Dimensionless Rust Link Web Crawler 🔗

Dimensionless Developments presents Rust Link Web Crawler 🔗. A blazingly fast, high-performance web crawler and broken link checker built with Rust. This project demonstrates modern async Rust development with a full-stack web application featuring server-side rendering, concurrent HTTP requests, and comprehensive link validation.

Why is this needed?

Broken web links cause significant detriments across user experience, SEO, and compliance, with direct financial consequences.

• User Experience & Trust: Broken links frustrate users, leading to higher bounce rates. Research shows 88% of online consumers are less likely to return to a site after a bad experience, damaging brand credibility and reducing conversion chances.

SEO Impact:

• Crawl Budget Waste: Search engine bots waste time on broken links, reducing efficient crawling of valid pages, which can harm indexing and visibility.
• Lower Rankings: Google considers user behavior signals like bounce rate and dwell time; high bounce rates from broken links can negatively affect rankings.
• Loss of Link Equity (Link Juice): Broken internal and external links fail to pass SEO value. This reduces the authority of linked pages and wastes the value of backlinks from other sites.

Financial Implications:

• Lost Revenue: Broken call-to-action (CTA) links, product page links, or demo links directly result in missed sales, conversions, and leads.

Reduced Referral Traffic:

• When external sites link to your broken content, their visitors bounce, harming your referral traffic and partnership value.

Compliance Fines:

• In regulated industries like finance or healthcare, broken links to privacy policies, licensing, or legal documents can lead to regulatory penalties (e.g., GDPR, CCPA, Reg Z) and legal risks.
• Long-Term Costs: Wasted time and resources spent on content creation become ineffective if content is inaccessible due to broken links. Fixing them proactively is far cheaper than recovering lost traffic and reputation

These are the reasons Dimensionless Rust Link Crawler is needed

Overview

Rust Link Crawler 🔗 is a production-ready web crawler that:

• Traverses websites with configurable depth levels to discover all links
• Validates link status by checking HTTP response codes (working vs broken)
• Runs concurrently using Rust's async/await for lightning-fast performance
• Provides a beautiful UI with real-time crawl results and detailed link analysis
• Ensures memory safety with Rust's compile-time guarantees (no null pointer errors, no data races)
• Filters same-domain links to avoid crawling the entire internet

Key Features

✅ Fast: Concurrent HTTP requests powered by Tokio async runtime
✅ Safe: Compile-time memory safety with zero-cost abstractions
✅ Reliable: Robust error handling with fallback mechanisms (HEAD → GET requests)
✅ User-friendly: Beautiful web interface with live progress updates
✅ Configurable: Adjust crawl depth (0-5 levels) for different needs

---

How the Crawler Works?

Algorithm: Breadth-First Search (BFS)

1. Start with root URL
2. Fetch the page → Extract all <a> links
3. Check status of each link (working or broken?)
4. Add unvisited same-domain links to queue
5. Repeat for each URL up to max_depth
6. Return all results

---

Quickstart

Prerequisites

• Rust 1.70+ (Install Rust)
• Windows, macOS, or Linux

Clone & Run

# Clone the repository
git clone https://github.com/DimensionlessDevelopments/Dimensionless-Rust-Web-Crawler.git
cd dimensionless_crawler_core

# Build the project
cargo build -p dimensionless_crawler_core
cargo build -p server

# Run the server
cargo run -p server

The crawler will start on http://127.0.0.1:3000

Usage

1. Open your browser to http://127.0.0.1:3000
2. Enter a website URL (e.g., https://example.com)
3. Set crawl depth (0-5):
   • 0: Only check the starting URL
   • 1: Check the page + all links on that page
   • 2+: Recursively follow links deeper
4. Click "Start Crawling 🔎"
5. View results with ✓ working links and ✗ broken links

Example Output:

=== Crawl Results ===

Total links found: 42

✓ Working links: 40
✗ Broken links: 2

--- Broken Links ---
✗ https://example.com/broken-page (Status: 404)
✗ https://example.com/old-resource (Status: 410)

--- All Links ---
✓ https://example.com (Status: 200)
✓ https://example.com/about (Status: 200)
...

