What are Client Hints? Differences Between Client Hints and User-Agent

Understand Client Hints, why they matter, and how they improve privacy and accuracy compared to User-Agent strings. Get clear examples and practical insights—explore smarter browser profiles with Nstbrowser today.

What exactly are Client Hints, and why are they replacing the traditional User-Agent string? If you've ever struggled with inconsistent device detection, unreliable parsing, or rising privacy requirements, Client Hints offer a modern, structured solution. These headers let browsers share precise information—such as platform, device memory, or display settings—only when the server explicitly requests it [1].

In this guide, we break down what Client Hints are, how they work, and provide clear Client Hints examples so you can understand the shift from User-Agent vs Client Hints with confidence. This article helps you adapt to evolving web standards and make better technical decisions.

If you're looking to apply these insights with accuracy and privacy in real workflows, explore how Nstbrowser can elevate your browser profile strategy with purpose—not just action.

What Are Client Hints?

Client Hints are a modern web mechanism that allows browsers to send selective, structured information about the user's device, network, or browser to a website. Instead of sending a large, fixed block of identifying details (like the traditional User-Agent string), Client Hints let the browser share only the data a website explicitly asks for.

In simple terms:

Client Hints = on-demand device information, shared only when the server requests it.

This design gives users better privacy while still allowing websites to optimize content, display formats, and performance for different devices.

Types of Client Hints (With Practical Examples)

Client Hints are grouped into several categories. Here are the most commonly used ones, with real-world examples of how websites may apply them:

1. User Agent Client Hints (UA-CH)

A modern replacement for the traditional User-Agent string:

• Sec-CH-UA: Browser brand and major version (sent by default)
• Sec-CH-UA-Platform: Operating system (sent by default)
• Sec-CH-UA-Platform-Version: Detailed OS version
• Sec-CH-UA-Arch: CPU architecture
• Sec-CH-UA-Model: Device model
• Sec-CH-UA-Mobile: Indicates whether the device is mobile (sent by default)
• Sec-CH-UA-Full-Version-List: Complete list of browser versions

2. Device & Network-Related Hints

• Device-Memory: Amount of device memory
• Downlink: Network downlink speed
• ECT (Effective Connection Type): Connection quality (e.g., 4g, 3g)
• RTT: Round-trip time

3. Display-Related Hints

• Viewport-Width: Width of the viewport
• Width: Intended display width for images
• DPR: Device pixel ratio

4. User Preference Hints

• Sec-CH-Prefers-Color-Scheme: Preference for dark or light mode
• Sec-CH-Prefers-Reduced-Motion: Preference for reduced motion/animations

Browser Support for Client Hints

Client Hints are supported by most modern browsers, but not equally:

• Fully supported: Chrome, Edge, Opera, Brave
• Partial support: Firefox (limited, disabled by default); Safari (Apple prioritizes strict privacy controls)

This uneven support means developers still need fallback strategies—often relying on User Agent parsing when Client Hints are absent.

What Is User-Agent?

The User-Agent string is an older mechanism where the browser sends a long, fixed-format text containing system, browser, and device information.

Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 
(KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36

This single string reveals:

• OS
• Browser type & version
• Rendering engine
• Device architecture

For years, websites relied on User-Agent parsing to:

• Customize layouts
• Detect mobile devices
• Apply compatibility adjustments
• Track or fingerprint users

However, because UA strings expose more information than necessary—and are easy to spoof—modern browsers are moving toward User-Agent Reduction paired with Client Hints [2].

Client Hints vs User-Agent: What's the Difference?

Key Relationship

Client Hints do not fully replace User-Agent yet. Instead:

• Browsers now reduce UA detail
• Websites can optionally request specific information through Client Hints

Think of Client Hints as a more controlled, privacy-friendly evolution of the User-Agent mechanism.

Why Client Hints Matter (Real Use Cases)

Client Hints solve several real-world challenges:

1. Better Privacy with Less Data Exposure

Since browsers only send hints when requested, trackers cannot automatically extract device details. This improves user privacy while still empowering websites with needed info.

2. More Accurate Device Detection

User-Agent strings often lie (for compatibility reasons). Client Hints provide accurate, structured data directly from the browser.

3. Performance Optimization

Websites can adjust content delivery based on:

• Network speed
• Screen resolution
• Device capabilities

This ensures faster loading and better UX.

4. Reliable Multi-Device and Multi-Account Management

Privacy-focused users, automation tools, and multi-account platforms benefit from Client Hints because they reduce unnecessary fingerprinting vectors.

5. Future-Proofing

As major browsers roll out UA Reduction, developers need Client Hints to maintain compatibility and detection features.

Can Client Hints Be Spoofed? The Nstbrowser Solution

Yes, Client Hints can be spoofed, but it's significantly more difficult than manipulating User-Agent strings.

Why are they harder to fake?

• Browsers validate the structure.
• Servers must explicitly request hints.
• Some hints depend on hardware (e.g., DPR, device model).
• Anti-detect tools must simulate multiple layers of environment data consistently.

For ordinary scripts, spoofing Client Hints is not as simple as modifying a single header.

