[Crawl-Date: 2026-04-26]
[Source: DataJelly Visibility Layer]
[URL: https://datajelly.com/seo-tools/page-speed-analyzer]
---
title: Real-Time Page Load Test — Mobile vs Desktop | DataJelly
description: Test how fast your page loads for mobile and desktop bots simultaneously. Real-time TTFB, JS render time, resource analysis, and side-by-side comparison.
url: https://datajelly.com/seo-tools/page-speed-analyzer
canonical: https://datajelly.com/seo-tools/page-speed-analyzer
og_title: DataJelly - The Visibility Layer for Modern Apps
og_description: Rich social previews for Slack & Twitter. AI-readable content for ChatGPT & Perplexity. Zero-code setup.
og_image: https://datajelly.com/datajelly-og-image.png
twitter_card: summary_large_image
twitter_image: https://datajelly.com/datajelly-og-image.png
---

# Real-Time Page Load Test — Mobile vs Desktop | DataJelly
> Test how fast your page loads for mobile and desktop bots simultaneously. Real-time TTFB, JS render time, resource analysis, and side-by-side comparison.

---

Performance Tool
## Real-Time Page Load Test

Mobile vs Desktop — raw fetch + full JS render, compared side by side

We test your page two ways: a raw HTTP fetch (what basic crawlers see) and a full browser render (executing all JavaScript). This reveals the true load time for JS-heavy sites like SPAs and React apps.

**Live HTTP test** — We fetch your page right now and measure real response times, content delivery, and JS rendering as it happens.

**How is this different from Lighthouse?**

- **Lighthouse** — simulated environment, throttled CPU/network, lab-based scores (Performance, Accessibility, SEO)
- **This tool** — real HTTP requests to your server, actual TTFB, real JS execution time, real content delivery

Lighthouse scores are useful benchmarks. This shows what bots and users actually experience *right now*.

## Enter URL to Test

We'll run raw HTTP fetch + full JS render for both mobile and desktop simultaneously

Test Page

Test as:
Human BrowserGooglebotGoogle vs Human

## What This Test Does

This tool runs **two layers of testing** on your URL: a raw HTTP fetch (what basic crawlers see) and a **full browser render** (executing all JavaScript). Both are run for mobile and desktop simultaneously.

The raw fetch measures TTFB and HTML transfer speed. The browser render measures the **true load time** — how long it takes for JavaScript to execute and build the actual page content. For JS-heavy SPAs, these numbers can differ dramatically.

Use the **Google vs Human** mode to see if your server returns different content to search engine crawlers — this is how you verify that prerendering or edge rendering is working correctly.

## Why JS Render Time Matters

A fast TTFB means nothing if your page takes 5 seconds to render content via JavaScript. Google's crawlers **do execute JavaScript**, but with a delay — pages go through a two-phase indexing process. Heavy JS overhead means your content takes longer to be discovered and indexed.

The **Content Gap** metric shows how many words of content JavaScript adds. If most of your content is JS-generated, basic crawlers (and many AI bots) will see a nearly empty page.

## What the Metrics Mean
## TTFB (Time to First Byte)

How long the server takes to respond. Under 200ms is fast, over 800ms is slow. Affected by server processing, database queries, and network distance.
## Full Render Time

Total time for a real browser to load and execute all JavaScript. This is the true user experience. Compare with TTFB to see how much JS adds.
## JS Overhead

The difference between Full Render Time and TTFB. Shows how much time JavaScript execution adds. High overhead suggests the site needs SSR or code splitting.
## Content Gap

Words added by JavaScript. If raw HTML has 50 words but rendered has 500, that's a 450-word gap — meaning most content is invisible to non-JS crawlers.
## Render-Blocking Resources

Scripts and stylesheets that must load before the page can render. Each one adds latency. Use async, defer, or inline critical resources.
## DOM Elements

A count of HTML elements. Raw vs rendered shows how much the DOM grows from JavaScript. Large DOMs slow parsing and rendering.

## Discovery & Navigation
> Semantic links for AI agent traversal.

* [DataJelly Edge](https://datajelly.com/products/edge)
* [DataJelly Guard](https://datajelly.com/products/guard)
* [Pricing](https://datajelly.com/pricing)
* [SEO Tools](https://datajelly.com/seo-tools)
* [Visibility Test](https://datajelly.com/visibility-test)
* [Dashboard](https://dashboard.datajelly.com/)
* [Blog](https://datajelly.com/blog)
* [Guides](https://datajelly.com/guides)
* [Getting Started](https://datajelly.com/guides/getting-started)
* [Prerendering](https://datajelly.com/prerendering)
* [SPA SEO Guide](https://datajelly.com/guides/spa-seo)
* [About Us](https://datajelly.com/about)
* [Contact](https://datajelly.com/contact)
* [Terms of Service](https://datajelly.com/terms)
* [Privacy Policy](https://datajelly.com/privacy)