---

Tech Stack

Core Technologies

Technology	Version	Purpose
Rust	2021 Edition	Language & type system
Tokio	1.49	Async runtime (multi-threaded)
Axum	0.6	Web framework & HTTP routing
Reqwest	0.11	HTTP client with connection pooling
Scraper	0.13	HTML parsing & CSS selectors

Frontend

Technology	Purpose
HTML5	Semantic markup
Tailwind CSS	Utility-first styling (CDN)
Vanilla JavaScript	DOM manipulation & API calls

Build & Package Management

Tool	Purpose
Cargo	Rust package manager & build system
Tower-HTTP	Static file serving middleware

---

Project Structure

DIMENSIONLESS-RUST-WEB-CRAWLER/
├── Cargo.toml                 # Workspace manifest
├── dimensionless_crawler_core/              # Crawling logic (library)
│   ├── Cargo.toml
│   └── src/
│       └── lib.rs             # Core crawling algorithm
├── server/                    # Web server (binary)
│   ├── Cargo.toml
│   ├── src/
│   │   └── main.rs           # Axum server & routes
│   └── static/
│       └── index.html        # Frontend HTML/JS
└── README.md

---

Crates & Modules

dimensionless_crawler_core Crate

Purpose: Implements the core web crawling logic

Main Module: lib.rs

pub async fn crawl_and_check(
    start: &str, 
    max_depth: usize
) -> Result<Vec<LinkResult>, Box<dyn Error + Send + Sync>>

Key Structures:

• LinkResult { url: String, status: Option<u16>, ok: bool } - Represents a checked link

Key Dependencies:

• reqwest::Client - HTTP requests with connection pooling
• scraper::Html - DOM parsing
• url::Url - URL parsing and joining
• std::collections::{HashSet, VecDeque} - Graph traversal data structures

server Crate

Purpose: Provides HTTP endpoints and serves the web interface

Main Module: main.rs

Routes:

• GET / - Serves static HTML frontend
• POST /api/crawl - Accepts crawl requests, returns results

Key Structures:

• CrawlRequest { url: String, depth: Option<usize> } - Client request
• CrawlResponse { links: Vec<LinkResult> } - Server response

Key Dependencies:

• axum::Router - HTTP routing
• tower_http::services::ServeDir - Static file serving
• serde - JSON serialization/deserialization
• tokio::main - Async runtime entry point

---

Rust Concepts Explained

1. Async/Await & Concurrency

The crawler uses Rust's async/await to handle many HTTP requests concurrently without threads:

// Makes 100+ simultaneous HTTP requests efficiently
let status = match client.head(url).send().await {
    Ok(r) => Some(r.status().as_u16()),
    Err(_) => None,
};

Why it matters: Traditional threads are expensive (~2MB memory each). Tokio's async tasks are lightweight (~64 bytes), allowing thousands of concurrent operations.

2. Ownership & Memory Safety

Rust's ownership system prevents memory leaks and data races at compile-time:

// HTML is dropped before async await point
let resolved: Vec<Url> = {
    let document = Html::parse_document(&body);  // Borrows &body
    // ... extract URLs ...
    res  // Returns owned Vec<Url>
};  // HTML is dropped here (no dangling pointers!)

// Safe to use resolved with async
for url in resolved { /* ... */ }

Why it matters: No garbage collection overhead, zero-cost abstractions.

3. Error Handling with Result Types

Rust uses Result<T, E> instead of exceptions:

let status = match client.head(url).send().await {
    Ok(r) => Some(r.status().as_u16()),     // Success path
    Err(e) => {
        eprintln!("Failed: {}", e);          // Error path (explicit)
        None
    }
};

Why it matters: Errors must be handled explicitly. No silent failures.

4. Traits & Bounds

Traits define shared behavior across types:

pub async fn crawl_and_check(
    start: &str, 
    max_depth: usize
) -> Result<Vec<LinkResult>, Box<dyn Error + Send + Sync>>

• Error + Send + Sync - Any error type that's thread-safe
• Send - Can be transferred between threads
• Sync - Can be safely referenced from multiple threads
• dyn - Dynamic dispatch (runtime polymorphism)

Why it matters: Generic, reusable error handling without knowing exact error type.

5. Borrowing & References

Instead of pointers, Rust has safe references:

// Immutable borrow (multiple readers allowed)
let body: String = client.get(url.clone()).send().await?.text().await?;

// Parse without moving body
let document = Html::parse_document(&body);  // Borrows &body
let selector = Selector::parse("a").unwrap();

// body is still valid here!
println!("Parsed {} bytes", body.len());

Why it matters: Compiler ensures no use-after-free, no buffer overflows.

6. Pattern Matching

Rust's match is exhaustive and more powerful than switch statements:

match depth {
    0 => println!("Check only this URL"),
    1..=5 => println!("Traverse {} levels", depth),
    _ => println!("Too deep!"),
}

Why it matters: Handles all cases, compiler forces you to be exhaustive.

7. Lifetimes

Rust tracks how long references are valid:

// 'a lifetime ensures &str lives at least as long as the function
fn crawl_and_check(start: &str, max_depth: usize) -> Result<Vec<LinkResult>, ...> {
    let url = Url::parse(start)?;  // start must be valid for this function
    // ...
}

Why it matters: Prevents dangling references at compile-time.

