Speed & Core Web Vitals

Find what's slowing you down
and the exact element to fix.

Knowing your LCP is 4.2 seconds doesn't help. Knowing it's your hero image at 890 KB does. SEOMentor pulls real PageSpeed data and connects each metric to what's actually causing it.

Free forever · No credit card required

The gap between a score and a fix

Without SEOMentor

PageSpeed Insights gives you a number and a list of opportunities written for engineers. You learn you have 606 KB of unused JavaScript but not which file, which plugin added it, or whether removing it is safe.

With SEOMentor

You get the same Google data, plus the connection to your actual site the largest image by filename and size, whether you're on WordPress and which theme, and what to change first for the biggest score gain.

Metrics measured

Pulled live from the Google PageSpeed Insights API, for mobile and desktop separately.

LCP — Largest Contentful Paint

How long until the main content appears. The metric that most often fails, usually because of an unoptimised hero image.

INP — Interaction to Next Paint

How quickly the page responds when someone taps or clicks. Usually a JavaScript main-thread problem.

CLS — Cumulative Layout Shift

How much the layout jumps while loading. Typically images or ads without reserved dimensions.

FCP — First Contentful Paint

How long until anything at all renders. A good early indicator of server and render-blocking issues.

TTFB — Time to First Byte

Server response time. Slow TTFB caps every other metric no matter what you optimise on the front end.

Mobile and desktop scores

Scored separately, because a large gap between them points to mobile-specific problems.

One tool, not ten

SEOMentor replaces
your whole SEO stack

Every tool you’d normally juggle audits, rank tracking, backlinks, reporting replaced by one AI that already knows your site.

Product names and logos are trademarks of their respective owners, shown for comparison purposes only. SEOMentor is not affiliated with or endorsed by them.

Powered by the tools
you already trust

Real data from the sources you already use nothing modelled, nothing estimated.

Keywords Everywhere

DataForSEO

PageSpeed Insights

Google Search Console

Google Analytics 4

Claude

Gemini

Keywords Everywhere

DataForSEO

PageSpeed Insights

Google Search Console

Google Analytics 4

Claude

Gemini

Free forever · No credit card required

Product names and logos are trademarks of their respective owners. SEOMentor connects to their official APIs and is not endorsed by them.

How it works

From URL to answer, in three steps

Scan your page

SEOMentor calls the Google PageSpeed Insights API for both mobile and desktop and stores the full result.

See metrics with context

Each vital is colour-coded against Google's thresholds, alongside your image audit so you can see which files are the likely cause.

Ask what to fix first

Mentor AI has the vitals, the opportunities list and your image data together, so it can rank fixes by expected impact rather than listing everything.

What the report tells you

Metrics tied to causes, not just numbers.

LCP 4,231 ms [CRITICAL] — largest element is hero.png at 890 KB, unoptimised, not WebP.

CLS 0.31 [CRITICAL] — layout shift issue, likely images without width and height set.

TTFB 2 ms [OK] — server response is not the bottleneck here.

Desktop 96 vs Mobile 73 — a 23-point gap points to mobile-specific rendering problems.

Real measurement, not estimates

Google PageSpeed Insights

Scores and vitals come directly from Google's API the same source that feeds Search Console's Core Web Vitals report.

Mobile and desktop separately

Both are measured on every scan, because rankings are decided on mobile performance.

Tracked over time

Every scan is stored, so you can re-run after a fix and see exactly how much each metric moved.

Related free tools — no signup

Page Speed Checker Image Alt Checker

Works with

Technical SEO Audit

Every issue, ranked by impact.

Image SEO Audit

Oversized files and missing alt text.

Site Monitoring

Did your last fix work?

All answers to your questions

Where does the Core Web Vitals data come from?

Directly from the Google PageSpeed Insights API. It's the same measurement Google uses, so the numbers match what you see in Search Console's Core Web Vitals report.

Why do my mobile and desktop scores differ so much?

Mobile is measured on a simulated slower device and network. A large gap usually means heavy JavaScript, unoptimised images, or render-blocking resources that a desktop CPU absorbs but a phone doesn't.

Do Core Web Vitals actually affect rankings?

They're a confirmed ranking signal, but a supporting one relevance and content quality matter more. Where vitals bite hardest is user behaviour: slow pages lose visitors before they read anything.

What's a good LCP score?

Google considers under 2.5 seconds good, 2.5 to 4 seconds needs improvement, and above 4 seconds poor. SEOMentor colour-codes against those exact thresholds.

Is this lab data or field data?

PageSpeed Insights returns lab measurements from a controlled test. Field data from real visitors, when Google has enough of it for your site, is visible in Search Console.

How often should I re-check?

After any significant change a new theme, plugin, or image-heavy page. Tracked sites can be re-scanned any time, and the score delta against the previous scan is shown automatically.