These values appear in the developer tab of the scan report and provide deeper technical insight than the basic metrics.
DOM size
The number of all DOM elements on the page. From around 1,500 elements onwards, the browser becomes noticeably slower at rendering and at JavaScript operations.
Reference values:
| Elements | Assessment |
|---|---|
| Under 800 | Good |
| 800–1,500 | Okay |
| Over 1,500 | Elevated (Lighthouse reference value) – feeds into the score |
| Over 3,000 | Critical – noticeable score deduction |
A typical cause: page builders such as Elementor or Divi often produce a great many nested wrapper elements.
Blocking scripts
The number of external JavaScript files that are included without async or defer. These scripts block the browser while it parses the HTML, until they have been fully loaded and executed.
Reference values:
| Count | Assessment |
|---|---|
| 0 | Optimal |
| 1–3 | Acceptable |
| More than 3 | Should be reduced – feeds into the score |
| More than 8 | Critical – noticeable score deduction |
The affected script URLs are listed in the report.
font-display
Indicates whether a font-display value is set in the page's @font-face rules. If it is missing, the browser may keep text invisible until the font has fully loaded (FOIT – flash of invisible text).
turbometrics checks whether font-display is present in the analysed stylesheets:
- Present: the loading behaviour of the fonts is controlled
- Missing: FOIT risk – at least
font-display: swaporoptionalis recommended
Resource hints
Resource hints in the <head> allow the browser to bring DNS resolutions or connection set-ups forward, before resources are explicitly requested.
turbometrics detects:
<link rel="preconnect">: a prioritised early connection to important external hosts<link rel="dns-prefetch">: DNS pre-resolution for external hosts<link rel="prefetch">: preloading resources for the next navigation
If a page includes resources from many external hosts but has no resource hints set, turbometrics reports a notice.
Long tasks
Long tasks are tasks that block the browser main thread for longer than 50 ms. The blocking time is the portion beyond 50 ms – this time feeds directly into TBT.
turbometrics shows for each long task:
- the start time (measured from page load)
- the total duration
- the blocking time (colour-coded by severity)
- the likely cause (script URL, as far as it can be determined)
The likely cause is determined by overlap with the resource timings and is an approximation, not a proven fact.
Typical causes:
- heavy JavaScript bundles without code splitting
- third-party scripts (tracking, chat, consent banners)
- missing or late script prioritisation
- synchronously loaded plugins with their own JS logic
Resource breakdown
A breakdown of the resources loaded in the browser by type and weight:
| Type | Content |
|---|---|
| JS | JavaScript files |
| CSS | Stylesheets |
| IMG | Images |
| FONT | Font files |
| VIDEO | Video files |
The breakdown is based on browser runtime data. If JS data is not available (e.g. for cached resources), the static analysis value is used and marked accordingly.
Images without explicit dimensions
Images without width and height attributes can cause layout shifts while loading (CLS), because the browser cannot reserve space for them.
turbometrics shows the number of affected images as well as the total number of images detected on the page.
JavaScript and CSS files
Too many separate JS and CSS files add coordination overhead in the browser and often point to unfavourable asset management.
Reference values for JS files (included directly in the HTML):
| Count | Assessment |
|---|---|
| Up to 12 | Acceptable |
| 13–20 | Elevated – feeds into the score |
| More than 20 | Critical – noticeable score deduction |
Reference values for CSS files (included directly in the HTML):
| Count | Assessment |
|---|---|
| Up to 7 | Acceptable |
| 8–12 | Elevated – feeds into the score |
| More than 12 | Critical – noticeable score deduction |
A typical cause: every WordPress plugin often ships its own stylesheets and scripts, without these being bundled.
JavaScript weight
The total weight of all statically detected JavaScript files directly affects load time and browser runtime.
Reference values:
| Weight | Assessment |
|---|---|
| Under 350 KB | Good |
| 350–700 KB | Elevated – feeds into the score |
| Over 700 KB | Critical – noticeable score deduction |
Fonts
Too many or too heavy font files delay the rendering of visible text.
Reference values:
| Signal | Assessment |
|---|---|
| Up to 4 font files and under 250 KB in total | Good |
| More than 4 files or over 250 KB | Notable – feeds into the score |
Remedy: cut down the number of font variants (load only the weights and styles you actually use), use font subsetting and serve WOFF2 exclusively.
Requests and data volume
Besides individual resources, turbometrics also assesses the total number and total weight of all requests.
Reference values for requests:
| Count | Assessment |
|---|---|
| Up to 70 | Good |
| 71–120 | Elevated |
| More than 120 | Critical |
Reference values for total data volume:
| Weight | Assessment |
|---|---|
| Under 2 MB | Good |
| 2–4 MB | Elevated |
| Over 4 MB | Critical |
External hosts
Every external host requires its own DNS lookup and TLS handshake before resources can be loaded.
Reference value: more than 4 external hosts counts as notable.
Typical sources: tracking services, consent banners, fonts from Google Fonts, CDN integrations, chat widgets.
Uncached first-party assets
Your own static files without long-lived cache headers are transferred again on every page load.
Reference value: more than 10 uncached first-party assets counts as notable.
Images
The number and weight of images are assessed in context. WooCommerce shops and builder pages get higher tolerance values, because they naturally use more images.
Reference values for image count:
| Page type | Notable | Critical |
|---|---|---|
| Standard | > 10 | > 20 |
| Builder (Elementor, Divi, …) | > 15 | > 35 |
| WooCommerce | > 25 | > 60 |
Reference values for total image weight:
| Page type | Notable | Critical |
|---|---|---|
| Standard | > 1.2 MB | > 2.5 MB |
| Builder | > 1.6 MB | > 3.2 MB |
| WooCommerce | > 2.0 MB | > 4.5 MB |
Reference value for a single image:
| Page type | Notable |
|---|---|
| Standard | > 300 KB |
| Builder | > 350 KB |
| WooCommerce | > 400 KB |
Page build timing
The page build timeline shows the most important timing events while the page loads, in chronological order. It helps you spot the phase in which rendering stalls.
Waterfall
The resource waterfall shows all loaded resources with their start and end times. That makes loading orders, blockages and late third-party requests directly visible.
Further reading
→ Metrics → Problems & recommendations → Scoring & methodology