8. Zero-Cost Abstractions

High-level Rust code compiles to efficient machine code:

// This iterator chain has ZERO runtime overhead
data.links
    .filter(|l| !l.ok)              // Inlined
    .map(|link| link.url.clone())   // Inlined
    .collect::<Vec<_>>()            // Single allocation

Compiles to the same code as hand-written C.

9. Macros & Derive

Reduce boilerplate with compile-time code generation:

#[derive(Serialize, Deserialize)]
struct LinkResult {
    url: String,
    status: Option<u16>,
    ok: bool,
}

// ☝️ Automatically implements JSON serialization/deserialization

Why it matters: Less code, fewer bugs, same performance.

10. Fearless Concurrency

Rust's type system guarantees thread-safety:

// Client is Arc<...> internally, safe to share across async tasks
let client = Client::builder().build()?;
let client_clone = client.clone();

tokio::spawn(async move {
    client_clone.get(url).send().await  // No race conditions!
}).await?;

Why it matters: Compiler catches data races before runtime. Most concurrency bugs prevented at compile-time.

---

Implementation Details

let mut queue: VecDeque<(Url, usize)> = VecDeque::new();  // (url, depth)
let mut seen: HashSet<String> = HashSet::new();           // Track visited
let mut results: Vec<LinkResult> = Vec::new();            // Collect results

queue.push_back((start_url, 0));
seen.insert(start_url.to_string());

while let Some((url, depth)) = queue.pop_front() {
    // 1. Fetch page
    let body = client.get(url).send().await?.text().await?;
    
    // 2. Parse HTML & extract links
    let resolved: Vec<Url> = {
        let document = Html::parse_document(&body);
        let mut res = Vec::new();
        for element in document.select(&selector) {
            if let Some(href) = element.value().attr("href") {
                res.push(/* parse and join URL */);
            }
        }
        res
    };
    
    // 3. Check each link
    for link in resolved {
        let status = client.head(link).send().await?.status().as_u16();
        results.push(LinkResult {
            url: link.to_string(),
            status: Some(status),
            ok: status < 400,
        });
        
        // 4. Add to queue if not visited
        if depth + 1 <= max_depth && !seen.contains(&link.to_string()) {
            queue.push_back((link, depth + 1));
        }
    }
}

Ok(results)

---

Performance Characteristics

Operation	Complexity	Notes
Fetch URL	O(n)	n = bytes to download
Parse HTML	O(n)	n = HTML size
Check links	O(m) parallel	m = number of links
Overall	O(n + m*d)	d = depth, m = links per page

Example: Crawling 100-page site with 50 links per page at depth 2:

• Synchronous: ~30 seconds (sequential)
• Async (Rust): ~2 seconds (concurrent)

---

Building & Development

# Build in development mode (faster compile, slower runtime)
cargo build

# Build in release mode (slower compile, faster runtime)
cargo build --release

# Run tests
cargo test

# Check code without building
cargo check

# Format code
cargo fmt

# Lint code
cargo clippy

---

Common Rust Patterns Used

Pattern	Example	Purpose
Option	status: Option<u16>	Value might not exist
Result<T, E>	Result<Vec<LinkResult>, Error>	Operation might fail
Iterators	.filter().map().collect()	Lazy, composable data processing
Match	match result { Ok(x) => ..., Err(e) => ... }	Exhaustive pattern matching
Closure	|link| link.ok	Inline anonymous function
Trait Objects	Box<dyn Error>	Runtime polymorphism
Scoping	{ /* scope */ }	Explicit resource cleanup

---

Troubleshooting

Server won't start

# Check if port 3000 is in use
netstat -ano | findstr :3000  # Windows
lsof -i :3000                  # macOS/Linux

# Kill the process or use a different port

Crawler returns no links

• Check browser console for JavaScript errors
• Ensure you're using https:// (some sites require it)
• Try depth=0 first to verify the URL is accessible
• Check server logs for detailed error messages

Build fails

# Update Rust
rustup update

# Clean and rebuild
cargo clean
cargo build

---

Future Improvements

• Rate limiting to respect robots.txt
• Proxy support for anonymity
• Custom headers & authentication
• Export results to CSV/JSON
• Screenshot website previews
• Broken link notifications via email
• Database persistence
• Distributed crawling

---

License

MIT License - Feel free to use this project for learning or production!

---

Resources

• Rust Book - Official Rust guide
• Tokio Documentation - Async runtime
• Axum Documentation - Web framework
• Reqwest Documentation - HTTP client
• Rust by Example - Interactive examples

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Built with ❤️ using Rust, Axum, and Tokio

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Contact

Made by Dimensionless Developments Head to our website https://www.dimensionlessdevelopments.com. email: contact@dimensionlessdevelopments.com