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Is PageSpeed Insights enough, or do you need a paid speed testing tool?
Summary
For finding out why a page is slow, PageSpeed Insights and Lighthouse are free and usually enough. Paid tools earn their fee when you want the same pages tested on a schedule and an alert when they get slower. GTmetrix starts at $4.99 a month on yearly billing and WebPageTest Pro at $180 a year, and in both cases you are paying for monitoring slots and longer result history, not a better measurement.
Two kinds of data on one screen
The top half of a PageSpeed Insights report comes from the Chrome User Experience Report, which collects what real Chrome users experienced over the previous 28 days. The bottom half is a Lighthouse run in a simulated environment, scored for performance, accessibility, best practices and SEO.
Only the top half decides whether a page passes Core Web Vitals. It passes when the 75th percentile of LCP, INP and CLS are all in the good range: 2.5 seconds or less for LCP, 200 milliseconds or less for INP, and 0.1 or less for CLS. Google says plainly that a green lab score of 90 or more does not mean real users are having a good experience.
New or low-traffic pages often have too little field data. PSI then falls back to data for the whole origin, and if the origin is also too small, the field section stays empty. No paid tool can fill that gap, because the numbers come from Chrome users, not from the tool.
Why the score moves when nothing changed
Run Lighthouse twice and you may get two scores. Chrome's documentation puts most of that down to the conditions around the test: ads or A/B tests on the page, internet routing, the device, browser extensions and antivirus software. It suggests thinking of performance as a spread of scores. It also calls a perfect 100 extremely hard to reach and not expected.
Lighthouse runs from Chrome DevTools, from the command line and as a Node module, besides powering PSI. DevTools can test pages behind a login.
What the paid plans add
GTmetrix sells monitoring by the slot. One slot is one URL paired with one set of test conditions, such as location, device and connection speed, so watching a home page on both mobile and desktop takes two. The yearly-billed plans:
- Lite, $4.99 a month: 50 on-demand tests a month, one slot, no hourly monitoring, one month of data retention.
- Core, $9.99 a month: 150 tests, three slots, no hourly monitoring, six months of retention.
- Advanced, $24.99 a month: unlimited on-demand tests under a fair-use policy, ten slots, hourly monitoring, six months of retention.
- Expert, $49.99 a month: 50 slots, five team seats, 12 months of retention.
A free GTmetrix account can still monitor one URL daily, weekly or monthly. Hourly checks on ten key pages need Advanced, which comes to $299.88 a year.
WebPageTest's free Starter plan gives 150 test runs a month and keeps results for 60 days. Pro starts at $180 a year, with run allowances from 1,000 to 20,000 a month. It adds scheduled tests, alerts, API access and private tests, keeps results for 13 months, and allows up to five team members.
Work out your own number: the SEO Tools Cost Calculator finds the cheapest published plan for your sites, tracked keywords and users.
Sources
- https://developers.google.com/speed/docs/insights/v5/about
- https://developer.chrome.com/docs/lighthouse/overview
- https://developer.chrome.com/docs/lighthouse/performance/performance-scoring
- https://gtmetrix.com/pricing/
- https://gtmetrix.com/faq.html
- https://www.logicmonitor.com/pricing/web-performance-optimization
Figures come from each vendor's own pricing pages and documentation. We have not tested these tools hands-on, and no ranking here is paid for.