PageSpeed Insights: a beginner's guide
Lighthouse audit via Google PageSpeed
Page speed: what makes a website feel fast (and why Google cares)
Page speed is the umbrella term for how long a web page takes to load, become interactive, and feel responsive to a real human user. It is not a single number — it is a small constellation of measurements, each one capturing a slightly different part of "how does this page feel?" Some of those measurements happen in the first second after you click a link (how long until you see something on the screen?). Some happen later in the load (how long until you can actually scroll without the page jumping around?). And some happen the moment you try to interact (how long does the button take to respond when you tap it?).
You should care because page speed is the single biggest invisible reason a website loses customers. Slow pages don't usually fail in dramatic ways — they fail by silently making people leave before they ever see your content. Google has measured this in detail and the curves are unforgiving: when a mobile page goes from 1 second to 3 seconds to load, the probability of a visitor bouncing increases by 32%. From 1 to 5 seconds, by 90%. From 1 to 10 seconds, by 123%. Every fraction of a second is a fraction of a customer.
The five things every page-speed measurement actually looks at:
Time to first byte (TTFB) — how long the server takes to send the very first byte of the response after a click. Good is under 600 milliseconds.
Largest Contentful Paint (LCP) — how long until the biggest visible thing on the page (usually the hero image or a headline) actually appears. Google's official threshold for "good" is under 2.5 seconds.
Cumulative Layout Shift (CLS) — how much the page jumps around as it loads. Have you ever tried to tap a button and then a banner ad popped in and you tapped the wrong thing? That is a layout shift. The Google threshold is a CLS score under 0.1.
Interaction to Next Paint (INP) — how long the page takes to respond after you actually do something (tap, click, type). Good is under 200 milliseconds.
Total page weight — how many bytes the page downloads to render. Modern pages routinely cross 5 MB; the fastest pages stay under 1 MB.
Three questions a page-speed check answers:
Is my website actually slow, or does it just feel slow on my fast connection?
Which specific change would give me the biggest speed boost for the least work?
Am I losing visitors and search rankings because of performance problems I cannot see from my office laptop?
The cost of ignoring page speed is the slow, invisible erosion of traffic and conversions over months. The fix is rarely a complete rebuild — it is almost always a handful of small wins (compress images, lazy-load below-the-fold assets, set the right cache headers, use a CDN) that compound into a noticeably faster experience. The first step is measuring what you actually have, which is exactly what a page-speed audit gives you.
The PageSpeed Insights endpoint, in plain language
In one sentence: Lighthouse audit via Google PageSpeed
Runs a Lighthouse audit via the Google PageSpeed Insights API (Application Programming Interface). Returns performance, accessibility, best-practices, and SEO (Search Engine Optimization) scores, plus top optimization opportunities and diagnostics.
Don't worry if some of the words above are still unfamiliar — there's a plain-language glossary at the bottom of this page, and most of the terms link to their own beginner guides if you want to learn more.
What is actually happening when you call it
Here's what's actually happening behind the scenes when you call this endpoint:
Submits the domain to Google PageSpeed Insights API (Application Programming Interface) for a full Lighthouse audit. Returns category scores (performance, accessibility, best practices, SEO (Search Engine Optimization)), detailed optimization opportunities with estimated savings, diagnostic information, and real-world loading experience data from CrUX. Supports both mobile and desktop strategies. Lighthouse 13 performance scoring weights: TBT 30%, LCP 25%, CLS 25%, FCP 10%, SI 10%.
If you're using an AI assistant through MCP, you don't need to understand any of the technical details — the assistant calls the tool and translates the result for you.
Why this specific tool matters
Let's skip the marketing fluff and answer the only question that actually matters: why should you, a real human with a real to-do list, care about the PageSpeed Insights tool? Here's the plain-English version, written the way you'd hear it from a friend who happens to do this for a living.
PageSpeed Insights is the industry standard for web performance measurement. Integrating it via API (Application Programming Interface) enables automated performance monitoring, automated deployment workflows gates, and competitive benchmarking without manual browser testing.
Picture this in real life. Imagine a performance engineer. Here's the situation they're walking into: Track PageSpeed scores over time to detect performance regressions after deployments. Without the right tool, that person would be stuck copy-pasting between five browser tabs, reading documentation written for engineers, and crossing their fingers that the answer they cobble together is correct. With the PageSpeed Insights tool, the same person gets a clear answer in seconds — no spreadsheets, no guessing, no waiting for someone on the infrastructure team to free up.
Three questions this tool answers in plain English. If any of these have ever crossed your mind, the PageSpeed Insights tool is built for you:
Are search engines actually able to crawl, understand, and recommend my pages?
What is the single biggest fix I could make today to climb in Google?
How does my site compare against the technical SEO checklist that the top results all pass?
You can either click the tool and get the answer yourself, or ask your AI assistant — connected through MCP (Model Context Protocol) — to ask the question for you and translate the answer into something you can paste into Slack.