However…

Advanced tools—especially anti-detect browsers like Nstbrowser—can simulate real device environments, including Client Hints. But this requires synchronized spoofing of:

• User-Agent
• Client Hints headers
• JS-exposed properties
• Canvas/WebGL behavior
• Hardware metrics

If any detail is inconsistent, fingerprinting systems can still detect anomalies.

The risk still exists because Client Hints, particularly High-Entropy Hints (like detailed OS version or device model), can still form a highly unique fingerprint—sometimes even more structured than the old User-Agent string [3].

Nstbrowser: Ensuring Client Hint Consistency

For users engaged in multi-accounting, web scraping, or any operation requiring high anonymity, the key is consistency. Nstbrowser is designed to manage this complexity by:

1. Synchronized Spoofing: Nstbrowser ensures that the Client Hints, the User-Agent string, and all JavaScript-exposed properties (which are often used for fingerprinting) are perfectly aligned for each browser profile.
2. Profile Isolation: Each profile is a completely isolated environment, preventing cross-contamination of cookies, local storage, and digital fingerprints.
3. Controlling High-Entropy Data: Nstbrowser allows you to manage the values of high-entropy Client Hints, ensuring that the data presented to the server is both realistic and unique to that specific profile, thus mitigating the risk of account linking [4].

Fingerprint Protection Recommendations

As web fingerprinting becomes more advanced, relying solely on Client Hints or UA spoofing is not enough. Here are practical, actionable tips:

1. Maintain Full Environment Consistency: Every fingerprinting vector—UA, Client Hints, canvas, fonts, WebRTC, timezone—must match one realistic device profile. Random mismatches instantly trigger risk scores.
2. Avoid Manual Modifications: Editing headers manually often causes inconsistencies. Instead, use automated browser profiles where the system generates coherent fingerprints.
3. Use Dynamic User Profiles: Static fingerprints reused across accounts can cause linking. Rotate environment profiles periodically to avoid pattern detection.
4. Disable or Control WebRTC Leaks: Even if your UA and Client Hints are spoofed, a WebRTC IP leak can still expose your identity.
5. Keep Cookies and Storage Isolated: Client Hints do not protect against cookie tracking. Each identity or account should have unique cookies, local storage, and session storage.
6. Use an Anti-detect Browser for Multi-Account or Operational Tasks: Unlike simple extensions, anti-fingerprint browsers like Nstbrowser simulate consistent environments, including Client Hints and modern fingerprint surfaces. This provides stronger protection against account linking and device recognition [5].

Final Thoughts

Client Hints are a major step forward for web privacy and performance. They offer a more precise, controlled alternative to the traditional User-Agent string, helping websites optimize content while reducing unnecessary data exposure.

However, Client Hints alone can't prevent advanced fingerprinting. Real-world environments require consistent spoofing across all device surfaces. For users managing multiple accounts, safeguarding privacy, or avoiding unintended tracking, pairing a robust strategy with an anti-detect browser like Nstbrowser is the most effective solution.

Frequently Asked Questions (FAQ)

Q: What is the main privacy benefit of Client Hints over User-Agent?

A: The main benefit is the "least privilege" principle. The traditional User-Agent string sends a large amount of potentially identifying information (like OS version and browser build) with every request, whether the server needs it or not. Client Hints only send specific, requested information, reducing the overall data footprint and making it harder for passive trackers to collect data.

Q: Are Client Hints a form of fingerprinting?

A: Yes, they can be. While Client Hints are designed to be more privacy-preserving, the High-Entropy Client Hints (e.g., detailed OS version, CPU architecture, device model) provide highly unique data points. If a server requests and combines several of these high-entropy hints, the resulting data can be used to create a very stable and unique browser fingerprint, which is a major concern for privacy advocates.

Q: How does Nstbrowser handle Client Hints?

A: Nstbrowser is designed to manage Client Hints as part of the overall browser fingerprint. For each isolated profile, Nstbrowser ensures that the Client Hints sent are perfectly consistent with the spoofed User-Agent, WebGL, Canvas, and other digital parameters. This prevents the inconsistencies that sophisticated anti-bot systems look for when trying to detect automated or multi-account users.

Q: Will Client Hints eventually replace the User-Agent string entirely?

A: The goal of the User-Agent Reduction initiative is to significantly reduce the information in the User-Agent string, making it less useful for fingerprinting. While the UA string will likely remain in a highly simplified form for backward compatibility, Client Hints are intended to be the primary, structured, and privacy-respecting mechanism for servers to request specific client information going forward.

Q: What are "Low-Entropy" vs "High-Entropy" Client Hints?

A: Low-Entropy Hints are common, less unique data points (like browser brand and major version, or mobile status) that are sent by default. High-Entropy Hints are more unique, detailed data points (like full OS version, CPU architecture, or device model) that are only sent if the server explicitly requests them. High-entropy hints pose a greater risk for fingerprinting.

External Authoritative References

[1] Improving user privacy and developer experience with User-Agent Client Hints - Chrome Developers
[2] User-Agent reduction - MDN Web Docs
[3] HTTP Client hints - MDN Web Docs
[4] What is User-Agent reduction? - Privacy Sandbox
[5] Mitigating Browser Fingerprinting in Web Specifications - W3C