.
Why a sidebar instead of another dashboard
Most SEO tools ask you to paste a URL into a web app and wait for a crawl. That is useful for a full site review, but it is slow when the question is about the page in front of you.
A sidebar keeps the page visible while the checks run. A writer can see whether the primary term reaches the title, H1 and description without leaving the draft. A developer can check a canonical, a noindex directive or a broken JSON-LD block on the staging URL that is already open.
The add-on scores the page across five weighted categories: Technical, Performance, Content, Crawlability and AI visibility. The score is a summary; the individual checks are the useful part.
What the 97 checks cover
The audit looks at indexing status, meta robots, Googlebot directives, X-Robots-Tag, robots.txt rules for the current path, canonical agreement and hreflang syntax.
On-page checks cover title and description by character count and rendered pixel width, heading outline, level jumps, multiple H1s, doctype, charset, lang and viewport. Pixel width matters because a title that fits a character counter can still truncate in a search result.
Content checks include word count, text-to-HTML ratio, Flesch readability, repeated terms and whether the primary term appears in the title, H1 and description. Image checks separate missing alt from empty alt, and look at width and height pairs, lazy loading, format and bytes.
Link checks compare internal and external balance, nofollow coverage, generic anchors, target="_blank" without rel="noopener" and insecure hrefs. Structured data is parsed as JSON-LD, so a broken block is reported as broken rather than counted as markup present.
Performance checks use Navigation Timing from the local browser, plus resource counts, DOM size, render-blocking scripts, compression and caching headers. Site-file checks look at robots.txt, declared sitemaps, lastmod freshness, llms.txt and ads.txt.
The strongest check is raw HTML versus rendered DOM. A server-side crawler often needs a headless browser for that comparison; the local browser already has the rendered page, so the add-on can show what changed after JavaScript ran.
Privacy: local by design
The add-on does not require an account, an API key, telemetry or analytics. It transmits no page content and holds no host permissions, so it can only reach the site already loaded in the tab.
The only outbound action is a navigation the user starts by clicking a link to the website. That link carries the page address as ordinary link text, not as a hidden payload.
For an agency checking a client’s staging site, that local model is easier to explain than a tool that uploads the page to a third-party crawler.
Firefox desktop and Android
The add-on is available on Firefox for desktop and Firefox for Android. The sidebar layout adapts to the smaller screen, which is useful for a quick check while testing a mobile page.
It is not a replacement for a full site crawl. A page-level audit cannot see every orphaned URL, every redirect chain or every internal link graph. It is the fast check before a deeper crawl, not the crawl itself.
Install it
The add-on is listed on Mozilla Add-ons as TheLinksMaster - SEO & AI SEO Toolkit. The TheLinksmaster product page carries the install link and the web app.
For the wider audit workflow, see what TheLinksmaster automates in an SEO audit.