Who gets the most out of this. Marketers, content writers, freelancers running client sites, founders trying to grow without paying for ads, and SEO specialists running monthly health checks. If you see yourself in that list, this is one of the EdgeDNS tools you should bookmark today.
What happens if you skip this entirely. Skip it and search engines quietly stop sending you traffic and you don't find out until the next quarterly review. That's why running this check — even once a month — is one of the cheapest forms of insurance you can give your domain.
Available on the developer plan. The technical details: `GET /v1/domain/pagespeed`.
When would I actually use this?
If you're still on the fence about whether the PageSpeed Insights tool belongs in your toolbox, this section is for you. Below you'll meet three real people — a performance engineer, a devops engineer, and a product manager — facing three real situations where this tool turns a stressful afternoon into a five-minute task. Read whichever story sounds closest to your week.
Story 1: Performance Monitoring
Imagine you're a performance engineer. Track PageSpeed scores over time to detect performance regressions after deployments.
Why it matters: Catch performance issues before they impact user experience and SEO (Search Engine Optimization).
Story 2: CI/CD Performance Gate
Imagine you're a devops engineer. Block deployments when PageSpeed performance score drops below a threshold.
Why it matters: Prevent performance regressions from reaching production.
Story 3: Competitive Benchmarking
Imagine you're a product manager. Compare PageSpeed scores against top competitors to identify performance gaps.
Why it matters: Set data-driven performance targets based on competitive landscape.
Common situations across teams. Beyond the three stories above, here are the everyday workplace moments when people across the company reach for the PageSpeed Insights tool — or one of the tools right next to it in this category. If any of these are on your calendar this month, that's your sign:
Before launching a new page, site, or campaign — to catch the dumb mistakes.
During a quarterly SEO health check.
When organic traffic suddenly drops and you need to find out why.
When pitching a new client and you need an audit deck in under an hour.
If you can see yourself in even one of those bullets, the PageSpeed Insights tool will pay for itself the first time you use it.
Still not sure? Here's the easiest test in the world. Open Claude, ChatGPT, Gemini, or any other AI assistant connected to the EdgeDNS MCP server and ask, in your own words: "Is the PageSpeed Insights tool useful for my job?" The assistant will look at the tool, ask you a couple of follow-up questions about what you're trying to accomplish, and give you a straight answer in plain English. No commitment, no signup forms, no jargon.
The easiest way: just ask your AI assistant
If you've connected the EdgeDNS MCP server to Claude, ChatGPT, Gemini, Cursor, or any other AI assistant, you don't need to write any code. Just ask in plain English:
"Use the PageSpeed Insights tool to check example.com and explain anything that looks wrong in plain language."
The AI will figure out which tool to call, fill in the right parameters, run it, and then explain the result back to you. No copy-pasting between tabs. No reading raw JSON. No memorizing endpoint names.
MCP (Model Context Protocol) access is free on every plan, including the free tier. One API key works for both REST and AI — you do not have to choose.
The technical way: call it from code
If you're a developer and want to call the endpoint from a script or your own application, here's the simplest possible example. Replace the placeholder API key with the real one from your dashboard.
# Replace edns_live_YOUR_KEY with your real API key from the dashboard
curl -H "Authorization: Bearer edns_live_YOUR_KEY" \
"https://api.edgedns.dev/v1/domain/pagespeed?domain=example.com"What you need to provide
You need to provide 2 pieces of information when you call this tool. The table below lays them out side by side, with a real example for each one so you can see exactly what to send.
| Field | Type | Required? | What it means | Example |
|---|---|---|---|---|
domain | string | Yes | The domain to run PageSpeed audit on | example.com |
strategy | string | Optional | Audit strategy: mobile or desktop (default: mobile) Allowed values: mobile, desktop | mobile |
What you get back
When you call this tool, you'll get back a JSON object with the fields below. If you're talking to it through an AI assistant, the assistant reads these for you and explains them in plain language — you don't need to memorize them.
| Field | Type | What you'll see in it |
|---|---|---|
domain | string | The audited domain |
strategy | string | The audit strategy used (mobile/desktop) |
fetchTime | string | ISO 8601 timestamp when the Lighthouse audit was performed |
scores | object | Category scores: performance, accessibility, bestPractices, SEO |
opportunities | array | Optimization opportunities with estimated savings |
diagnostics | array | Diagnostic information and display values |
redirects | array | Redirect chain with URLs and wasted time per redirect |
loadingExperience | object | Real-world CrUX loading experience metrics |
Words you might be wondering about
If any words on this page felt like jargon, here's a plain-language version. Click any linked term to read a full beginner-friendly guide.
API (Application Programming Interface) — A way for one program to ask another program for something — like a waiter taking your order to the kitchen.
SEO (Search Engine Optimization) — Everything you do to help search engines like Google find, understand, and rank your website.
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