---
title: 'Identify Render-Blocking Assets and Slow Routes'
description: 'Learn how to find files that delay page rendering and routes that feel slow, using a beginner-friendly workflow in KaBOOM Agentic Devtools.'
canonical: https://gokaboom.dev/articles/identify-render-blocking-assets-and-slow-routes/
docs_version: 'v0.8.1'
docs_channel: 'latest'
last_verified_version: '0.8.0'
last_verified_date: 'Fri Mar 06 2026 00:00:00 GMT+0000 (Coordinated Universal Time)'
normalized_tags: ['performance', 'rendering', 'frontend', 'optimization', 'articles', 'identify', 'render', 'blocking', 'assets', 'slow', 'routes']
related_guides: ['/guides/debug-webapps/', '/guides/api-validation/', '/reference/observe/']
---

If a page shows a blank screen for too long, something is blocking rendering.

Rendering means “the browser drawing visible content.” This guide helps you locate blockers and fix them with *KaBOOM Agentic Devtools**.

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## Quick Terms

- **Render-blocking asset**: File that must load before content can appear.
- **Route**: A URL path in your app (for example `/checkout`).
- **Waterfall**: Ordered timeline of resource requests.

## The Problem You Are Solving

You want pages to feel fast at first glance, not just eventually complete.

## Step-by-Step with KaBOOM Agentic Devtools

### Step 1. Scan for performance bottlenecks

```js
analyze({what: "performance"})
```

### Step 2. Inspect waterfall timings

```js
observe({what: "network_waterfall", limit: 120})
```

Look for large scripts and stylesheets near the top of the waterfall.

### Step 3. Validate by route

```js
interact({what: "navigate", url: "https://app.example.com/checkout", include_content: true})
observe({what: "vitals"})
```

Repeat for key routes (`home`, `pricing`, `checkout`, `dashboard`).

### Step 4. Re-test after optimization

```js
analyze({what: "performance", summary: true})
```

## Typical Fixes

- Defer non-critical scripts.
- Split large bundles.
- Preload critical assets only.
- Move rarely used code behind lazy loading.

## Image and Diagram Callouts

> [Image Idea] Waterfall chart with render-blocking requests highlighted in red.

> [Diagram Idea] Route map with loading times per route (green/yellow/red).

## You’re Improving First Impressions

Fast first paint builds trust. *KaBOOM Agentic Devtools** gives you a practical way to prioritize what truly affects user experience.