// Bad: URL gets cluttered with defaults
?theme=light&lang=en&page=1&sort=date

// Good: Only non-default values in URL
?theme=dark  // light is default, so omit it

function getTheme(params) {
return params.get('theme') || 'light'; // Default handled in code
}

import { debounce }...

{/* Your filtered products render here */} </div> ); }

Best Practices for URL State Management

Now that we’ve seen how URLs can hold application state, let’s look at a few best practices that keep them clean, predictable, and user-friendly.

Handling Defaults Gracefully

Don’t pollute URLs with default values:

// Bad: URL gets cluttered with defaults
?theme=light&lang=en&page=1&sort=date

// Good: Only non-default values in URL
?theme=dark  // light is default, so omit it

Use defaults in your code when reading parameters:

function getTheme(params) {
return params.get('theme') || 'light'; // Default handled in code
}

Debouncing URL Updates

For high-frequency updates (like search-as-you-type), debounce URL changes:

import { debounce } from 'lodash';

const updateSearchParam = debounce((value) => {
const params = new URLSearchParams(window.location.search);
if (value) {
params.set('q', value);
} else {
params.delete('q');
}
window.history.replaceState({}, '', `?${params.toString()}`);
}, 300);

// Use replaceState instead of pushState to avoid flooding history

pushState vs. replaceState

When deciding between pushState and replaceState, think about how you want the browser history to behave. pushState creates a new history entry, which makes sense for distinct navigation actions like changing filters, pagination, or navigating to a new view — users can then use the Back button to return to the previous state. On the other hand, replaceState updates the current entry without adding a new one, making it ideal for refinements such as search-as-you-type or minor UI adjustments where you don’t want to flood the history with every keystroke.

URLs as Contracts

When designed thoughtfully, URLs become more than just state containers. They become contracts between your application and its consumers. A good URL defines expectations for humans, developers, and machines alike

Clear Boundaries

A well-structured URL draws the line between what’s public and what’s private, client and server, shareable and session-specific. It clarifies where state lives and how it should behave. Developers know what’s safe to persist, users know what they can bookmark, and machines know whats worth indexing.

URLs, in that sense, act as interfaces: visible, predictable, and stable.

Communicating Meaning

Readable URLs explain themselves. Consider the difference between the two URLs below.

https://example.com/p?id=x7f2k&v=3
https://example.com/products/laptop?color=silver&sort=price

The first one hides intent. The second tells a story. A human can read it and understand what they’re looking at. A machine can parse it and extract meaningful structure.

Jim Nielsen calls these “examples of great URLs”. URLs that explain themselves.

Caching and Performance

URLs are cache keys. Well-designed URLs enable better caching strategies:

• Same URL = same resource = cache hit
• Query params define cache variations
• CDNs can cache intelligently based on URL patterns

You can even visualize a user’s journey without any extra tracking code:

graph LR
A["/products"] --> |selects category| B["/products?category=laptops"]
B --> |adds price filter| C["/products?category=laptops&price=500-1000"]

style A fill:#e9edf7,stroke:#455d8d,stroke-width:2px;
style B fill:#e9edf7,stroke:#455d8d,stroke-width:2px;
style C fill:#e9edf7,stroke:#455d8d,stroke-width:2px;

Your analytics tools can track this flow without additional instrumentation. Every URL parameter becomes a dimension you can analyze.

Versioning and Evolution

URLs can communicate API versions, feature flags, and experiments:

?v=2                   // API version
?beta=true             // Beta features
?experiment=new-ui     // A/B test variant

This makes gradual rollouts and backwards compatibility much more manageable.

Anti-Patterns to Avoid

Even with the best intentions, it’s easy to misuse URL state. Here are common pitfalls:

“State Only in Memory” SPAs

The classic single-page app mistake:

// User hits refresh and loses everything
const [filters, setFilters] = useState({});

If your app forgets its state on refresh, you’re breaking one of the web’s fundamental features. Users expect URLs to preserve context. I remember a viral video from years ago where a Reddit user vented about an e-commerce site: every time she hit “Back,” all her filters disappeared. Her frustration summed it up perfectly. If users lose context, they lose patience.

Sensitive Data in URLs

This one seems obvious, but it’s worth repeating:

// NEVER DO THIS
?password=secret123

URLs are logged everywhere: browser history, server logs, analytics, referrer headers. Treat them as public.

Inconsistent or Opaque Naming

// Unclear and inconsistent
?foo=true&bar=2&x=dark

// Self-documenting and consistent
?mobile=true&page=2&theme=dark

Choose parameter names that make sense. Future you (and your team) will thank you.

Overloading URLs with Complex State

?config=eyJtZXNzYWdlIjoiZGlkIHlvdSByZWFsbHkgdHJpZWQgdG8gZGVjb2RlIHRoYXQ_IiwiZmlsdGVycyI6eyJzdGF0dXMiOlsiYWN0aXZlIiwicGVuZGluZyJdLCJwcmlvcml0eSI6WyJoaWdoIiwibWVkaXVtIl0sInRhZ3MiOlsiZnJvbnRlbmQiLCJyZWFjdCIsImhvb2tzIl0sInJhbmdlIjp7ImZyb20iOiIyMDI0LTAxLTAxIiwidG8iOiIyMDI0LTEyLTMxIn19LCJzb3J0Ijp7ImZpZWxkIjoiY3JlYXRlZEF0Iiwib3JkZXIiOiJkZXNjIn0sInBhZ2luYXRpb24iOnsicGFnZSI6MSwibGltaXQiOjIwfX0==

If you need to base64-encode a massive JSON object, the URL probably isn’t the right place for that state.

URL Length Limits

Browsers and servers impose practical limits on URL length (usually between 2,000 and 8,000 characters) but the reality is more nuanced. As this detailed Stack Overflow answer explains, limits come from a mix of browser behavior, server configurations, CDNs, and even search engine constraints. If you’re bumping against them, it’s a sign you need to rethink your approach.

Breaking the Back Button

// Replacing state incorrectly
history.replaceState({}, '', newUrl); // Used when pushState was needed

Respect browser history. If a user action should be “undoable” via the back button, use pushState. If it’s a refinement, use replaceState.

Closing Thought

That PrismJS URL reminded me of something important: good URLs don’t just point to content. They describe a conversation between the user and the application. They capture intent, preserve context, and enable sharing in ways that no other state management solution can match.

We’ve built increasingly sophisticated state management libraries like Redux, MobX, Zustand, Recoil and others. They all have their place but sometimes the best solution is the one that’s been there all along.

In my previous article, I wrote about the hidden costs of bad URL design. Today, we’ve explored the flip side: the immense value of good URL design. URLs aren’t just addresses. They’re state containers, user interfaces, and contracts all rolled into one.

If your app forgets its state when you hit refresh, you’re missing one of the web’s oldest and most elegant features.