Mcmaster: a phone-and-desktop teardown
We loaded https://mcmaster.com 4 times on a simulated iPhone and 2 more on a 1366px desktop, and wrote down what a real visitor would see on each. No login, no insider access, no Harvv pixel needed. Here is what repeated visits already show, sorted by how we know it.
TL;DRWhat jumped out
Of everything we found on this scan, this is the one to start with: Images without sizes set make the page jump as it loads. 30 of 30 images on this page don't have width and height set. As each image finishes loading, the content below it slides down to make room. The visitor goes to tap one thing and ends up tapping another, and the cause is invisible to them.
Below: what's already working, every finding ranked by impact and tagged with the screen it affects, the speed numbers on phone and desktop, and a checklist of what to fix first.
00What's already working
Start here so the problems below are in context. These held up across the test loads:
- Speed is good. The main content paints in about 0.3s in our test loads, inside Google's 2.5s "good" threshold. Real networks are slower, but the page itself is not heavy.
- Light page weight. The page is about 0.7 MB across 60 requests. That keeps it quick on mobile data and cheap to load repeatedly.
- Search basics are in place. Lighthouse scores SEO 92/100. The fundamentals Google looks for are present.
- Layout holds on phone and desktop. Nothing spilled past the edge at either 390px (phone) or 1366px (desktop), so the structure is responsive.
This is one of several industrial supply sites we tore down the same way. The same friction repeats on Fastenal, and we pulled the cross-site pattern together in the industrial web report.
01Findings, ranked by what hurts conversion most
| Severity | Finding | How we know |
|---|---|---|
| High | Images without sizes set make the page jump as it loadsBothPerformanceSEO 30 of 30 images on this page don't have width and height set. As each image finishes loading, the content below it slides down to make room. The visitor goes to tap one thing and ends up tapping another, and the cause is invisible to them. The exact images we found: paste into Claude, Cursor, or ChatGPT | |
| High | JavaScript errors were logged during loadBothConversionTracking Errors in the console often mean a feature silently broke: a button that does nothing, analytics that did not fire, a form that will not submit. paste into Claude, Cursor, or ChatGPT | |
| High | Some buttons have no accessible nameBothAccessibility (WCAG)Tracking A button with only an icon and no label is announced as "button" by screen readers, giving no idea what it does. paste into Claude, Cursor, or ChatGPT | |
| Medium | Google is writing your search snippet for youBothSEO This page has no meta description, so Google grabs whatever text it finds on the page and shows that under your title in search results. Usually it's not the pitch you'd write yourself. Adding a 120 to 160 character summary is one of the easier wins for search click-through. paste into Claude, Cursor, or ChatGPT | |
| Medium | 1 form field has no labelBothAccessibility (WCAG)ConversionTracking Screen readers can't announce these fields, and a sighted user who clears the placeholder can't recover the prompt. Wrap each input in <label>…</label> or add aria-label. The exact elements we found: paste into Claude, Cursor, or ChatGPT | |
| Medium | No analytics installed, so you cannot see your own trafficBothTracking No Google Analytics, GA4, or any analytics tag was detected. There is no way to know how many visitors arrive, where they come from, or what converts, and no data to retarget or measure a campaign against. Installing GA4 (free) is the baseline. paste into Claude, Cursor, or ChatGPT | |
| Medium | Duplicate title tagsBothSEO The same <title> appears on multiple pages. Duplicate titles confuse search engines about which page to rank and split relevance between them. (Found across a sample of 8 pages from your sitemap, a partial crawl rather than your full site.) The exact examples we found:
paste into Claude, Cursor, or ChatGPT | |
| Low | Search-result title is leaving room on the tableBothSEO Google gives you about 60 characters of headline space in search results. This page is using 13. Adding the value proposition or a relevant keyword gives someone one more reason to click. paste into Claude, Cursor, or ChatGPT | |
| Low | No canonical tag, so duplicate URLs split the page's rankingBoth When the same content is reachable at multiple URLs (think tracking parameters or session IDs), Google can split your ranking signal across them. A single canonical tag tells Google which version counts. paste into Claude, Cursor, or ChatGPT | |
| Low | Links to this page will look bare when sharedBoth The page is missing its Open Graph title and image, so when someone shares it on Facebook, LinkedIn, iMessage, or Slack the preview has no title and image. A flat grey link gets far fewer clicks than one with an image and headline. paste into Claude, Cursor, or ChatGPT | |
| Low | No structured data for rich search resultsBoth The page has no schema.org markup. Adding the right type (Product, Article, Organization, FAQ) lets Google show rich results like star ratings and prices, which lift click-through for free. paste into Claude, Cursor, or ChatGPT | |
| Low | No email capture or newsletter detectedBothConversion No email-marketing tag (Klaviyo, Mailchimp, etc.) was found. Email capture plus a welcome and abandoned-cart flow is consistently the highest-ROI addition for a small store, and it is owned audience you keep regardless of ad costs. paste into Claude, Cursor, or ChatGPT | |
| Low | No visible contact details (email or phone)BothConversion The page exposes no email or phone link. For higher-value or trust-sensitive purchases, a clear way to reach a human reduces hesitation. Add an email or phone link in the header or footer. paste into Claude, Cursor, or ChatGPT | |
| Low | Unused JavaScript is being downloadedBothPerformance Code that never runs on this page still costs download and parse time on every visit. Splitting or removing it speeds up load. Lighthouse measured: Est savings of 216 KiB. paste into Claude, Cursor, or ChatGPT | |
| Low | Unused CSS is being downloadedBothPerformance Style rules that this page never uses still block rendering while they download. Trimming them frees the paint path. Lighthouse measured: Est savings of 35 KiB. paste into Claude, Cursor, or ChatGPT | |
| Low | Sitemap URL redirectsBothSEO A URL listed in your sitemap redirects to a different URL. Sitemaps should list final destination URLs; redirected entries waste crawl budget and dilute ranking signals. (Found across a sample of 8 pages from your sitemap, a partial crawl rather than your full site.) The exact examples we found:
paste into Claude, Cursor, or ChatGPT | |
| Low | No Organization or WebSite schemaBothSEO No site-wide Organization or WebSite structured data found on any crawled page. This is the schema that tells Google and AI engines who you are (name, logo, social profiles) for the knowledge panel and brand recognition in AI answers. (Found across a sample of 8 pages from your sitemap, a partial crawl rather than your full site.) paste into Claude, Cursor, or ChatGPT |
Accessibility findings are automated checks against Web Content Accessibility Guidelines (WCAG) 2.1 and 2.2. They flag potential barriers and legal risk, not a certification or a determination of compliance with the ADA, Section 508, or EN 301 549. Automated testing catches only a subset of issues; a full conformance review needs manual and assistive-technology testing by a qualified reviewer.
"How we know": unlabeled = a deterministic fact, identical on every load (e.g. element sizes). Most findings are this kind, so we only mark the exceptions: median across loads = a noisy lab metric, reported as a median. real-user field data = Google CrUX, actual Chrome visitors.
Structural and AI-search checks crawl up to 8 pages from your sitemap (a sample, not your full site). "Broken" means a link returned 404, 410, or 5xx, or did not respond; access-controlled pages (401, 403) are not counted.
02Performance: phone, desktop, and real visitors
| Metric | Mobile | Desktop | Read |
|---|---|---|---|
| TTFB (lab median) | 175 ms | 114 ms | Lab |
| FCP (lab median) | 300 ms | 202 ms | Lab |
| LCP (lab median) | 326 ms | 202 ms | Good |
| Page weight (median) | 0.7 MB | 1.5 MB | OK |
Google Lighthouse (lab): Performance 78 mobile / 94 desktop, SEO 92, Accessibility 92, Best Practices 96.
Lab numbers are from a headless mobile browser on an unthrottled connection: treat them as a floor, not a typical experience. Add a Google API key to light up real-user field data (CrUX) and Lighthouse scores.
03Tiny buttons are hard to tap on mobile
6 of 32 tappable items on this page come in below 44×44 pixels, the size Apple and Google both recommend for reliable tapping on a phone. The same ones came up small on every one of the 4 test loads, so this is the page itself, not a fluke.
The buttons measuring below the minimum on this scan:
- a 390x30 "McMaster-Carr logo"
- button 16x16 (no visible label)
- button 24x24 (no visible label)
- a 64x35 "ORDER"
- button 40x40 "open menu"
- a 246x12 "Terms and Conditions and Pri"
The fix is CSS-only on most sites: add padding around the icon (don't just change the icon size) so the actual tap area is at least 44×44 pixels. No redesign, no new assets.
04Technical SEO & structured data
| Check | Result |
|---|---|
| Title | McMaster-Carr (13 chars) |
| Meta description | Missing |
| H1 | 1 on page |
| Canonical | Missing |
| Structured data (JSON-LD) | None |
| Open Graph | Incomplete |
05The fix checklist
Everything to fix, priority first, each tagged with the screen it affects and a rough effort. Work top to bottom.
- Images without sizes set make the page jump as it loadsBothCSS only
- JavaScript errors were logged during loadBothDev afternoon
- Some buttons have no accessible nameBothVaries
- Google is writing your search snippet for youBoth1 line
- 1 form field has no labelBothVaries
- No analytics installed, so you cannot see your own trafficBothDev afternoon
- Duplicate title tagsBoth1 line
- Search-result title is leaving room on the tableBoth1 line
- No canonical tag, so duplicate URLs split the page's rankingBoth1 line
- Links to this page will look bare when sharedBoth1 line
- No structured data for rich search resultsBothVaries
- No email capture or newsletter detectedBothVaries
- No visible contact details (email or phone)BothVaries
- Unused JavaScript is being downloadedBothVaries
- Unused CSS is being downloadedBothVaries
- Sitemap URL redirectsBothVaries
- No Organization or WebSite schemaBothVaries
Effort is a rough read from the outside: "CSS only" means no new assets or backend work, "1 line" means a single tag, "Dev afternoon" means a developer needs to touch tracking or scripts.
06What this report cannot tell you
Everything above is from the outside, looking at the page on a simulated phone and desktop. The questions that actually decide revenue need real visitors. Install the Harvv pixel (one script tag, 16 KB, zero personal data, no engineering project) and within about 72 hours you'd know which buttons real customers tapped and missed, how often Google Analytics is missing visits, and exactly where mobile shoppers stalled and left. This report shows you where to look. The pixel shows you how often it happens, and to whom.
Drop the Harvv pixel on mcmaster.com and we turn this one-off scan into ongoing measured behavior: which taps miss, where sessions stall, and the real drop rates. Free to start, no card needed.
Add the pixel free07How we did this, and what it can't prove
- 4 mobile + 2 desktop loads of one URL from headless Chrome (iPhone viewport at 390px, desktop at 1366px), June 29, 2026. Enough loads to separate real defects from random noise, not a full-site crawl.
- Lab numbers, not real-user numbers (no field data was available for this run). Real devices on real networks run slower.
- Friction is inferred, not counted. We can prove a button is small. We can't, from the outside, count how often it causes a missed tap. That requires the pixel on a live page.
Prepared by Harvv. Last updated June 29, 2026.